tag:blogger.com,1999:blog-32075479562895709272024-03-18T23:35:48.027-04:00A Medley of PotpourriA Medley of Potpourri is just what it says; various thoughts, opinions, ruminations, and contemplations on a variety of subjects.David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comBlogger22843125tag:blogger.com,1999:blog-3207547956289570927.post-49813237469506166252024-03-18T23:35:00.000-04:002024-03-18T23:35:09.607-04:00Proto-metabolism<p></p><h1 class="firstHeading mw-first-heading" id="firstHeading"><span class="mw-page-title-main"></span></h1>
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Proto-metabolism">https://en.wikipedia.org/wiki/Proto-metabolism</a> </div>
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<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><p>A <b>proto-metabolism</b> is a series of linked chemical reactions in a prebiotic environment that preceded and eventually turned into <a href="https://en.wikipedia.org/wiki/Metabolism" title="Metabolism">modern metabolism</a>. Combining ongoing research in <a href="https://en.wikipedia.org/wiki/Astrobiology" title="Astrobiology">astrobiology</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Prebiotic_chemistry" title="Prebiotic chemistry">prebiotic chemistry</a>, work in this area focuses on reconstructing the connections between potential metabolic processes that may have occurred in <a href="https://en.wikipedia.org/wiki/Early_Earth" title="Early Earth">early Earth</a> conditions. Proto-metabolism is believed to be simpler than modern <a href="https://en.wikipedia.org/wiki/Metabolism" title="Metabolism">metabolism</a> and the <a href="https://en.wikipedia.org/wiki/Last_universal_common_ancestor" title="Last universal common ancestor">Last Universal Common Ancestor (LUCA)</a>, as simple organic molecules likely gave rise to more complex metabolic networks. Prebiotic chemists have demonstrated <a href="https://en.wikipedia.org/wiki/Abiotic_component" title="Abiotic component">abiotic</a> generation of many simple organic molecules including <a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acids</a>,<sup class="reference" id="cite_ref-2"><a href="https://en.wikipedia.org/wiki/Proto-metabolism#cite_note-2">[2]</a></sup> <a href="https://en.wikipedia.org/wiki/Fatty_acid" title="Fatty acid">fatty acids</a>, simple <a href="https://en.wikipedia.org/wiki/Sugar" title="Sugar">sugars</a>, and <a href="https://en.wikipedia.org/wiki/Nucleobase" title="Nucleobase">nucleobases</a>.
There are multiple scenarios bridging prebiotic chemistry to early
metabolic networks that occurred before the origins of life, also known
as <a href="https://en.wikipedia.org/wiki/Abiogenesis" title="Abiogenesis">abiogenesis</a>.
In addition, there are hypotheses made on the evolution of biochemical
pathways including the metabolism-first hypothesis, which theorizes how
reaction networks dissipate <a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy">free energy</a> from which <a href="https://en.wikipedia.org/wiki/Genetics" title="Genetics">genetic</a> molecules and <a href="https://en.wikipedia.org/wiki/Protocell" title="Protocell">proto-cell membranes</a> later emerge.
To determine the composition of key early metabolic networks,
scientists have also used top-down approaches to study LUCA and modern
metabolism.
</p>
<h2><span class="mw-headline" id="Autocatalytic_prebiotic_chemistries">Autocatalytic prebiotic chemistries</span></h2></div></div></div><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Autocatalysis" title="Autocatalysis">Autocatalysis</a> and <a href="https://en.wikipedia.org/wiki/Autocatalytic_set" title="Autocatalytic set">Autocatalytic set</a></div>
<p><a href="https://en.wikipedia.org/wiki/Autocatalysis" title="Autocatalysis">Autocatalytic reactions</a>
are reactions where the reaction product acts as a catalyst for its own
formation. Many researchers that study proto-metabolism agree that
early metabolic networks likely originated as a set of chemical
reactions that form self-sustaining networks. This set of reactions is commonly referred to as an <a href="https://en.wikipedia.org/wiki/Autocatalytic_set" title="Autocatalytic set">autocatalytic set</a>. Some prebiotic chemistries focus on these autocatalytic reactions including the <a href="https://en.wikipedia.org/wiki/Formose_reaction" title="Formose reaction">formose reaction</a>, HCN oligomerization, and formamide chemistry.
</p>
<h3><span class="mw-headline" id="Formose_reaction">Formose reaction</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Formose_reaction" title="Formose reaction">Formose reaction</a></div>
<p>Discovered in 1861 by <a href="https://en.wikipedia.org/wiki/Alexander_Butlerov" title="Alexander Butlerov">Aleksandr Butlerov</a>, the <a href="https://en.wikipedia.org/wiki/Formose_reaction" title="Formose reaction">formose reaction</a> is a set of two reactions converting <a href="https://en.wikipedia.org/wiki/Formaldehyde" title="Formaldehyde">formaldehyde</a> (CH<sub>2</sub>O) to a mixture of simple sugars.
Formaldehyde is an intermediate in the oxidation of simple carbon
molecules (e.g. methane) and was likely present in early Earth's
atmosphere.
The first reaction is the slow conversion of formaldehyde (C1 carbon)
to glycoaldehyde (C2 carbon) and occurs through an unknown mechanism.
The second reaction is the faster and <a href="https://en.wikipedia.org/wiki/Autocatalysis" title="Autocatalysis">autocatalytic</a> formation of higher weight <a href="https://en.wikipedia.org/wiki/Aldose" title="Aldose">aldoses</a> and <a href="https://en.wikipedia.org/wiki/Ketose" title="Ketose">ketoses</a>. The kinetics of the formose reaction are often described as <a href="https://en.wikipedia.org/wiki/Autocatalysis" title="Autocatalysis">autocatalytic</a>, as the <a href="https://en.wikipedia.org/wiki/Alkali" title="Alkali">alkaline</a> reaction uses lowest molecular weight sugars as feedstocks or input molecules into the reaction.
Self-organized autocatalytic networks, like the formose reaction, would
allow for adaptation to changing prebiotic environmental conditions.
As a proof-of-concept, Robinson and colleagues demonstrated how
changing environmental conditions and catalyst availability can impact
the resultant sugar products.
</p><p>In the past, many researchers have suggested the importance of this reaction for <a href="https://en.wikipedia.org/wiki/Abiogenesis" title="Abiogenesis">abiogenesis</a> and the origins of metabolism because it can lead to <a href="https://en.wikipedia.org/wiki/Ribose" title="Ribose">ribose</a>. Ribose is a building block of <a href="https://en.wikipedia.org/wiki/RNA" title="RNA">RNA</a>
and an important precursor in proto-metabolism. However, there are
limitations for the formose reaction to be the chemical origin of sugars
including the low <a href="https://en.wikipedia.org/wiki/Chemoselectivity" title="Chemoselectivity">chemoselectivity</a> for ribose and high complexity of the final reaction mixture.
In addition, a direct joining together of ribose, a nucleobase, and
phosphate to make a ribonucleotide (the building block of RNA) is not
currently chemically feasible. Alternative prebiotic mechanisms have been proposed including <a href="https://en.wikipedia.org/wiki/Cyanosulfidic_prebiotic_synthesis" title="Cyanosulfidic prebiotic synthesis">cyanosulfidic prebiotic chemistries</a>.
</p>
<h3><span class="mw-headline" id="HCN_oligomerization">HCN oligomerization</span></h3><p>On Earth, <a href="https://en.wikipedia.org/wiki/Hydrogen_cyanide" title="Hydrogen cyanide">hydrogen cyanide</a> (HCN) is made in <a href="https://en.wikipedia.org/wiki/Volcano" title="Volcano">volcanos</a>, <a href="https://en.wikipedia.org/wiki/Lightning" title="Lightning">lightning</a>, and <a href="https://en.wikipedia.org/wiki/Reducing_atmosphere" title="Reducing atmosphere">reducing atmospheres</a> like the <a href="https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment" title="Miller–Urey experiment">Miller-Urey experiment</a>. On the Hadean Earth, large impactor events and active <a href="https://en.wikipedia.org/wiki/Hydrothermal_vent" title="Hydrothermal vent">hydrothermal</a> processes likely contributed to widespread metal production and metal-based proto-metabolism. Hydrogen cyanide has also been detected in <a href="https://en.wikipedia.org/wiki/Meteorite" title="Meteorite">meteorites</a> and atmospheres in the outer solar system.
</p><p>HCN-derived polymers are the <a href="https://en.wikipedia.org/wiki/Oligomer" title="Oligomer">oligomer</a> or <a href="https://en.wikipedia.org/wiki/Hydrolysis" title="Hydrolysis">hydrolysis</a> products of HCN.
These polymers can be synthesized from HCN or cyanide salts often in
alkaline conditions, but they have been observed in a wide range of
experimental conditions. HCN readily reacts with itself to produce many HCN polymers and biologically-relevant compounds like <a href="https://en.wikipedia.org/wiki/Nucleobase" title="Nucleobase">nucleobases</a><a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acids</a>, and <a href="https://en.wikipedia.org/wiki/Carboxylic_acid" title="Carboxylic acid">carboxylic acids</a>.
The diversity of products could point to a plausible proto-metabolic
network of HCN oligomerization reactions. Although, some groups point to
low HCN concentrations in early Earth and low chemioselectivity of key
biologically-relevant products, similar to the formose reaction. Others have shown that abundant HCN is produced after large impacts and that high specificity and yield can be achieved.
</p>
<h3><span class="mw-headline" id="Formamide_chemistry">Formamide chemistry</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Formamide-based_prebiotic_chemistry" title="Formamide-based prebiotic chemistry">Formamide-based prebiotic chemistry</a></div>
<p><a href="https://en.wikipedia.org/wiki/Formamide" title="Formamide">Formamide</a> (NH<sub>2</sub>CHO) is the simplest naturally-occurring amide. Similar to HCN, formamide can form naturally.
Formamide has specific physical and stability properties possibly
suitable for a universal prebiotic precursor for early proto-metabolic
networks. For example, it has four <a class="mw-redirect" href="https://en.wikipedia.org/wiki/CHON" title="CHON">universal atomic elements</a>
ubiquitous to life: C, H, O, N. The presence of unique functional
groups involving oxygen and nitrogen support reaction chemistries to
build key biomolecules like amino acids, sugars, nucleosides and other
key intermediates of other prebiotic reactions (e.g. the <a href="https://en.wikipedia.org/wiki/Citric_acid_cycle" title="Citric acid cycle">citric acid cycle</a>). In addition, early Earth geological features like <a href="https://en.wikipedia.org/wiki/Hydrothermal_vent" title="Hydrothermal vent">hydrothermal pores</a> might support formamide chemistry and synthesis of key prebiotic biomolecules with concentration requirements.
</p><p>Overall, formamide chemistry can support connections and
substrates needed to support prebiotic biomolecule synthesis including
the <a href="https://en.wikipedia.org/wiki/Formose_reaction" title="Formose reaction">formose reaction</a>, <a href="https://en.wikipedia.org/wiki/Strecker_amino_acid_synthesis" title="Strecker amino acid synthesis">Strecker synthesis</a>, HCN oligomerization, or the <a href="https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process" title="Fischer–Tropsch process">Fischer-Tropsch process</a>. In addition, formamide can be easily concentrated through <a href="https://en.wikipedia.org/wiki/Evaporation" title="Evaporation">evaporation reactions</a> as it has a boiling point of 210C. Although this reaction has high versatility across one-carbon atom
precursors, the connections between different biosynthetic pathways are
yet to be directly explored experimentally.
</p>
<h2><span class="mw-headline" id="Experimental_reconstruction">Experimental reconstruction</span></h2><p>Many
research groups are actively attempting experimental reconstruction of
the interactions between prebiotic reactions. One major consideration is
the ability for these reactions to operate in the same environmental
conditions. These one-pot syntheses would likely push the reaction towards specific subgroups of moleculesThe key to building proto-metabolic scenarios involves coupling constructive and interconversion reactions. <b>Constructive reactions</b> use <a href="https://en.wikipedia.org/wiki/Autocatalysis" title="Autocatalysis">autocatalytic</a> prebiotic chemistries to increase the structural complexity of the original molecule, while <b>interconversion reactions</b> connect different prebiotic chemistries by changing the <a href="https://en.wikipedia.org/wiki/Functional_group" title="Functional group">functional groups</a>
appended to the original molecule. A functional group is a group of
atoms that has similar properties whenever it appears in different
molecules. These interconversion reactions and functional group
transformations can lead to new prebiotic chemistries and precursor
molecules.
</p>
<h3><span class="mw-headline" id="Cyanosulfidic_scenario">Cyanosulfidic scenario</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cyanosulfidic_Prebiotic_Synthesis" title="Cyanosulfidic Prebiotic Synthesis">Cyanosulfidic Prebiotic Synthesis</a></div>
<p>Cyanosulfidic scenarios are mechanisms for proto-metabolism proposed by the <a href="https://en.wikipedia.org/wiki/Albert_Eschenmoser" title="Albert Eschenmoser">Eschenmoser</a> and <a href="https://en.wikipedia.org/wiki/John_Sutherland_(chemist)" title="John Sutherland (chemist)">Sutherland</a> groups. Research from the Eschenmoser group suggested that interactions between
HCN and aldehydes can catalyze the formation of diaminomaleodinitrile
(DAMN). Iterations of this cycle would generate multiple intermediate
metabolites and key biomolecular precursors through functional group
transformations by hydrolytic and redox processes. To expand upon this
finding, the Sutherland group experimentally assessed the assembly of
biomolecular building blocks from prebiotic intermediates and one-carbon
feedstocks.
They synthesized precursors of ribonucleotides, amino acids and lipids
from the reactants of hydrogen cyanide, acetylene, acrylonitrile
(product of cyanide and acetylene), and dihydroxyacetone (stable <a href="https://en.wikipedia.org/wiki/Triose" title="Triose">triose</a> isomer of glyceraldehyde and phosphate). These reactions are driven by UV light and use hydrogen sulfide (H<sub>2</sub>S) as the primary <a href="https://en.wikipedia.org/wiki/Reducing_agent" title="Reducing agent">reductant</a>
in these reactions. As each of these synthesis reactions was tested
independently and some reactions require periodic input of additional
reactants, these biomolecular precursors were not strictly generated
through a <a href="https://en.wikipedia.org/wiki/One-pot_synthesis" title="One-pot synthesis">one-pot synthesis</a> expected of early Earth environments. In the same work, these authors argue that <a href="https://en.wikipedia.org/wiki/Flow_chemistry" title="Flow chemistry">flow chemistry</a> or the movement of reactants through water could generate the conditions favorable for the synthesis of these molecules.
</p>
<h3><span class="mw-headline" id="Glyoxylate_scenario">Glyoxylate scenario</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/TCA_cycle" title="TCA cycle">TCA cycle</a></div><p>Eschenmoser
also proposed a parallel scenario where the connections between
prebiotic reactions would be connected by glyoxylate, a simple
α-ketoacid, produced by HCN oligomerization and hydrolysis.
In this work, Eschenmoser proposes potential schemes to generate both
informational oligomers and other key autocatalytic reactions from
plausible one-carbon sources (HCN, CO, CO<sub>2</sub>).
</p><p>The Krishnamurthy group at Scripps experimentally expanded on this theory. In mild aqueous conditions, they demonstrated that the reaction of glyoxylate and pyruvate can produce a series of α-<a href="https://en.wikipedia.org/wiki/Keto_acid" title="Keto acid">ketoacid</a> intermediates constituting the <a href="https://en.wikipedia.org/wiki/Reverse_Krebs_cycle" title="Reverse Krebs cycle">reductive tricarboxylic acid (TCA) cycle</a>.
This reaction proceeded without metal or enzyme catalysts as glyoxylate
acted as both the carbon source and reducing agent in the reaction.
Similarly, the Moran group have also reported pyruvate and glyoxylate
can react in warm iron-rich water to produce TCA intermediates and some
amino acids. Their work has successfully reconstructed 9 out of 11 TCA intermediates and 5 universal metabolic precursors. Additional experimental analysis is needed to connect this scenario to modern metabolism.
</p>
<h2><span class="mw-headline" id="Energy_sources">Energy sources</span></h2><p>Unlike
proto-metabolism, the bioenergetic pathways powering modern metabolism
are well understood. In early Earth conditions, there were mainly three
kinds of energy to support early metabolic pathways: high energy sources
to catalyze monomers, lower energy sources to support <a href="https://en.wikipedia.org/wiki/Condensation" title="Condensation">condensation</a> or <a href="https://en.wikipedia.org/wiki/Polymerization" title="Polymerization">polymerization</a>, and energy carriers that support transfer of energy from the environment to metabolic networks. Examples of high energy sources include <a href="https://en.wikipedia.org/wiki/Photochemistry" title="Photochemistry">photochemical</a> energy from <a href="https://en.wikipedia.org/wiki/Ultraviolet" title="Ultraviolet">ultraviolet light</a>, <a href="https://en.wikipedia.org/wiki/Electric_discharge" title="Electric discharge">atmospheric electric discharge</a>, and <a href="https://en.wikipedia.org/wiki/Geology" title="Geology">geological</a> <a href="https://en.wikipedia.org/wiki/Electrochemistry" title="Electrochemistry">electrochemical</a>
energy. These energy sources would support synthesis of biological
monomers or feedstocks for proto-metabolism. In contrast, examples of
lower energy sources for assembly of more complex molecules include
anhydrous heat, mineral-catalyzed synthesis, and sugar-driven reactions.
Energy carrier molecules could allow for propagation of the energy
through the metabolic networks likely resembled modern energy carriers
including <a href="https://en.wikipedia.org/wiki/Adenosine_triphosphate" title="Adenosine triphosphate">ATP</a> and <a href="https://en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleotide" title="Nicotinamide adenine dinucleotide">NADH</a>. Both energy carriers are nucleotide-based molecules and likely originated early in metabolism.
</p>
<h2><span class="mw-headline" id="Metabolism-first_hypothesis">Metabolism-first hypothesis</span></h2><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Abiogenesis" title="Abiogenesis">Abiogenesis</a></div>
<p>Metabolism-first hypothesis suggests that autocatalytic networks of metabolic reactions were the first forms of life. This is an alternative hypothesis to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/RNA_World_Hypothesis" title="RNA World Hypothesis">RNA-world</a>, which is a genes-first hypothesis. It was first proposed by <a href="https://en.wikipedia.org/wiki/Martynas_Y%C4%8Das" title="Martynas Yčas">Martynas Ycas</a> in 1955. Many recent work in this area is focused in computational modeling of theoretical prebiotic networks.
</p><p>Metabolism-first proponents postulate that <a href="https://en.wikipedia.org/wiki/Self-replication" title="Self-replication">replication</a> and genetic machinery could not arise without the accumulation of the molecules needed for replication. Alone, simple connections between prebiotic synthesis reactions could form key organic molecules and once encapsulated by a <a href="https://en.wikipedia.org/wiki/Cell_membrane" title="Cell membrane">membrane</a>
would constitute the first cells. These reactions could be catalyzed by
various inorganic molecules or ions and stabilized by solid surfaces. Molecular self-replicators and enzymes would emerge later, with these future metabolisms better resembling modern metabolism.
</p><p>One critique for the metabolism-first hypothesis for abiogenesis
is they would also need self-replicating abilities with a high degree of
fidelity.
If not, the chemical networks with greater fitness in early Earth would
not be preserved. There is limited experimental evidence for these
theories, so additional exploration in this area is needed to determine
the feasibility of a metabolism-first origins of life.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-70105374737356986372024-03-18T15:54:00.006-04:002024-03-18T15:54:59.629-04:00Visual agnosia<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><b> <br /></b></div><div class="noprint" id="siteSub"><b>Visual agnosia</b> is an impairment in recognition of visually
presented objects. It is not due to a deficit in vision (acuity, visual
field, and scanning), language, memory, or intellect. While <a href="https://en.wikipedia.org/wiki/Cortical_blindness" title="Cortical blindness">cortical blindness</a>
results from lesions to primary visual cortex, visual agnosia is often
due to damage to more anterior cortex such as the posterior <a href="https://en.wikipedia.org/wiki/Occipital_lobe" title="Occipital lobe">occipital</a> and/or <a href="https://en.wikipedia.org/wiki/Temporal_lobe" title="Temporal lobe">temporal lobe</a>(s) in the brain. There are two types of visual agnosia: apperceptive agnosia and associative agnosia.
</div></div><div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cognitive_neuroscience_of_visual_object_recognition" title="Cognitive neuroscience of visual object recognition">Recognition of visual objects</a>
occurs at two primary levels. At an apperceptive level, the features of
the visual information from the retina are put together to form a
perceptual representation of an object. At an associative level, the
meaning of an object is attached to the perceptual representation and
the object is identified.
If a person is unable to recognize objects because they cannot perceive
correct forms of the objects, although their knowledge of the objects
is intact (i.e. they do not have <a href="https://en.wikipedia.org/wiki/Anomic_aphasia" title="Anomic aphasia">anomia</a>),
they have apperceptive agnosia. If a person correctly perceives the
forms and has knowledge of the objects, but cannot identify the objects,
they have associative agnosia.
</p>
<h2><span class="mw-headline" id="Symptoms_and_signs">Symptoms and signs</span></h2></div></div></div><p>While
most cases of visual agnosia are seen in older adults who have
experienced extensive brain damage, there are also cases of young
children with less brain damage during developmental years acquiring the
symptoms.
Commonly, visual agnosia presents as an inability to recognize an
object in the absence of other explanations, such as blindness or
partial blindness, anomia, memory loss, etc. Other common manifestations
of visual agnosia that are generally tested for include difficulty
identifying objects that look similar in shape, difficulty with
identifying line drawings of objects, and recognizing objects that are
shown from less common views, such as a horse from a top-down view.
</p><p>Within any given patient, a variety of symptoms can occur, and
the impairment of ability is not only binary but can range in severity.
For example, Patient SM is a <a href="https://en.wikipedia.org/wiki/Prosopagnosia" title="Prosopagnosia">prosopagnosic</a>
with a unilateral lesion to left extrastriate cortex due to an accident
in his twenties who displays behavior similar to congenital <a href="https://en.wikipedia.org/wiki/Prosopagnosia" title="Prosopagnosia">prosopagnosia</a>.
Although he can recognize facial features and emotions – indeed he
sometimes uses a standout feature to recognize a face – face recognition
is almost impossible purely from visual stimuli, even for faces of
friends, family, and himself. The disorder also affects his memory of
faces, both in storing new memories of faces and recalling stored
memories.
</p><p>Nevertheless, it is important to note the reach of symptoms to
other domains. SM's object recognition is similarly impaired though not
entirely; when given line drawings to identify, he was able to give
names of objects with properties similar to the drawing, implying that
he is able to see the features of the drawing. Similarly, copying a
line drawing of a beach scene led to a simplified version of the
drawing, though the main features were accounted for. For recognition of
places, he is still impaired but familiar places are remembered and new
places can be stored into memory.
</p>
<h2><span class="mw-headline" id="Pathophysiology">Pathophysiology</span></h2><p>Visual
agnosia occurs after damage to visual association cortex or to parts of
the ventral stream of vision, known as the "what pathway" of vision for
its role in object recognition.
This occurs even when no damage has been done to the eyes or optic
tract that leads visual information into the brain; in fact, visual
agnosia occurs when symptoms cannot be explained by such damage. Damage
to specific areas of the ventral stream impair the ability to recognize
certain categories of visual information, such as the case of
prospagnosia.
Patients with visual agnosia generally do not have damage to the
dorsal stream of vision, known as the "where pathway" of vision because
of its role determining object's position in space, allowing individuals
with visual agnosia to show relatively normal visually guided behavior.
</p><p>For example, patient DF had lesions to the ventral surface that gave her apperceptive agnosia. One of the tasks she was tested on required her to place a card through
a thin slot that could be rotated into all orientations. As an
apperceptive agnosic, it would be expected that since she cannot
recognize the slot, she should not be able to correctly place the card
into the slot. Indeed, when she was asked to give the direction of the
slot, her responses were no better than chance. Yet, when she was asked
to place the card into the slot, her success was almost to the level of
the controls. This implies that in the event of a ventral stream
deficit, the dorsal stream can help with processing of special
information to aid movement regardless of object recognition.
</p><p>More specifically, the lateral occipital complex appears to respond to many different types of objects.
Prosopagnosia (inability to recognize faces) is due to damage of the
fusiform face area (FFA). An area in the fusiform gyrus of the temporal
lobe that has been strongly associated with a role in facial
recognition.
However, this area is not exclusive to faces; recognition of other
objects of expertise are also processed in this area. The extrastriate
body cortex (EBA) was found to be activated by photographs, silhouettes,
or stick drawings of human bodies.
The parahippocampal place area (PPA) of the limbic cortex has been
found to be activated by the sight of scenes and backgrounds.
Cerebral achromatopsia (the inability to discriminate between
different hues) is caused by damage to the V8 area of the visual
association cortex.
</p><p>The left hemisphere seems to play a critical role in recognizing the meaning of common objects.
</p>
<h2><span class="mw-headline" id="Diagnosis">Diagnosis</span></h2><h3><span class="mw-headline" id="Classification">Classification</span></h3><p>Broadly, visual agnosia is divided into apperceptive and associative visual agnosia.
</p><p>Apperceptive agnosia is failure of object recognition even when
the basic visual functions (acuity, color, motion) and other mental
processing, such as language and intelligence, are normal.
The brain must correctly integrate features such as edges, light
intensity, and color from sensory information to form a complete percept
of an object. If a failure occurs during this process, a percept of an
object is not fully formed and thus it cannot be recognized.
Tasks requiring copying, matching, or drawing simple figures can
distinguish the individuals with apperceptive agnosia because they
cannot perform such tasks.
</p><p>Associative agnosia is an inability to identify objects even with
apparent perception and knowledge of them. It involves a higher level
of processing than apperceptive agnosia.
Individuals with associative agnosia can copy or match simple figures,
indicating that they can perceive objects correctly. They also display
the knowledge of objects when tested with tactile or verbal information.
However, when tested visually, they cannot name or describe common
objects. This means that there is an impairment in associating the perception of objects with the stored knowledge of them.
</p><p>Although visual agnosia can be general, there exist many variants
that impair recognition of specific types. These variants of visual
agnosia include prosopagnosia (inability to recognize faces), pure word
blindness (inability to recognize words, often called "agnosic alexia"
or "pure alexia"), agnosias for colors (inability to differentiate
colors), agnosias for the environment (inability to recognize landmarks
or difficulty with spatial layout of an environment, i.e.
topographagnosia) and simultanagnosia (inability to sort out multiple
objects in a visual scene).
</p>
<h4><span class="mw-headline" id="Categories_and_subtypes_of_visual_agnosia">Categories and subtypes of visual agnosia</span></h4><p>The two main categories of visual agnosia are:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Apperceptive_agnosia" title="Apperceptive agnosia">Apperceptive visual agnosia</a>, impaired object recognition. Individuals with apperceptive visual agnosia cannot form a whole percept of visual information.</li><li><a href="https://en.wikipedia.org/wiki/Associative_visual_agnosia" title="Associative visual agnosia">Associative visual agnosia</a>,
impaired object identification. Individuals with associative agnosia
cannot give a meaning to a formed percept. The percept is created, but
it would have no meaning for individuals who have an associative
agnosia.</li></ul>
<h5><span class="mw-headline" id="Subtypes_of_associative_visual_agnosia">Subtypes of associative visual agnosia</span></h5><ul><li><a href="https://en.wikipedia.org/wiki/Achromatopsia" title="Achromatopsia">Achromatopsia</a>, an inability to distinguish different <a href="https://en.wikipedia.org/wiki/Color" title="Color">colors</a>.</li><li><a href="https://en.wikipedia.org/wiki/Prosopagnosia" title="Prosopagnosia">Prosopagnosia</a>, an inability to recognize human faces.
Individuals with prosopagnosia know that they are looking at faces, but
cannot recognize people by the sight of their face, even people whom
they know well.</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Simultagnosia" title="Simultagnosia">Simultagnosia</a>,
an inability to recognize multiple objects in a scene, including
distinct objects within a spatial layout and distinguishing between
"local" objects and "global" objects, such as being able to see a tree
but not the forest or vice versa.</li><li>Topographagnosia, an inability to process the spatial layout of an
environment, including landmark agnosia, difficulty recognizing
buildings and places; difficulty building mental maps of a location or
scene; and/or an inability to discern the orientation between objects in
space.</li><li>Pure alexia, an inability to read.</li><li>Orientation agnosia: an inability to judge or determine orientation of objects.</li><li>Pantomime agnosia: an inability to understand pantomimes (gestures).
It appears that the inferior cortical visual cortex is critical in
recognizing pantomimes.</li></ul>
<h2><span class="mw-headline" id="Patient_CK">Patient CK</span></h2><h3><span class="mw-headline" id="Background">Background</span></h3><p>Patient
C.K. was born in 1961 in England and emigrated to Canada in 1980. In
January 1988, C.K. sustained a head injury from a motor vehicle accident
while out for a jog. Following the accident, C.K. experienced many
cognitive issues, mood swings, poor memory, and temper outbursts. C.K.
also had motor weakness on the left side and a left homonymous
hemianopia. He recovered well, retaining normal intelligence and normal
visual acuity. He was able to complete a master's degree in history,
later working as a manager at a large corporation. Although his recovery
was successful in other areas of cognition, C.K. still struggles to
make sense of the visual world.
</p>
<h3><span class="mw-headline" id="Associative_visual_agnosia">Associative visual agnosia</span></h3><p>Magnetic
resonance imaging (MRI) showed bilateral thinning of C.K.'s occipital
lobe which resulted in associative visual agnosia.
Patients that have visual agnosia are unable to identify visually
presented objects. They can identify these objects through other
modalities such as touch but if presented visually, they are unable to.
Associative agnosic patients cannot create a detailed representation of
the visual world in their brains, they can only perceive elements of
whole objects. They also cannot form associations between objects or assign meaning to objects.
</p><p>C.K. makes many mistakes when trying to identify objects. For
example, he called an abacus "skewers on a kebab" and a badminton
racquet a "fencer's mask". A dart was a "feather duster" and a
protractor was mistaken for a "cockpit". Despite this impairment in
visual object recognition, C.K. retained many abilities such as drawing,
visual imagery, and internal imagery. As a native of England, he was
tasked with drawing England, marking London and where he was born. His
accurate drawing of England is just one example of his excellent drawing
abilities.
</p><p>As aforementioned, C.K. is able to identify parts of objects but
cannot generate a whole representation. It should not be surprising then
that his visual imagery for object size, shape, and color is intact.
For example, when shown a picture of an animal, he can correctly answer
questions such as "are the ears up or down?" and "is the tail long or
short?" He can correctly identify colors, for example that the inside of
a cantaloupe is orange.<sup class="reference" id="cite_ref-pmid7964528_19-4"><a href="https://en.wikipedia.org/wiki/Visual_agnosia#cite_note-pmid7964528-19">[19]</a></sup>
Finally, C.K. can generate internal images and perceive these generated
objects. For example, Finke, Pinker, and Farah instructed C.K. to
imagine a scenario where a 'B' is rotated 90 degrees to the left, a
triangle is put below, and the line in the middle is removed. C.K. can
correctly identify this object as a heart by picturing this
transformation in his head.
</p>
<h3><span class="mw-headline" id="Evidence_for_double_dissociation_between_face_and_object_processing">Evidence for double dissociation between face and object processing</span></h3><p>Patient C.K. provided evidence for a double dissociation between face processing and visual object processing. Patients with <a href="https://en.wikipedia.org/wiki/Prosopagnosia" title="Prosopagnosia">prosopagnosia</a>
have damage to the Fusiform Face Area (FFA) and are unable to recognize
upright faces. C.K. has no difficulty with face processing and matches
the performance of controls when tasked with identifying upright famous
faces. When shown inverted faces of famous people, C.K. performs
significantly worse than controls. This is because processing inverted
faces involves a piecemeal strategy. C.K.'s performance is compared to
patients with prosopagnosia who are impaired in face processing but
perform well identifying inverted faces. This was the first evidence for
a double dissociation between face and object processing suggesting a
face-specific processing system. <span class="mw-headline" id="In_popular_culture">In popular culture</span></p><ul><li>A famous report on this condition is the title essay of <a href="https://en.wikipedia.org/wiki/Oliver_Sacks" title="Oliver Sacks">Oliver Sacks</a>' book, <i><a href="https://en.wikipedia.org/wiki/The_Man_Who_Mistook_His_Wife_for_a_Hat" title="The Man Who Mistook His Wife for a Hat">The Man Who Mistook His Wife for a Hat</a></i>.</li><li>The murder suspect in the <i><a href="https://en.wikipedia.org/wiki/Picket_Fences" title="Picket Fences">Picket Fences</a></i> episode "Strangers" supposedly had agnosia.</li><li>The patient in the <i><a href="https://en.wikipedia.org/wiki/House_(TV_series)" title="House (TV series)">House</a></i> episode "<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Adverse_Events" title="Adverse Events">Adverse Events</a>" had agnosia.</li><li>In the graphic novel <i><a href="https://en.wikipedia.org/wiki/Preacher_(comics)" title="Preacher (comics)">Preacher</a></i>,
the character Lorie has an extreme version of agnosia resulting from
being born with a single eye. For example, she perceives Arseface, a man
with severe facial deformities, as resembling a young <a href="https://en.wikipedia.org/wiki/James_Dean" title="James Dean">James Dean</a>.</li><li>Val Kilmer's character has visual agnosia in the film <i><a href="https://en.wikipedia.org/wiki/At_First_Sight_(1999_film)" title="At First Sight (1999 film)">At First Sight</a></i>.</li><li>In "Folie à Deux", a fifth-season episode of <i><a href="https://en.wikipedia.org/wiki/The_X-Files" title="The X-Files">The X-Files</a></i>,
Mulder succumbs to the same belief as telemarketer Gary Lambert, that
his boss Greg Pincus is a monster who disguises his true appearance by
means of <a href="https://en.wikipedia.org/wiki/Hypnosis" title="Hypnosis">hypnosis</a>.
Scully, although believing this notion preposterous, suggests that what
Mulder describes is analogous to an induced visual agnosia.</li><li>The short story "<a href="https://en.wikipedia.org/wiki/Liking_What_You_See:_A_Documentary" title="Liking What You See: A Documentary">Liking What You See: A Documentary</a>" by <a href="https://en.wikipedia.org/wiki/Ted_Chiang" title="Ted Chiang">Ted Chiang</a> examines the cultural effects of a noninvasive medical procedure that induces a visual agnosia toward physical beauty.</li></ul>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-4339513045603365452024-03-18T15:46:00.000-04:002024-03-18T15:46:12.005-04:00Microorganism<div aria-labelledby="firstHeading" class="vector-body ve-init-mw-desktopArticleTarget-targetContainer" data-mw-ve-target-container="" id="bodyContent"><div class="vector-body-before-content"><div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
</div><div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><a href="https://en.wikipedia.org/wiki/Microorganism">https://en.wikipedia.org/wiki/Microorganism</a><br /><figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:E_coli_at_10000x,_original.jpg"><img class="mw-file-element" data-file-height="1889" data-file-width="2598" height="291" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/E_coli_at_10000x%2C_original.jpg/250px-E_coli_at_10000x%2C_original.jpg" width="400" /></a><figcaption>A <a href="https://en.wikipedia.org/wiki/Colony_(biology)#Microbial_colonies" title="Colony (biology)">cluster</a> of <i><a href="https://en.wikipedia.org/wiki/Escherichia_coli" title="Escherichia coli">Escherichia coli</a></i> <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">bacteria</a> magnified 10,000 times</figcaption></figure>
</div></div></div>A <b>microorganism</b>, or <b>microbe</b>, is an <a href="https://en.wikipedia.org/wiki/Organism" title="Organism">organism</a> of <a href="https://en.wikipedia.org/wiki/Microscopic_scale" title="Microscopic scale">microscopic</a> size, which may exist in its <a href="https://en.wikipedia.org/wiki/Unicellular_organism" title="Unicellular organism">single-celled</a> form or as a <a href="https://en.wikipedia.org/wiki/Colony_(biology)#Microbial_colonies" title="Colony (biology)">colony of cells</a>.
<p>The possible existence of unseen microbial life was suspected from ancient times, such as in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jain_scriptures" title="Jain scriptures">Jain scriptures</a> from sixth century BC India. The scientific study of microorganisms began with their observation under the <a href="https://en.wikipedia.org/wiki/Microscope" title="Microscope">microscope</a> in the 1670s by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Anton_van_Leeuwenhoek" title="Anton van Leeuwenhoek">Anton van Leeuwenhoek</a>. In the 1850s, <a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> found that microorganisms caused <a href="https://en.wikipedia.org/wiki/Food_spoilage" title="Food spoilage">food spoilage</a>, debunking the theory of <a href="https://en.wikipedia.org/wiki/Spontaneous_generation" title="Spontaneous generation">spontaneous generation</a>. In the 1880s, <a href="https://en.wikipedia.org/wiki/Robert_Koch" title="Robert Koch">Robert Koch</a> discovered that microorganisms caused the diseases <a href="https://en.wikipedia.org/wiki/Tuberculosis" title="Tuberculosis">tuberculosis</a>, <a href="https://en.wikipedia.org/wiki/Cholera" title="Cholera">cholera</a>, <a href="https://en.wikipedia.org/wiki/Diphtheria" title="Diphtheria">diphtheria</a>, and <a href="https://en.wikipedia.org/wiki/Anthrax" title="Anthrax">anthrax</a>.
</p><p>Because microorganisms include most <a href="https://en.wikipedia.org/wiki/Unicellular_organism" title="Unicellular organism">unicellular organisms</a> from all <a href="https://en.wikipedia.org/wiki/Three-domain_system" title="Three-domain system">three domains of life</a> they can be extremely diverse. Two of the three domains, <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">Archaea</a> and <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">Bacteria</a>, only contain microorganisms. The third domain <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eukaryota" title="Eukaryota">Eukaryota</a> includes all <a href="https://en.wikipedia.org/wiki/Multicellular_organism" title="Multicellular organism">multicellular organisms</a> as well as many unicellular <a href="https://en.wikipedia.org/wiki/Protist" title="Protist">protists</a> and <a href="https://en.wikipedia.org/wiki/Protozoa" title="Protozoa">protozoans</a> that are microbes. Some protists are related to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Animals" title="Animals">animals</a> and some to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Green_plants" title="Green plants">green plants</a>. There are also many multicellular organisms that are microscopic, namely <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Micro-animal" title="Micro-animal">micro-animals</a>, some <a href="https://en.wikipedia.org/wiki/Fungus" title="Fungus">fungi</a>, and some <a href="https://en.wikipedia.org/wiki/Algae" title="Algae">algae</a>, but these are generally not considered microorganisms.
</p><p>Microorganisms can have very different <a href="https://en.wikipedia.org/wiki/Habitat" title="Habitat">habitats</a>, and live everywhere from the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Geographic_pole" title="Geographic pole">poles</a> to the <a href="https://en.wikipedia.org/wiki/Equator" title="Equator">equator</a>, <a href="https://en.wikipedia.org/wiki/Desert" title="Desert">deserts</a>, <a href="https://en.wikipedia.org/wiki/Geyser" title="Geyser">geysers</a>, <a href="https://en.wikipedia.org/wiki/Rock_(geology)" title="Rock (geology)">rocks</a>, and the <a href="https://en.wikipedia.org/wiki/Deep_sea" title="Deep sea">deep sea</a>. Some are <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Extremophiles" title="Extremophiles">adapted to extremes</a> such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hyperthermophiles" title="Hyperthermophiles">very hot</a> or <a href="https://en.wikipedia.org/wiki/Psychrophile" title="Psychrophile">very cold conditions</a>, others to <a href="https://en.wikipedia.org/wiki/Piezophile" title="Piezophile">high pressure</a>, and a few, such as <i><a href="https://en.wikipedia.org/wiki/Deinococcus_radiodurans" title="Deinococcus radiodurans">Deinococcus radiodurans</a></i>, to <a href="https://en.wikipedia.org/wiki/Radioresistance" title="Radioresistance">high radiation</a> environments. Microorganisms also make up the <a href="https://en.wikipedia.org/wiki/Microbiota" title="Microbiota">microbiota</a> found in and on all multicellular organisms. There is evidence that 3.45-billion-year-old <a href="https://en.wikipedia.org/wiki/Australia" title="Australia">Australian</a> rocks once contained microorganisms, the earliest direct evidence of life on Earth.
</p><p>Microbes are <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Microbes_in_human_culture" title="Microbes in human culture">important in human culture</a> and <a href="https://en.wikipedia.org/wiki/Health" title="Health">health</a> in many ways, serving to <a href="https://en.wikipedia.org/wiki/Fermentation_in_food_processing" title="Fermentation in food processing">ferment foods</a> and <a href="https://en.wikipedia.org/wiki/Sewage_treatment" title="Sewage treatment">treat sewage</a>, and to <a href="https://en.wikipedia.org/wiki/Algae_fuel" title="Algae fuel">produce fuel</a>, <a href="https://en.wikipedia.org/wiki/Enzyme" title="Enzyme">enzymes</a>, and other <a href="https://en.wikipedia.org/wiki/Bioactive_compound" title="Bioactive compound">bioactive compounds</a>. Microbes are essential tools in <a href="https://en.wikipedia.org/wiki/Biology" title="Biology">biology</a> as <a href="https://en.wikipedia.org/wiki/Model_organism" title="Model organism">model organisms</a> and have been put to use in <a href="https://en.wikipedia.org/wiki/Biological_warfare" title="Biological warfare">biological warfare</a> and <a href="https://en.wikipedia.org/wiki/Bioterrorism" title="Bioterrorism">bioterrorism</a>. Microbes are a vital <a href="https://en.wikipedia.org/wiki/Soil_microbiology" title="Soil microbiology">component of fertile soil</a>. In the <a href="https://en.wikipedia.org/wiki/Human_body" title="Human body">human body</a>, microorganisms make up the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Human_microbiota" title="Human microbiota">human microbiota</a>, including the essential <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gut_flora" title="Gut flora">gut flora</a>. The <a href="https://en.wikipedia.org/wiki/Pathogen" title="Pathogen">pathogens</a> responsible for many <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Infectious_disease" title="Infectious disease">infectious diseases</a> are microbes and, as such, are the target of <a href="https://en.wikipedia.org/wiki/Hygiene" title="Hygiene">hygiene measures</a>.
</p>
<h2><span class="mw-headline" id="Discovery">Discovery</span></h2><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/History_of_biology" title="History of biology">History of biology</a> and <a href="https://en.wikipedia.org/wiki/Microbiology#History" title="Microbiology">Microbiology § History</a></div>
<h3><span class="mw-headline" id="Ancient_precursors">Ancient precursors</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Mahaveer_swami.jpg"><img class="mw-file-element" data-file-height="285" data-file-width="240" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Mahaveer_swami.jpg/170px-Mahaveer_swami.jpg" width="337" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Mahavira" title="Mahavira">Mahavira</a> postulated the existence of microscopic creatures in the <a href="https://en.wikipedia.org/wiki/6th_century_BC" title="6th century BC">6th century BC</a></figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Anthonie_van_Leeuwenhoek_(1632-1723)._Natuurkundige_te_Delft_Rijksmuseum_SK-A-957.jpeg"><img class="mw-file-element" data-file-height="2547" data-file-width="2148" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Anthonie_van_Leeuwenhoek_%281632-1723%29._Natuurkundige_te_Delft_Rijksmuseum_SK-A-957.jpeg/170px-Anthonie_van_Leeuwenhoek_%281632-1723%29._Natuurkundige_te_Delft_Rijksmuseum_SK-A-957.jpeg" width="337" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek" title="Antonie van Leeuwenhoek">Antonie van Leeuwenhoek</a> was the first to study microscopic organisms.</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Spallanzani.jpg"><img class="mw-file-element" data-file-height="1043" data-file-width="817" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Spallanzani.jpg/170px-Spallanzani.jpg" width="313" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Lazzaro_Spallanzani" title="Lazzaro Spallanzani">Lazzaro Spallanzani</a> showed that boiling a broth stopped it from decaying.</figcaption></figure>
<p>The possible existence of microscopic organisms was discussed for
many centuries before their discovery in the seventeenth century. By the
<a href="https://en.wikipedia.org/wiki/6th_century_BC" title="6th century BC">6th century BC</a>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jain" title="Jain">Jains</a> of present-day India postulated the existence of tiny organisms called <a href="https://en.wikipedia.org/wiki/Nigoda" title="Nigoda">nigodas</a>.
These nigodas are said to be born in clusters; they live everywhere,
including the bodies of plants, animals, and people; and their life
lasts only for a fraction of a second. According to <a href="https://en.wikipedia.org/wiki/Mahavira" title="Mahavira">Mahavira</a>, the 24th preacher of Jainism, the humans destroy these nigodas on a massive scale, when they eat, breathe, sit, and move. Many modern Jains assert that Mahavira's teachings presage the existence of microorganisms as discovered by modern science.
</p><p>The earliest known idea to indicate the possibility of diseases spreading by yet unseen organisms was that of the <a href="https://en.wikipedia.org/wiki/Ancient_Rome" title="Ancient Rome">Roman</a> scholar <a href="https://en.wikipedia.org/wiki/Marcus_Terentius_Varro" title="Marcus Terentius Varro">Marcus Terentius Varro</a> in a first-century BC book entitled <i>On Agriculture</i> in which he called the unseen creatures animalia minuta, and warns against locating a homestead near a swamp:
</p>
<blockquote class="templatequote"><p>… and because there are bred
certain minute creatures that cannot be seen by the eyes, which float in
the air and enter the body through the mouth and nose and they cause
serious diseases.</p></blockquote>
<p>In <i><a href="https://en.wikipedia.org/wiki/The_Canon_of_Medicine" title="The Canon of Medicine">The Canon of Medicine</a></i> (1020), <a href="https://en.wikipedia.org/wiki/Avicenna" title="Avicenna">Avicenna</a> suggested that <a href="https://en.wikipedia.org/wiki/Tuberculosis" title="Tuberculosis">tuberculosis</a> and other diseases might be contagious.
</p>
<h3><span class="mw-headline" id="Early_modern">Early modern</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Microscopic_discovery_of_bacteria" title="Microscopic discovery of bacteria">Microscopic discovery of bacteria</a></div>
<p>Turkish scientist <a href="https://en.wikipedia.org/wiki/Akshamsaddin" title="Akshamsaddin">Akshamsaddin</a> mentioned the microbe in his work <i>Maddat ul-Hayat</i> (The Material of Life) about two centuries prior to <a href="https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek" title="Antonie van Leeuwenhoek">Antonie van Leeuwenhoek</a>'s discovery through experimentation:
</p>
<blockquote class="templatequote"><p>It is incorrect to assume that
diseases appear one by one in humans. Disease infects by spreading from
one person to another. This infection occurs through seeds that are so
small they cannot be seen but are alive.</p></blockquote>
<p>In <a href="https://en.wikipedia.org/wiki/1546_in_science#Medicine" title="1546 in science">1546</a>, <a href="https://en.wikipedia.org/wiki/Girolamo_Fracastoro" title="Girolamo Fracastoro">Girolamo Fracastoro</a> proposed that <a href="https://en.wikipedia.org/wiki/Epidemic" title="Epidemic">epidemic</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Diseases" title="Diseases">diseases</a>
were caused by transferable seedlike entities that could transmit
infection by direct or indirect contact, or even without contact over
long distances.
</p><p><a href="https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek" title="Antonie van Leeuwenhoek">Antonie van Leeuwenhoek</a> is considered to be one of the <a href="https://en.wikipedia.org/wiki/List_of_people_considered_father_or_mother_of_a_scientific_field" title="List of people considered father or mother of a scientific field">fathers of microbiology</a>.
He was the first in 1673 to discover and conduct scientific experiments
with microorganisms, using simple single-lensed microscopes of his own
design. <a href="https://en.wikipedia.org/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a>, a contemporary of Leeuwenhoek, also used <a href="https://en.wikipedia.org/wiki/Microscopy" title="Microscopy">microscopy</a> to observe microbial life in the form of the fruiting bodies of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mold_(fungus)" title="Mold (fungus)">moulds</a>. In his <a href="https://en.wikipedia.org/wiki/1665#July–December" title="1665">1665</a> book <i><a href="https://en.wikipedia.org/wiki/Micrographia" title="Micrographia">Micrographia</a></i>, he made drawings of studies, and he coined the term <i><a href="https://en.wikipedia.org/wiki/Cell_(biology)" title="Cell (biology)">cell</a></i>.
</p>
<h3><span class="mw-headline" id="19th_century">19th century</span></h3><figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg"><img class="mw-file-element" data-file-height="2532" data-file-width="2082" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg/170px-Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg" width="329" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> showed that Spallanzani's findings held even if air could enter through a filter that kept particles out.</figcaption></figure>
<p><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a>
(1822–1895) exposed boiled broths to the air, in vessels that contained
a filter to prevent particles from passing through to the <a href="https://en.wikipedia.org/wiki/Growth_medium" title="Growth medium">growth medium</a>,
and also in vessels without a filter, but with air allowed in via a
curved tube so dust particles would settle and not come in contact with
the broth. By boiling the broth beforehand, Pasteur ensured that no
microorganisms survived within the broths at the beginning of his
experiment. Nothing grew in the broths in the course of Pasteur's
experiment. This meant that the living organisms that grew in such
broths came from outside, as <a href="https://en.wikipedia.org/wiki/Spore" title="Spore">spores</a> on dust, rather than spontaneously generated within the broth. Thus, Pasteur refuted the theory of <a href="https://en.wikipedia.org/wiki/Spontaneous_generation" title="Spontaneous generation">spontaneous generation</a> and supported the <a href="https://en.wikipedia.org/wiki/Germ_theory_of_disease" title="Germ theory of disease">germ theory of disease</a>.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Robert_Koch.jpg"><img class="mw-file-element" data-file-height="3124" data-file-width="2519" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Robert_Koch.jpg/170px-Robert_Koch.jpg" width="322" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Robert_Koch" title="Robert Koch">Robert Koch</a> showed that microorganisms caused <a href="https://en.wikipedia.org/wiki/Disease" title="Disease">disease</a>.</figcaption></figure>
<p>In 1876, <a href="https://en.wikipedia.org/wiki/Robert_Koch" title="Robert Koch">Robert Koch</a> (1843–1910) established that microorganisms can cause disease. He found that the blood of cattle that were infected with <a href="https://en.wikipedia.org/wiki/Anthrax" title="Anthrax">anthrax</a> always had large numbers of <i><a href="https://en.wikipedia.org/wiki/Bacillus_anthracis" title="Bacillus anthracis">Bacillus anthracis</a></i>.
Koch found that he could transmit anthrax from one animal to another by
taking a small sample of blood from the infected animal and injecting
it into a healthy one, and this caused the healthy animal to become
sick. He also found that he could grow the bacteria in a nutrient broth,
then inject it into a healthy animal, and cause illness. Based on these
experiments, he devised criteria for establishing a causal link between
a microorganism and a disease and these are now known as <a href="https://en.wikipedia.org/wiki/Koch%27s_postulates" title="Koch's postulates">Koch's postulates</a>.
Although these postulates cannot be applied in all cases, they do
retain historical importance to the development of scientific thought
and are still being used today.
</p><p>The discovery of microorganisms such as <i><a href="https://en.wikipedia.org/wiki/Euglena" title="Euglena">Euglena</a></i> that did not fit into either the <a href="https://en.wikipedia.org/wiki/Animal" title="Animal">animal</a> or <a href="https://en.wikipedia.org/wiki/Plant" title="Plant">plant</a> kingdoms, since they were <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Photosynthetic" title="Photosynthetic">photosynthetic</a> like plants, but <a href="https://en.wikipedia.org/wiki/Motility" title="Motility">motile</a> like animals, led to the naming of a third kingdom in the 1860s. In 1860 <a href="https://en.wikipedia.org/wiki/John_Hogg_(biologist)" title="John Hogg (biologist)">John Hogg</a> called this the Protoctista, and in 1866 <a href="https://en.wikipedia.org/wiki/Ernst_Haeckel" title="Ernst Haeckel">Ernst Haeckel</a> named it the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Protista" title="Protista">Protista</a>.
</p><p>The work of Pasteur and Koch did not accurately reflect the true
diversity of the microbial world because of their exclusive focus on
microorganisms having direct medical relevance. It was not until the
work of <a href="https://en.wikipedia.org/wiki/Martinus_Beijerinck" title="Martinus Beijerinck">Martinus Beijerinck</a> and <a href="https://en.wikipedia.org/wiki/Sergei_Winogradsky" title="Sergei Winogradsky">Sergei Winogradsky</a> late in the nineteenth century that the true breadth of microbiology was revealed. Beijerinck made two major contributions to microbiology: the discovery of <a href="https://en.wikipedia.org/wiki/Virus" title="Virus">viruses</a> and the development of <a href="https://en.wikipedia.org/wiki/Enrichment_culture" title="Enrichment culture">enrichment culture</a> techniques. While his work on the <a href="https://en.wikipedia.org/wiki/Tobacco_mosaic_virus" title="Tobacco mosaic virus">tobacco mosaic virus</a>
established the basic principles of virology, it was his development of
enrichment culturing that had the most immediate impact on microbiology
by allowing for the cultivation of a wide range of microbes with wildly
different physiologies. Winogradsky was the first to develop the
concept of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chemolithotrophy" title="Chemolithotrophy">chemolithotrophy</a> and to thereby reveal the essential role played by microorganisms in geochemical processes. He was responsible for the first isolation and description of both <a href="https://en.wikipedia.org/wiki/Nitrifying_bacteria" title="Nitrifying bacteria">nitrifying</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Nitrogen-fixing_bacteria" title="Nitrogen-fixing bacteria">nitrogen-fixing bacteria</a>. French-Canadian microbiologist <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Felix_d%27Herelle" title="Felix d'Herelle">Felix d'Herelle</a> co-discovered <a href="https://en.wikipedia.org/wiki/Bacteriophage" title="Bacteriophage">bacteriophages</a> and was one of the earliest applied microbiologists.
</p>
<h2><span class="mw-headline" id="Classification_and_structure">Classification and structure</span></h2><p>Microorganisms can be found almost anywhere on <a href="https://en.wikipedia.org/wiki/Earth" title="Earth">Earth</a>. <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">Bacteria</a> and <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">archaea</a> are almost always microscopic, while a number of <a href="https://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote">eukaryotes</a> are also microscopic, including most <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Protista" title="Protista">protists</a>, some <a href="https://en.wikipedia.org/wiki/Fungus" title="Fungus">fungi</a>, as well as some <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Micro-animal" title="Micro-animal">micro-animals</a> and plants. <a href="https://en.wikipedia.org/wiki/Virus" title="Virus">Viruses</a> are generally regarded as <a href="https://en.wikipedia.org/wiki/Non-cellular_life" title="Non-cellular life">not living</a> and therefore not considered to be microorganisms, although a subfield of <a href="https://en.wikipedia.org/wiki/Microbiology" title="Microbiology">microbiology</a> is <a href="https://en.wikipedia.org/wiki/Virology" title="Virology">virology</a>, the study of viruses.
</p>
<h3><span class="mw-headline" id="Evolution">Evolution</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life" title="Timeline of the evolutionary history of life">Timeline of the evolutionary history of life</a> and <a href="https://en.wikipedia.org/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></div>
<figure class="mw-halign-right noresize"><span><img class="mw-file-element" data-file-height="1010" data-file-width="1860" height="217" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Phylogenetic_tree.svg/325px-Phylogenetic_tree.svg.png" usemap="#ImageMap_2874f636ecfb8a34" width="400" /></span><a class="mw-file-magnify" href="https://en.wikipedia.org/wiki/File:Phylogenetic_tree.svg"></a><map name="ImageMap_2874f636ecfb8a34"><area alt="Bacteria" coords="43,1,91,13" href="https://en.wikipedia.org/wiki/Bacteria" shape="rect" title="Bacteria"></area><area alt="Archaea" coords="142,1,190,13" href="https://en.wikipedia.org/wiki/Archaea" shape="rect" title="Archaea"></area><area alt="Eukaryota" coords="226,1,283,13" href="https://en.wikipedia.org/wiki/Eukaryota" shape="rect" title="Eukaryota"></area><area alt="Aquifex" coords="5,135,31,144" href="https://en.wikipedia.org/wiki/Aquificota" shape="rect" title="Aquifex"></area><area alt="Thermotoga" coords="5,121,43,130" href="https://en.wikipedia.org/wiki/Thermotogota" shape="rect" title="Thermotoga"></area><area alt="Bacteroides–Cytophaga" coords="3,100,43,116" href="https://en.wikipedia.org/wiki/Bacteroidota" shape="rect" title="Bacteroides–Cytophaga"></area><area alt="Planctomyces" coords="2,82,49,90" href="https://en.wikipedia.org/wiki/Planctomycetota" shape="rect" title="Planctomyces"></area><area alt=""Cyanobacteria"" coords="6,72,53,79" href="https://en.wikipedia.org/wiki/Cyanobacteria" shape="rect" title=""Cyanobacteria""></area><area alt="Proteobacteria" coords="30,59,77,68" href="https://en.wikipedia.org/wiki/Pseudomonadota" shape="rect" title="Proteobacteria"></area><area alt="Spirochetes" coords="43,35,82,43" href="https://en.wikipedia.org/wiki/Spirochaetota" shape="rect" title="Spirochetes"></area><area alt="Gram-positives" coords="82,46,113,61" href="https://en.wikipedia.org/wiki/Gram-positive_bacteria" shape="rect" title="Gram-positives"></area><area alt="Chloroflexi" coords="113,34,150,43" href="https://en.wikipedia.org/wiki/Chloroflexota" shape="rect" title="Chloroflexi"></area><area alt="Thermoproteus–Pyrodictium" coords="112,85,163,100" href="https://en.wikipedia.org/wiki/Thermoproteota" shape="rect" title="Thermoproteus–Pyrodictium"></area><area alt="Thermococcus celer" coords="120,72,167,85" href="https://en.wikipedia.org/wiki/Thermococcus_celer" shape="rect" title="Thermococcus celer"></area><area alt="Methanococcus" coords="123,63,179,72" href="https://en.wikipedia.org/wiki/Methanococcus" shape="rect" title="Methanococcus"></area><area alt="Methanobacterium" coords="120,54,194,63" href="https://en.wikipedia.org/wiki/Methanobacterium" shape="rect" title="Methanobacterium"></area><area alt="Methanosarcina" coords="143,45,193,54" href="https://en.wikipedia.org/wiki/Methanosarcina" shape="rect" title="Methanosarcina"></area><area alt="Haloarchaea" coords="189,55,230,64" href="https://en.wikipedia.org/wiki/Halobacteria" shape="rect" title="Haloarchaea"></area><area alt="Entamoebae" coords="182,34,225,43" href="https://en.wikipedia.org/wiki/Entamoebae" shape="rect" title="Entamoebae"></area><area alt="Slime molds" coords="233,32,255,47" href="https://en.wikipedia.org/wiki/Slime_mold" shape="rect" title="Slime molds"></area><area alt="Animals" coords="265,35,294,43" href="https://en.wikipedia.org/wiki/Animal" shape="rect" title="Animals"></area><area alt="Fungi" coords="275,45,296,53" href="https://en.wikipedia.org/wiki/Fungus" shape="rect" title="Fungi"></area><area alt="Plants" coords="275,60,297,68" href="https://en.wikipedia.org/wiki/Plant" shape="rect" title="Plants"></area><area alt="Ciliates" coords="275,70,300,79" href="https://en.wikipedia.org/wiki/Ciliate" shape="rect" title="Ciliates"></area><area alt="Flagellates" coords="274,86,309,95" href="https://en.wikipedia.org/wiki/Flagellate" shape="rect" title="Flagellates"></area><area alt="Trichomonads" coords="272,100,319,109" href="https://en.wikipedia.org/wiki/Trichomonad" shape="rect" title="Trichomonads"></area><area alt="Microsporidia" coords="270,117,316,125" href="https://en.wikipedia.org/wiki/Microsporidia" shape="rect" title="Microsporidia"></area><area alt="Diplomonads" coords="268,132,312,141" href="https://en.wikipedia.org/wiki/Diplomonad" shape="rect" title="Diplomonads"></area></map><figcaption><a href="https://en.wikipedia.org/wiki/Carl_Woese" title="Carl Woese">Carl Woese</a>'s 1990 <a href="https://en.wikipedia.org/wiki/Phylogenetic_tree" title="Phylogenetic tree">phylogenetic tree</a> based on <a class="mw-redirect" href="https://en.wikipedia.org/wiki/RRNA" title="RRNA">rRNA</a> data shows the domains of <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">Bacteria</a>, <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">Archaea</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eukaryota" title="Eukaryota">Eukaryota</a>. All are microorganisms except some eukaryote groups.</figcaption></figure>
<p>Single-celled microorganisms were the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Origin_of_life" title="Origin of life">first forms of life</a> to develop on Earth, approximately 3.5 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gigaannum" title="Gigaannum">billion years</a> ago. Further evolution was slow, and for about 3 billion years in the <a href="https://en.wikipedia.org/wiki/Precambrian" title="Precambrian">Precambrian</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eon_(geology)" title="Eon (geology)">eon</a>, (much of the history of <a href="https://en.wikipedia.org/wiki/Life" title="Life">life on Earth</a>), all <a href="https://en.wikipedia.org/wiki/Organism" title="Organism">organisms</a> were microorganisms. Bacteria, algae and fungi have been identified in <a href="https://en.wikipedia.org/wiki/Amber" title="Amber">amber</a> that is 220 million years old, which shows that the <a href="https://en.wikipedia.org/wiki/Morphology_(biology)" title="Morphology (biology)">morphology</a> of microorganisms has changed little since at least the <a href="https://en.wikipedia.org/wiki/Triassic" title="Triassic">Triassic</a> period. The newly discovered <a href="https://en.wikipedia.org/wiki/Nickel#Biological_role" title="Nickel">biological role played by nickel</a>, however – especially that brought about by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Types_of_volcanic_eruption" title="Types of volcanic eruption">volcanic eruptions</a> from the <a href="https://en.wikipedia.org/wiki/Siberian_Traps" title="Siberian Traps">Siberian Traps</a> – may have accelerated the evolution of <a href="https://en.wikipedia.org/wiki/Methanogen" title="Methanogen">methanogens</a> towards the end of the <a href="https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event" title="Permian–Triassic extinction event">Permian–Triassic extinction event</a>.
</p><p>Microorganisms tend to have a relatively fast rate of evolution.
Most microorganisms can reproduce rapidly, and bacteria are also able to
freely exchange genes through <a href="https://en.wikipedia.org/wiki/Bacterial_conjugation" title="Bacterial conjugation">conjugation</a>, <a href="https://en.wikipedia.org/wiki/Transformation_(genetics)" title="Transformation (genetics)">transformation</a> and <a href="https://en.wikipedia.org/wiki/Transduction_(genetics)" title="Transduction (genetics)">transduction</a>, even between widely divergent species. This <a href="https://en.wikipedia.org/wiki/Horizontal_gene_transfer" title="Horizontal gene transfer">horizontal gene transfer</a>, coupled with a high <a href="https://en.wikipedia.org/wiki/Mutation" title="Mutation">mutation</a> rate and other means of transformation, allows microorganisms to swiftly <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Biological_evolution" title="Biological evolution">evolve</a> (via <a href="https://en.wikipedia.org/wiki/Natural_selection" title="Natural selection">natural selection</a>) to survive in new environments and respond to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Stressors" title="Stressors">environmental stresses</a>. This rapid evolution is important in medicine, as it has led to the development of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Multidrug_resistance" title="Multidrug resistance">multidrug resistant</a> <a href="https://en.wikipedia.org/wiki/Pathogenic_bacteria" title="Pathogenic bacteria">pathogenic bacteria</a>, <i>superbugs</i>, that are <a href="https://en.wikipedia.org/wiki/Antimicrobial_resistance" title="Antimicrobial resistance">resistant to antibiotics</a>.
</p><p>A possible transitional form of microorganism between a
prokaryote and a eukaryote was discovered in 2012 by Japanese
scientists. <i><a href="https://en.wikipedia.org/wiki/Parakaryon_myojinensis" title="Parakaryon myojinensis">Parakaryon myojinensis</a></i>
is a unique microorganism larger than a typical prokaryote, but with
nuclear material enclosed in a membrane as in a eukaryote, and the
presence of endosymbionts. This is seen to be the first plausible
evolutionary form of microorganism, showing a stage of development from
the prokaryote to the eukaryote.
</p>
<h3><span class="mw-headline" id="Archaea">Archaea</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">Archaea</a></div>
<div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Prokaryote" title="Prokaryote">Prokaryote</a></div>
<p>Archaea are <a href="https://en.wikipedia.org/wiki/Prokaryote" title="Prokaryote">prokaryotic</a> unicellular organisms, and form the first domain of life in <a href="https://en.wikipedia.org/wiki/Carl_Woese" title="Carl Woese">Carl Woese</a>'s <a href="https://en.wikipedia.org/wiki/Three-domain_system" title="Three-domain system">three-domain system</a>. A prokaryote is defined as having no <a href="https://en.wikipedia.org/wiki/Cell_nucleus" title="Cell nucleus">cell nucleus</a> or other <a href="https://en.wikipedia.org/wiki/Lipid_bilayer" title="Lipid bilayer">membrane bound</a>-<a href="https://en.wikipedia.org/wiki/Organelle" title="Organelle">organelle</a>.
Archaea share this defining feature with the bacteria with which they
were once grouped. In 1990 the microbiologist Woese proposed the
three-domain system that divided living things into bacteria, archaea
and eukaryotes, and thereby split the prokaryote domain.
</p><p>Archaea differ from bacteria in both their genetics and biochemistry. For example, while bacterial <a href="https://en.wikipedia.org/wiki/Cell_membrane" title="Cell membrane">cell membranes</a> are made from <a href="https://en.wikipedia.org/wiki/Phospholipid" title="Phospholipid">phosphoglycerides</a> with <a href="https://en.wikipedia.org/wiki/Ester" title="Ester">ester</a> bonds, archaean membranes are made of <a href="https://en.wikipedia.org/wiki/Ether_lipid" title="Ether lipid">ether lipids</a>. Archaea were originally described as <a href="https://en.wikipedia.org/wiki/Extremophile" title="Extremophile">extremophiles</a> living in <a href="https://en.wikipedia.org/wiki/Extreme_environment" title="Extreme environment">extreme environments</a>, such as <a href="https://en.wikipedia.org/wiki/Hot_spring" title="Hot spring">hot springs</a>, but have since been found in all types of <a href="https://en.wikipedia.org/wiki/Habitat" title="Habitat">habitats</a>. Only now are scientists beginning to realize how common archaea are in the environment, with <a href="https://en.wikipedia.org/wiki/Thermoproteota" title="Thermoproteota">Thermoproteota</a>
(formerly Crenarchaeota) being the most common form of life in the
ocean, dominating ecosystems below 150 metres (490 ft) in depth.<sup class="reference" id="cite_ref-46"><a href="https://en.wikipedia.org/wiki/Microorganism#cite_note-46">[45]</a></sup><sup class="reference" id="cite_ref-47"><a href="https://en.wikipedia.org/wiki/Microorganism#cite_note-47">[46]</a></sup> These organisms are also common in soil and play a vital role in <a href="https://en.wikipedia.org/wiki/Ammonia" title="Ammonia">ammonia</a> oxidation.
</p><p>The combined domains of archaea and bacteria make up the most diverse and abundant group of <a href="https://en.wikipedia.org/wiki/Organism" title="Organism">organisms</a> on Earth and inhabit practically all environments where the temperature is below +140 °C (284 °F). They are found in <a href="https://en.wikipedia.org/wiki/Water" title="Water">water</a>, <a href="https://en.wikipedia.org/wiki/Soil" title="Soil">soil</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Earth%27s_atmosphere" title="Earth's atmosphere">air</a>, as the <a href="https://en.wikipedia.org/wiki/Microbiome" title="Microbiome">microbiome</a> of an organism, <a href="https://en.wikipedia.org/wiki/Hot_spring" title="Hot spring">hot springs</a> and even deep beneath the Earth's crust in <a href="https://en.wikipedia.org/wiki/Rock_(geology)" title="Rock (geology)">rocks</a>. The number of prokaryotes is estimated to be around five nonillion, or 5 × 10<sup>30</sup>, accounting for at least half the <a href="https://en.wikipedia.org/wiki/Biomass_(ecology)" title="Biomass (ecology)">biomass</a> on Earth.
</p><p>The biodiversity of the prokaryotes is unknown, but may be very
large. A May 2016 estimate, based on laws of scaling from known numbers
of species against the size of organism, gives an estimate of perhaps
1 trillion species on the planet, of which most would be microorganisms.
Currently, only one-thousandth of one percent of that total have been
described. <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">Archael cells</a> of some species aggregate and transfer <a href="https://en.wikipedia.org/wiki/DNA" title="DNA">DNA</a> from one cell to another through direct contact, particularly under stressful environmental conditions that cause <a href="https://en.wikipedia.org/wiki/DNA_damage_(naturally_occurring)" title="DNA damage (naturally occurring)">DNA damage</a>.
</p>
<h3><span class="mw-headline" id="Bacteria">Bacteria</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">Bacteria</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Staphylococcus_aureus_01.jpg"><img class="mw-file-element" data-file-height="1630" data-file-width="2100" height="311" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Staphylococcus_aureus_01.jpg/220px-Staphylococcus_aureus_01.jpg" width="400" /></a><figcaption><i><a href="https://en.wikipedia.org/wiki/Staphylococcus_aureus" title="Staphylococcus aureus">Staphylococcus aureus</a></i> bacteria magnified about 10,000x</figcaption></figure>
<p>Like archaea, bacteria are prokaryotic – unicellular, and having no
cell nucleus or other membrane-bound organelle. Bacteria are
microscopic, with a few extremely rare exceptions, such as <i><a href="https://en.wikipedia.org/wiki/Thiomargarita_namibiensis" title="Thiomargarita namibiensis">Thiomargarita namibiensis</a></i>. Bacteria function and reproduce as individual cells, but they can often aggregate in multicellular <a href="https://en.wikipedia.org/wiki/Colony_(biology)#Microbial_colony" title="Colony (biology)">colonies</a>. Some species such as <a href="https://en.wikipedia.org/wiki/Myxobacteria" title="Myxobacteria">myxobacteria</a> can aggregate into complex <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Swarm" title="Swarm">swarming</a> structures, operating as multicellular groups as part of their <a href="https://en.wikipedia.org/wiki/Biological_life_cycle" title="Biological life cycle">life cycle</a>, or form clusters in <a href="https://en.wikipedia.org/wiki/Colony_(biology)" title="Colony (biology)">bacterial colonies</a> such as <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/E.coli" title="E.coli">E.coli</a></i>.
</p><p>Their <a href="https://en.wikipedia.org/wiki/Genome" title="Genome">genome</a> is usually a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Circular_bacterial_chromosome" title="Circular bacterial chromosome">circular bacterial chromosome</a> – a single loop of <a href="https://en.wikipedia.org/wiki/DNA" title="DNA">DNA</a>, although they can also harbor small pieces of DNA called <a href="https://en.wikipedia.org/wiki/Plasmid" title="Plasmid">plasmids</a>. These plasmids can be transferred between cells through <a href="https://en.wikipedia.org/wiki/Bacterial_conjugation" title="Bacterial conjugation">bacterial conjugation</a>. Bacteria have an enclosing <a href="https://en.wikipedia.org/wiki/Bacterial_cell_structure#Cell_wall" title="Bacterial cell structure">cell wall</a>, which provides strength and rigidity to their cells. They reproduce by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Binary_fission" title="Binary fission">binary fission</a> or sometimes by <a href="https://en.wikipedia.org/wiki/Budding" title="Budding">budding</a>, but do not undergo <a href="https://en.wikipedia.org/wiki/Meiosis" title="Meiosis">meiotic</a> <a href="https://en.wikipedia.org/wiki/Sexual_reproduction" title="Sexual reproduction">sexual reproduction</a>. However, many bacterial species can transfer DNA between individual cells by a <a href="https://en.wikipedia.org/wiki/Horizontal_gene_transfer" title="Horizontal gene transfer">horizontal gene transfer</a> process referred to as natural <a href="https://en.wikipedia.org/wiki/Transformation_(genetics)" title="Transformation (genetics)">transformation</a>. Some species form extraordinarily resilient <a href="https://en.wikipedia.org/wiki/Endospore" title="Endospore">spores</a>,
but for bacteria this is a mechanism for survival, not reproduction.
Under optimal conditions bacteria can grow extremely rapidly and their
numbers can double as quickly as every 20 minutes.
</p>
<h3><span class="mw-headline" id="Eukaryotes">Eukaryotes</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote">Eukaryote</a></div>
<p>Most living things that are visible to the naked eye in their adult form are <a href="https://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote">eukaryotes</a>, including <a href="https://en.wikipedia.org/wiki/Human" title="Human">humans</a>. However, many eukaryotes are also microorganisms. Unlike <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">bacteria</a> and <a href="https://en.wikipedia.org/wiki/Archaea" title="Archaea">archaea</a>, eukaryotes contain <a href="https://en.wikipedia.org/wiki/Organelle" title="Organelle">organelles</a> such as the <a href="https://en.wikipedia.org/wiki/Cell_nucleus" title="Cell nucleus">cell nucleus</a>, the <a href="https://en.wikipedia.org/wiki/Golgi_apparatus" title="Golgi apparatus">Golgi apparatus</a> and <a href="https://en.wikipedia.org/wiki/Mitochondrion" title="Mitochondrion">mitochondria</a> in their <a href="https://en.wikipedia.org/wiki/Cell_(biology)" title="Cell (biology)">cells</a>. The nucleus is an organelle that houses the <a href="https://en.wikipedia.org/wiki/DNA" title="DNA">DNA</a> that makes up a cell's genome. DNA (Deoxyribonucleic acid) itself is arranged in complex <a href="https://en.wikipedia.org/wiki/Chromosome" title="Chromosome">chromosomes</a>.
Mitochondria are organelles vital in <a href="https://en.wikipedia.org/wiki/Metabolism" title="Metabolism">metabolism</a> as they are the site of the <a href="https://en.wikipedia.org/wiki/Citric_acid_cycle" title="Citric acid cycle">citric acid cycle</a> and <a href="https://en.wikipedia.org/wiki/Oxidative_phosphorylation" title="Oxidative phosphorylation">oxidative phosphorylation</a>. They evolved from <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Symbiotic" title="Symbiotic">symbiotic</a> bacteria and retain a remnant genome. Like bacteria, <a href="https://en.wikipedia.org/wiki/Plant_cell" title="Plant cell">plant cells</a> have <a href="https://en.wikipedia.org/wiki/Cell_wall" title="Cell wall">cell walls</a>, and contain organelles such as <a href="https://en.wikipedia.org/wiki/Chloroplast" title="Chloroplast">chloroplasts</a> in addition to the organelles in other eukaryotes. Chloroplasts produce energy from <a href="https://en.wikipedia.org/wiki/Light" title="Light">light</a> by <a href="https://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a>, and were also originally symbiotic <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">bacteria</a>.
</p><p>Unicellular eukaryotes consist of a single <a href="https://en.wikipedia.org/wiki/Cell_(biology)" title="Cell (biology)">cell</a> throughout their life cycle. This qualification is significant since most <a href="https://en.wikipedia.org/wiki/Multicellular_organism" title="Multicellular organism">multicellular</a> eukaryotes consist of a single cell called a <a href="https://en.wikipedia.org/wiki/Zygote" title="Zygote">zygote</a> only at the beginning of their life cycles. Microbial eukaryotes can be either <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Haploid" title="Haploid">haploid</a> or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Diploid" title="Diploid">diploid</a>, and some organisms have multiple <a href="https://en.wikipedia.org/wiki/Cell_nucleus" title="Cell nucleus">cell nuclei</a>.
</p><p>Unicellular eukaryotes usually reproduce asexually by <a href="https://en.wikipedia.org/wiki/Mitosis" title="Mitosis">mitosis</a>
under favorable conditions. However, under stressful conditions such as
nutrient limitations and other conditions associated with DNA damage,
they tend to reproduce sexually by <a href="https://en.wikipedia.org/wiki/Meiosis" title="Meiosis">meiosis</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fertilization" title="Fertilization">syngamy</a>.
</p>
<h4><span class="mw-headline" id="Protists">Protists</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Protista" title="Protista">Protista</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Euglena_mutabilis_-_400x_-_1_(10388739803)_(cropped).jpg"><img class="mw-file-element" data-file-height="669" data-file-width="667" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Euglena_mutabilis_-_400x_-_1_%2810388739803%29_%28cropped%29.jpg/170px-Euglena_mutabilis_-_400x_-_1_%2810388739803%29_%28cropped%29.jpg" width="398" /></a><figcaption><i><a href="https://en.wikipedia.org/wiki/Euglena" title="Euglena">Euglena mutabilis</a></i>, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Photosynthetic" title="Photosynthetic">photosynthetic</a> <a href="https://en.wikipedia.org/wiki/Flagellate" title="Flagellate">flagellate</a></figcaption></figure>
<p>Of <a href="https://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote">eukaryotic</a> groups, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Protists" title="Protists">protists</a> are most commonly <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Unicellular" title="Unicellular">unicellular</a> and microscopic. This is a highly diverse group of organisms that are not easy to classify. Several <a href="https://en.wikipedia.org/wiki/Algae" title="Algae">algae</a> <a href="https://en.wikipedia.org/wiki/Species" title="Species">species</a> are <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Multicellular" title="Multicellular">multicellular</a> protists, and <a href="https://en.wikipedia.org/wiki/Slime_mold" title="Slime mold">slime molds</a> have unique life cycles that involve switching between unicellular, colonial, and multicellular forms.
The number of species of protists is unknown since only a small
proportion has been identified. Protist diversity is high in oceans,
deep sea-vents, river sediment and an acidic river, suggesting that many
eukaryotic microbial communities may yet be discovered.
</p>
<h4><span class="mw-headline" id="Fungi">Fungi</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Fungus" title="Fungus">Fungus</a></div>
<p>The <a href="https://en.wikipedia.org/wiki/Fungus" title="Fungus">fungi</a> have several unicellular species, such as baker's yeast (<i><a href="https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae" title="Saccharomyces cerevisiae">Saccharomyces cerevisiae</a></i>) and fission yeast (<i><a href="https://en.wikipedia.org/wiki/Schizosaccharomyces_pombe" title="Schizosaccharomyces pombe">Schizosaccharomyces pombe</a></i>). Some fungi, such as the pathogenic yeast <i><a href="https://en.wikipedia.org/wiki/Candida_albicans" title="Candida albicans">Candida albicans</a></i>, can undergo <a href="https://en.wikipedia.org/wiki/Phenotypic_switching" title="Phenotypic switching">phenotypic switching</a> and grow as single cells in some environments, and <a href="https://en.wikipedia.org/wiki/Hypha" title="Hypha">filamentous hyphae</a> in others.
</p>
<h4><span class="mw-headline" id="Plants">Plants</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Plant" title="Plant">Plant</a></div>
<p>The <a href="https://en.wikipedia.org/wiki/Green_algae" title="Green algae">green algae</a>
are a large group of photosynthetic eukaryotes that include many
microscopic organisms. Although some green algae are classified as <a href="https://en.wikipedia.org/wiki/Protist" title="Protist">protists</a>, others such as <a href="https://en.wikipedia.org/wiki/Charophyta" title="Charophyta">charophyta</a> are classified with <a href="https://en.wikipedia.org/wiki/Embryophyte" title="Embryophyte">embryophyte</a>
plants, which are the most familiar group of land plants. Algae can
grow as single cells, or in long chains of cells. The green algae
include unicellular and colonial <a href="https://en.wikipedia.org/wiki/Flagellate" title="Flagellate">flagellates</a>, usually but not always with two <a href="https://en.wikipedia.org/wiki/Flagellum" title="Flagellum">flagella</a> per cell, as well as various colonial, <a href="https://en.wikipedia.org/wiki/Chlorococcales" title="Chlorococcales">coccoid</a>, and filamentous forms. In the <a href="https://en.wikipedia.org/wiki/Charales" title="Charales">Charales</a>,
which are the algae most closely related to higher plants, cells
differentiate into several distinct tissues within the organism. There
are about 6000 species of green algae.
</p>
<h2><span class="mw-headline" id="Ecology">Ecology</span></h2><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Microbial_ecology" title="Microbial ecology">Microbial ecology</a></div>
<p>Microorganisms are found in almost every <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Habitat_(ecology)" title="Habitat (ecology)">habitat</a> present in nature, including hostile environments such as the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Geographic_poles" title="Geographic poles">North and South poles</a>, <a href="https://en.wikipedia.org/wiki/Desert" title="Desert">deserts</a>, <a href="https://en.wikipedia.org/wiki/Geyser" title="Geyser">geysers</a>, and <a href="https://en.wikipedia.org/wiki/Rock_(geology)" title="Rock (geology)">rocks</a>. They also include all the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marine_microorganism" title="Marine microorganism">marine microorganisms</a> of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/World_ocean" title="World ocean">oceans</a> and <a href="https://en.wikipedia.org/wiki/Deep_sea" title="Deep sea">deep sea</a>. Some types of microorganisms have adapted to <a href="https://en.wikipedia.org/wiki/Extreme_environment" title="Extreme environment">extreme environments</a> and sustained colonies; these organisms are known as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Extremophiles" title="Extremophiles">extremophiles</a>. Extremophiles have been isolated from rocks as much as 7 kilometres below the Earth's surface,
and it has been suggested that the amount of organisms living below the
Earth's surface is comparable with the amount of life on or above the
surface. Extremophiles have been known to survive for a prolonged time in a <a href="https://en.wikipedia.org/wiki/Vacuum" title="Vacuum">vacuum</a>, and can be highly resistant to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ultraviolet_radiation" title="Ultraviolet radiation">radiation</a>, which may even allow them to survive in space. Many types of microorganisms have intimate <a href="https://en.wikipedia.org/wiki/Symbiosis" title="Symbiosis">symbiotic relationships</a> with other larger organisms; some of which are mutually beneficial (<a href="https://en.wikipedia.org/wiki/Mutualism_(biology)" title="Mutualism (biology)">mutualism</a>), while others can be damaging to the <a href="https://en.wikipedia.org/wiki/Host_(biology)" title="Host (biology)">host</a> organism (<a href="https://en.wikipedia.org/wiki/Parasitism" title="Parasitism">parasitism</a>). If microorganisms can cause <a href="https://en.wikipedia.org/wiki/Disease" title="Disease">disease</a> in a host they are known as <a href="https://en.wikipedia.org/wiki/Pathogen" title="Pathogen">pathogens</a> and then they are sometimes referred to as <i>microbes</i>.
Microorganisms play critical roles in Earth's <a href="https://en.wikipedia.org/wiki/Biogeochemical_cycle" title="Biogeochemical cycle">biogeochemical cycles</a> as they are responsible for <a href="https://en.wikipedia.org/wiki/Decomposition" title="Decomposition">decomposition</a> and <a href="https://en.wikipedia.org/wiki/Nitrogen_fixation" title="Nitrogen fixation">nitrogen fixation</a>.
</p><p>Bacteria use <a href="https://en.wikipedia.org/wiki/Gene_regulatory_network" title="Gene regulatory network">regulatory networks</a> that allow them to adapt to almost every environmental niche on earth.
A network of interactions among diverse types of molecules including
DNA, RNA, proteins and metabolites, is utilised by the bacteria to
achieve <a href="https://en.wikipedia.org/wiki/Regulation_of_gene_expression" title="Regulation of gene expression">regulation of gene expression</a>.
In bacteria, the principal function of regulatory networks is to
control the response to environmental changes, for example nutritional
status and environmental stress. A complex organization of networks permits the microorganism to coordinate and integrate multiple environmental signals.
</p>
<h3><span class="mw-headline" id="Extremophiles">Extremophiles</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Extremophile" title="Extremophile">Extremophile</a></div>
<div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/List_of_microorganisms_tested_in_outer_space" title="List of microorganisms tested in outer space">List of microorganisms tested in outer space</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Deinococcus_radiodurans.jpg"><img class="mw-file-element" data-file-height="612" data-file-width="532" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Deinococcus_radiodurans.jpg/170px-Deinococcus_radiodurans.jpg" width="347" /></a><figcaption>A tetrad of <i><a href="https://en.wikipedia.org/wiki/Deinococcus_radiodurans" title="Deinococcus radiodurans">Deinococcus radiodurans</a></i>, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Radioresistant" title="Radioresistant">radioresistant</a> <a href="https://en.wikipedia.org/wiki/Extremophile" title="Extremophile">extremophile</a> bacterium</figcaption></figure>
<p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Extremophiles" title="Extremophiles">Extremophiles</a> are microorganisms that have adapted so that they can survive and even thrive in <a href="https://en.wikipedia.org/wiki/Extreme_environment" title="Extreme environment">extreme environments</a> that are normally fatal to most life-forms. <a href="https://en.wikipedia.org/wiki/Thermophile" title="Thermophile">Thermophiles</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hyperthermophiles" title="Hyperthermophiles">hyperthermophiles</a> thrive in high <a href="https://en.wikipedia.org/wiki/Temperature" title="Temperature">temperatures</a>. <a href="https://en.wikipedia.org/wiki/Psychrophile" title="Psychrophile">Psychrophiles</a> thrive in extremely low temperatures. – Temperatures as high as 130 °C (266 °F), as low as −17 °C (1 °F) <a href="https://en.wikipedia.org/wiki/Halophile" title="Halophile">Halophiles</a> such as <i><a href="https://en.wikipedia.org/wiki/Halobacterium_salinarum" title="Halobacterium salinarum">Halobacterium salinarum</a></i> (an archaean) thrive in high <a href="https://en.wikipedia.org/wiki/Salinity" title="Salinity">salt conditions</a>, up to saturation. <a href="https://en.wikipedia.org/wiki/Alkaliphile" title="Alkaliphile">Alkaliphiles</a> thrive in an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alkaline" title="Alkaline">alkaline</a> <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> of about 8.5–11. <a href="https://en.wikipedia.org/wiki/Acidophile" title="Acidophile">Acidophiles</a> can thrive in a pH of 2.0 or less. <a href="https://en.wikipedia.org/wiki/Piezophile" title="Piezophile">Piezophiles</a> thrive at very <a href="https://en.wikipedia.org/wiki/High_pressure" title="High pressure">high pressures</a>: up to 1,000–2,000 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Atmosphere_(unit)" title="Atmosphere (unit)">atm</a>, down to 0 atm as in a <a href="https://en.wikipedia.org/wiki/Vacuum" title="Vacuum">vacuum</a> of <a href="https://en.wikipedia.org/wiki/Outer_space" title="Outer space">space</a>. A few extremophiles such as <i><a href="https://en.wikipedia.org/wiki/Deinococcus_radiodurans" title="Deinococcus radiodurans">Deinococcus radiodurans</a></i> are <a href="https://en.wikipedia.org/wiki/Radioresistance" title="Radioresistance">radioresistant</a>, resisting <a href="https://en.wikipedia.org/wiki/Ionizing_radiation" title="Ionizing radiation">radiation</a> exposure of up to 5k <a href="https://en.wikipedia.org/wiki/Gray_(unit)" title="Gray (unit)">Gy</a>. Extremophiles are significant in different ways. They extend terrestrial life into much of the Earth's <a href="https://en.wikipedia.org/wiki/Hydrosphere" title="Hydrosphere">hydrosphere</a>, <a href="https://en.wikipedia.org/wiki/Crust_(geology)" title="Crust (geology)">crust</a> and <a href="https://en.wikipedia.org/wiki/Atmosphere" title="Atmosphere">atmosphere</a>, their specific evolutionary adaptation mechanisms to their extreme environment can be exploited in <a href="https://en.wikipedia.org/wiki/Biotechnology" title="Biotechnology">biotechnology</a>, and their very existence under such extreme conditions increases the potential for <a href="https://en.wikipedia.org/wiki/Extraterrestrial_life" title="Extraterrestrial life">extraterrestrial life</a>.
</p>
<h3><span class="mw-headline" id="Plants_and_soil">Plants and soil</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Soil_biology" title="Soil biology">Soil biology</a></div>
<p>The <a href="https://en.wikipedia.org/wiki/Nitrogen_cycle" title="Nitrogen cycle">nitrogen cycle</a> in soils depends on the <a href="https://en.wikipedia.org/wiki/Nitrogen_fixation" title="Nitrogen fixation">fixation of atmospheric nitrogen</a>. This is achieved by a number of <a href="https://en.wikipedia.org/wiki/Diazotroph" title="Diazotroph">diazotrophs</a>. One way this can occur is in the <a href="https://en.wikipedia.org/wiki/Root_nodule" title="Root nodule">root nodules</a> of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Legumes" title="Legumes">legumes</a> that contain symbiotic <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">bacteria</a> of the genera <i><a href="https://en.wikipedia.org/wiki/Rhizobium" title="Rhizobium">Rhizobium</a></i>, <i><a href="https://en.wikipedia.org/wiki/Mesorhizobium" title="Mesorhizobium">Mesorhizobium</a></i>, <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sinorhizobium" title="Sinorhizobium">Sinorhizobium</a></i>, <i><a href="https://en.wikipedia.org/wiki/Bradyrhizobium" title="Bradyrhizobium">Bradyrhizobium</a></i>, and <i><a href="https://en.wikipedia.org/wiki/Azorhizobium" title="Azorhizobium">Azorhizobium</a></i>.
</p><p>The <a href="https://en.wikipedia.org/wiki/Root" title="Root">roots</a> of plants create a narrow region known as the <a href="https://en.wikipedia.org/wiki/Rhizosphere" title="Rhizosphere">rhizosphere</a> that supports many microorganisms known as the <a href="https://en.wikipedia.org/wiki/Root_microbiome" title="Root microbiome">root microbiome</a>.
</p><p>These microorganisms in the <a href="https://en.wikipedia.org/wiki/Root_microbiome" title="Root microbiome">root microbiome</a> are able to interact with each other and surrounding plants through signals and cues. For example, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mycorrhizal_fungi" title="Mycorrhizal fungi">mycorrhizal fungi</a> are able to communicate with the root systems of many plants through chemical signals between both the <a href="https://en.wikipedia.org/wiki/Plant" title="Plant">plant</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fungi" title="Fungi">fungi</a>. This results in a mutualistic <a href="https://en.wikipedia.org/wiki/Symbiosis" title="Symbiosis">symbiosis</a> between the two. However, these signals can be eavesdropped by other microorganisms, such as the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Soil_bacteria" title="Soil bacteria">soil bacteria</a>, <i>Myxococcus xanthus</i>,
which preys on other bacteria. Eavesdropping, or the interception of
signals from unintended receivers, such as plants and microorganisms,
can lead to large-scale, evolutionary consequences. For example,
signaler-receiver pairs, like plant-microorganism pairs, may lose the
ability to communicate with neighboring populations because of
variability in eavesdroppers. In adapting to avoid local eavesdroppers,
signal divergence could occur and thus, lead to the isolation of plants
and microorganisms from the inability to communicate with other
populations.
</p>
<h3><span class="mw-headline" id="Symbiosis">Symbiosis</span></h3><figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Hyella_caespitosa.jpg"><img class="mw-file-element" data-file-height="1680" data-file-width="2240" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Hyella_caespitosa.jpg/220px-Hyella_caespitosa.jpg" width="400" /></a><figcaption>The photosynthetic <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cyanobacterium" title="Cyanobacterium">cyanobacterium</a> <i>Hyella caespitosa</i> (round shapes) with fungal hyphae (translucent threads) in the <a href="https://en.wikipedia.org/wiki/Lichen" title="Lichen">lichen</a> <i>Pyrenocollema halodytes</i></figcaption></figure>
<p>A <a href="https://en.wikipedia.org/wiki/Lichen" title="Lichen">lichen</a> is a <a href="https://en.wikipedia.org/wiki/Symbiosis" title="Symbiosis">symbiosis</a> of a macroscopic fungus with <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Photosynthetic" title="Photosynthetic">photosynthetic</a> microbial <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alga" title="Alga">algae</a> or <a href="https://en.wikipedia.org/wiki/Cyanobacteria" title="Cyanobacteria">cyanobacteria</a>.<sup> </sup></p><p><sup> </sup><span class="mw-headline" id="Applications">Applications</span></p><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Human_interactions_with_microbes" title="Human interactions with microbes">Human interactions with microbes</a></div>
<p>Microorganisms are useful in producing foods, treating waste water,
creating biofuels and a wide range of chemicals and enzymes. They are
invaluable in research as <a href="https://en.wikipedia.org/wiki/Model_organism" title="Model organism">model organisms</a>. They have been <a href="https://en.wikipedia.org/wiki/Biological_agent" title="Biological agent">weaponised</a> and sometimes used in <a href="https://en.wikipedia.org/wiki/Biological_warfare" title="Biological warfare">warfare</a> and <a href="https://en.wikipedia.org/wiki/Bioterrorism" title="Bioterrorism">bioterrorism</a>. They are vital to agriculture through their roles in maintaining <a href="https://en.wikipedia.org/wiki/Soil_fertility" title="Soil fertility">soil fertility</a> and in decomposing organic matter.
</p>
<h3><span class="mw-headline" id="Food_production">Food production</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Fermentation_in_food_processing" title="Fermentation in food processing">Fermentation in food processing</a> and <a href="https://en.wikipedia.org/wiki/Food_microbiology" title="Food microbiology">Food microbiology</a></div>
<p>Microorganisms are used in a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fermentation_(food)" title="Fermentation (food)">fermentation</a> process to make <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Yoghurt" title="Yoghurt">yoghurt</a>, <a href="https://en.wikipedia.org/wiki/Cheese" title="Cheese">cheese</a>, <a href="https://en.wikipedia.org/wiki/Curd" title="Curd">curd</a>, <a href="https://en.wikipedia.org/wiki/Kefir" title="Kefir">kefir</a>, <a href="https://en.wikipedia.org/wiki/Ayran" title="Ayran">ayran</a>, <a href="https://en.wikipedia.org/wiki/Fermented_milk_products" title="Fermented milk products">xynogala</a>, and other types of food. Fermentation cultures provide flavour and aroma, and inhibit undesirable organisms. They are used to <a href="https://en.wikipedia.org/wiki/Leavening_agent" title="Leavening agent">leaven</a> <a href="https://en.wikipedia.org/wiki/Bread" title="Bread">bread</a>, and to convert <a href="https://en.wikipedia.org/wiki/Sugar" title="Sugar">sugars</a> to <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">alcohol</a> in <a href="https://en.wikipedia.org/wiki/Wine" title="Wine">wine</a> and <a href="https://en.wikipedia.org/wiki/Beer" title="Beer">beer</a>. Microorganisms are used in <a href="https://en.wikipedia.org/wiki/Brewing" title="Brewing">brewing</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Wine_making" title="Wine making">wine making</a>, <a href="https://en.wikipedia.org/wiki/Baking" title="Baking">baking</a>, <a href="https://en.wikipedia.org/wiki/Pickling" title="Pickling">pickling</a> and other <a href="https://en.wikipedia.org/wiki/Food" title="Food">food</a>-making processes.
</p>
<table class="wikitable plainrowheaders">
<caption>Example industrial uses of microorganisms
</caption>
<tbody><tr>
<th scope="col">Product
</th>
<th scope="col">Contribution of microorganisms
</th></tr>
<tr>
<th scope="row">Cheese
</th>
<td>Growth of microorganisms contributes to ripening and flavor. The
flavor and appearance of a particular cheese is due in large part to the
microorganisms associated with it. <i><a href="https://en.wikipedia.org/wiki/Lactobacillus_bulgaricus_GLB44" title="Lactobacillus bulgaricus GLB44">Lactobacillus Bulgaricus</a></i> is one of the microbes used in production of <a href="https://en.wikipedia.org/wiki/Dairy_product" title="Dairy product">dairy products</a>
</td></tr>
<tr>
<th scope="row">Alcoholic beverages
</th>
<td>yeast is used to convert sugar, grape juice, or malt-treated grain
into alcohol. other microorganisms may also be used; a mold converts
starch into sugar to make the Japanese rice wine, sake. <i><a href="https://en.wikipedia.org/wiki/Acetobacter_aceti" title="Acetobacter aceti">Acetobacter Aceti</a></i> a kind of bacterium is used in production of Alcoholic beverages
</td></tr>
<tr>
<th scope="row">Vinegar
</th>
<td>Certain bacteria are used to convert alcohol into acetic acid, which gives vinegar its acid taste. <i><a href="https://en.wikipedia.org/wiki/Acetobacter_aceti" title="Acetobacter aceti">Acetobacter Aceti</a></i> is used on production of vinegar, which gives vinegar odor of alcohol and alcoholic taste
</td></tr>
<tr>
<th scope="row">Citric acid
</th>
<td>Certain fungi are used to make citric acid, a common ingredient of soft drinks and other foods.
</td></tr>
<tr>
<th scope="row">Vitamins
</th>
<td>Microorganisms are used to make vitamins, including C, B<sub>2</sub> , B<sub>12.</sub>
</td></tr>
<tr>
<th scope="row">Antibiotics
</th>
<td>With only a few exceptions, microorganisms are used to make antibiotics. <i><a href="https://en.wikipedia.org/wiki/Penicillin" title="Penicillin">Penicillin</a>, <a href="https://en.wikipedia.org/wiki/Amoxicillin" title="Amoxicillin">Amoxicillin</a>, <a href="https://en.wikipedia.org/wiki/Tetracycline" title="Tetracycline">Tetracycline</a>, and <a href="https://en.wikipedia.org/wiki/Erythromycin" title="Erythromycin">Erythromycin</a></i>
</td></tr></tbody></table>
<h3><span class="mw-headline" id="Water_treatment">Water treatment</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Drinking_water#Water_quality" title="Drinking water">Drinking water § Water quality</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:WWTP_Antwerpen-Zuid.jpg"><img class="mw-file-element" data-file-height="2085" data-file-width="2810" height="296" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/WWTP_Antwerpen-Zuid.jpg/220px-WWTP_Antwerpen-Zuid.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Wastewater_treatment" title="Wastewater treatment">Wastewater treatment plants</a> rely largely on microorganisms to oxidise organic matter.</figcaption></figure>
<p>These depend for their ability to clean up water contaminated with
organic material on microorganisms that can respire dissolved
substances. Respiration may be aerobic, with a well-oxygenated filter
bed such as a <a href="https://en.wikipedia.org/wiki/Slow_sand_filter" title="Slow sand filter">slow sand filter</a>. <a href="https://en.wikipedia.org/wiki/Anaerobic_digestion" title="Anaerobic digestion">Anaerobic digestion</a> by <a href="https://en.wikipedia.org/wiki/Methanogen" title="Methanogen">methanogens</a> generate useful <a href="https://en.wikipedia.org/wiki/Methane" title="Methane">methane</a> gas as a by-product.
</p>
<h3><span class="mw-headline" id="Energy">Energy</span></h3><p>Microorganisms are used in <a href="https://en.wikipedia.org/wiki/Ethanol_fermentation" title="Ethanol fermentation">fermentation to produce ethanol</a>, and in <a href="https://en.wikipedia.org/wiki/Biogas" title="Biogas">biogas</a> reactors to produce <a href="https://en.wikipedia.org/wiki/Methane" title="Methane">methane</a>. Scientists are researching the use of <a href="https://en.wikipedia.org/wiki/Algae_fuel" title="Algae fuel">algae to produce liquid fuels</a>, and bacteria to convert various forms of agricultural and urban waste into <a href="https://en.wikipedia.org/wiki/Cellulosic_ethanol" title="Cellulosic ethanol">usable fuels</a>.
</p>
<h3><span id="Chemicals.2C_enzymes"></span><span class="mw-headline" id="Chemicals,_enzymes">Chemicals, enzymes</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Synthesis_of_nanoparticles_by_fungi" title="Synthesis of nanoparticles by fungi">Synthesis of nanoparticles by fungi</a></div>
<p>Microorganisms are used to produce many commercial and industrial chemicals, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Enzymes" title="Enzymes">enzymes</a> and other bioactive molecules. Organic acids produced on a large industrial scale by microbial fermentation include <a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">acetic acid</a> produced by <a href="https://en.wikipedia.org/wiki/Acetic_acid_bacteria" title="Acetic acid bacteria">acetic acid bacteria</a> such as <i><a href="https://en.wikipedia.org/wiki/Acetobacter_aceti" title="Acetobacter aceti">Acetobacter aceti</a></i>, <a href="https://en.wikipedia.org/wiki/Butyric_acid" title="Butyric acid">butyric acid</a> made by the bacterium <i><a href="https://en.wikipedia.org/wiki/Clostridium_butyricum" title="Clostridium butyricum">Clostridium butyricum</a></i>, <a href="https://en.wikipedia.org/wiki/Lactic_acid" title="Lactic acid">lactic acid</a> made by <i><a href="https://en.wikipedia.org/wiki/Lactobacillus" title="Lactobacillus">Lactobacillus</a></i> and other <a href="https://en.wikipedia.org/wiki/Lactic_acid_bacteria" title="Lactic acid bacteria">lactic acid bacteria</a>, and <a href="https://en.wikipedia.org/wiki/Citric_acid" title="Citric acid">citric acid</a> produced by the mould fungus <i><a href="https://en.wikipedia.org/wiki/Aspergillus_niger" title="Aspergillus niger">Aspergillus niger</a></i>.
</p><p>Microorganisms are used to prepare bioactive molecules such as <a href="https://en.wikipedia.org/wiki/Streptokinase" title="Streptokinase">Streptokinase</a> from the bacterium <i><a href="https://en.wikipedia.org/wiki/Streptococcus" title="Streptococcus">Streptococcus</a></i>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cyclosporin_A" title="Cyclosporin A">Cyclosporin A</a> from the ascomycete fungus <i><a href="https://en.wikipedia.org/wiki/Tolypocladium_inflatum" title="Tolypocladium inflatum">Tolypocladium inflatum</a></i>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Statins" title="Statins">statins</a> produced by the yeast <i><a href="https://en.wikipedia.org/wiki/Monascus_purpureus" title="Monascus purpureus">Monascus purpureus</a></i>.
</p>
<h3><span class="mw-headline" id="Science">Science</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Genetically_modified_bacteria" title="Genetically modified bacteria">Genetically modified bacteria</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Biofermentor.jpeg"><img class="mw-file-element" data-file-height="2448" data-file-width="3264" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/ca/Biofermentor.jpeg/220px-Biofermentor.jpeg" width="400" /></a><figcaption>A laboratory <a href="https://en.wikipedia.org/wiki/Fermentation" title="Fermentation">fermentation</a> vessel</figcaption></figure>
<p>Microorganisms are essential tools in <a href="https://en.wikipedia.org/wiki/Biotechnology" title="Biotechnology">biotechnology</a>, <a href="https://en.wikipedia.org/wiki/Biochemistry" title="Biochemistry">biochemistry</a>, <a href="https://en.wikipedia.org/wiki/Genetics" title="Genetics">genetics</a>, and <a href="https://en.wikipedia.org/wiki/Molecular_biology" title="Molecular biology">molecular biology</a>. The <a href="https://en.wikipedia.org/wiki/Yeast" title="Yeast">yeasts</a> <i><a href="https://en.wikipedia.org/wiki/Saccharomyces_cerevisiae" title="Saccharomyces cerevisiae">Saccharomyces cerevisiae</a></i> and <i><a href="https://en.wikipedia.org/wiki/Schizosaccharomyces_pombe" title="Schizosaccharomyces pombe">Schizosaccharomyces pombe</a></i> are important <a href="https://en.wikipedia.org/wiki/Model_organism" title="Model organism">model organisms</a> in science, since they are simple eukaryotes that can be grown rapidly in large numbers and are easily manipulated. They are particularly valuable in <a href="https://en.wikipedia.org/wiki/Genetics" title="Genetics">genetics</a>, <a href="https://en.wikipedia.org/wiki/Genomics" title="Genomics">genomics</a> and <a href="https://en.wikipedia.org/wiki/Proteomics" title="Proteomics">proteomics</a>.
Microorganisms can be harnessed for uses such as creating steroids and
treating skin diseases. Scientists are also considering using
microorganisms for living <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fuel_cells" title="Fuel cells">fuel cells</a>, and as a solution for pollution.
</p>
<h3><span class="mw-headline" id="Warfare">Warfare</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Biological_warfare" title="Biological warfare">Biological warfare</a> and <a href="https://en.wikipedia.org/wiki/Bioterrorism" title="Bioterrorism">Bioterrorism</a></div>
<p>In the <a href="https://en.wikipedia.org/wiki/Middle_Ages" title="Middle Ages">Middle Ages</a>, as an early example of <a href="https://en.wikipedia.org/wiki/Biological_warfare" title="Biological warfare">biological warfare</a>, diseased corpses were thrown into castles during <a href="https://en.wikipedia.org/wiki/Siege" title="Siege">sieges</a> using catapults or other <a href="https://en.wikipedia.org/wiki/Siege_engine" title="Siege engine">siege engines</a>. Individuals near the corpses were exposed to the pathogen and were likely to spread that pathogen to others.
</p><p>In modern times, <a href="https://en.wikipedia.org/wiki/Bioterrorism" title="Bioterrorism">bioterrorism</a> has included the <a href="https://en.wikipedia.org/wiki/1984_Rajneeshee_bioterror_attack" title="1984 Rajneeshee bioterror attack">1984 Rajneeshee bioterror attack</a> and the 1993 release of <a href="https://en.wikipedia.org/wiki/Anthrax" title="Anthrax">anthrax</a> by <a href="https://en.wikipedia.org/wiki/Aum_Shinrikyo" title="Aum Shinrikyo">Aum Shinrikyo</a> in Tokyo.
</p>
<h3><span class="mw-headline" id="Soil">Soil</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Soil_microbiology" title="Soil microbiology">Soil microbiology</a></div><p>Microbes can make <a href="https://en.wikipedia.org/wiki/Nutrient" title="Nutrient">nutrients</a> and minerals in the soil available to plants, produce <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hormones" title="Hormones">hormones</a> that spur growth, stimulate the plant <a href="https://en.wikipedia.org/wiki/Immune_system" title="Immune system">immune system</a> and trigger or dampen stress responses. In general a more diverse set of <a href="https://en.wikipedia.org/wiki/Soil_biology" title="Soil biology">soil</a> microbes results in fewer plant diseases and higher yield.
</p><h2><span class="mw-headline" id="Human_health">Human health</span></h2><h3><span class="mw-headline" id="Human_gut_flora">Human gut flora</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Human_microbiota" title="Human microbiota">Human microbiota</a> and <a href="https://en.wikipedia.org/wiki/Human_Microbiome_Project" title="Human Microbiome Project">Human Microbiome Project</a></div>
<p>Microorganisms can form an <a href="https://en.wikipedia.org/wiki/Endosymbiont" title="Endosymbiont">endosymbiotic</a> relationship with other, larger organisms. For example, <a href="https://en.wikipedia.org/wiki/Microbial_symbiosis_and_immunity" title="Microbial symbiosis and immunity">microbial symbiosis</a> plays a crucial role in the immune system. The microorganisms that make up the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gut_flora" title="Gut flora">gut flora</a> in the <a href="https://en.wikipedia.org/wiki/Gastrointestinal_tract" title="Gastrointestinal tract">gastrointestinal tract</a> contribute to gut immunity, synthesize <a href="https://en.wikipedia.org/wiki/Vitamin" title="Vitamin">vitamins</a> such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Folic_acid" title="Folic acid">folic acid</a> and <a href="https://en.wikipedia.org/wiki/Biotin" title="Biotin">biotin</a>, and ferment complex indigestible <a href="https://en.wikipedia.org/wiki/Carbohydrate" title="Carbohydrate">carbohydrates</a>. Some microorganisms that are seen to be beneficial to health are termed <a href="https://en.wikipedia.org/wiki/Probiotic" title="Probiotic">probiotics</a> and are available as <a href="https://en.wikipedia.org/wiki/Dietary_supplement" title="Dietary supplement">dietary supplements</a>, or <a href="https://en.wikipedia.org/wiki/Food_additive#Fortifying_agents" title="Food additive">food additives</a>.
</p>
<h3><span class="mw-headline" id="Disease">Disease</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Pathogen" title="Pathogen">Pathogen</a> and <a href="https://en.wikipedia.org/wiki/Germ_theory_of_disease" title="Germ theory of disease">Germ theory of disease</a></div>
<div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Medical_microbiology" title="Medical microbiology">Medical microbiology</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Parasite" title="Parasite">Parasite</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Plasmodium.jpg"><img class="mw-file-element" data-file-height="473" data-file-width="440" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Plasmodium.jpg/170px-Plasmodium.jpg" width="372" /></a><figcaption>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eukaryotic" title="Eukaryotic">eukaryotic</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Parasite" title="Parasite">parasite</a> <i><a href="https://en.wikipedia.org/wiki/Plasmodium_falciparum" title="Plasmodium falciparum">Plasmodium falciparum</a></i> (spiky blue shapes), a causative agent of <a href="https://en.wikipedia.org/wiki/Malaria" title="Malaria">malaria</a>, in human <a href="https://en.wikipedia.org/wiki/Blood" title="Blood">blood</a></figcaption></figure>
<p>Microorganisms are the causative agents (<a href="https://en.wikipedia.org/wiki/Pathogen" title="Pathogen">pathogens</a>) in many <a href="https://en.wikipedia.org/wiki/Infection" title="Infection">infectious diseases</a>. The organisms involved include <a href="https://en.wikipedia.org/wiki/Pathogenic_bacteria" title="Pathogenic bacteria">pathogenic bacteria</a>, causing diseases such as <a href="https://en.wikipedia.org/wiki/Bubonic_plague" title="Bubonic plague">plague</a>, <a href="https://en.wikipedia.org/wiki/Tuberculosis" title="Tuberculosis">tuberculosis</a> and <a href="https://en.wikipedia.org/wiki/Anthrax" title="Anthrax">anthrax</a>; <a href="https://en.wikipedia.org/wiki/Protozoa" title="Protozoa">protozoan</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Parasite" title="Parasite">parasites</a>, causing diseases such as <a href="https://en.wikipedia.org/wiki/Malaria" title="Malaria">malaria</a>, <a href="https://en.wikipedia.org/wiki/African_trypanosomiasis" title="African trypanosomiasis">sleeping sickness</a>, <a href="https://en.wikipedia.org/wiki/Dysentery" title="Dysentery">dysentery</a> and <a href="https://en.wikipedia.org/wiki/Toxoplasmosis" title="Toxoplasmosis">toxoplasmosis</a>; and also fungi causing diseases such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ringworm" title="Ringworm">ringworm</a>, <a href="https://en.wikipedia.org/wiki/Candidiasis" title="Candidiasis">candidiasis</a> or <a href="https://en.wikipedia.org/wiki/Histoplasmosis" title="Histoplasmosis">histoplasmosis</a>. However, other diseases such as <a href="https://en.wikipedia.org/wiki/Influenza" title="Influenza">influenza</a>, <a href="https://en.wikipedia.org/wiki/Yellow_fever" title="Yellow fever">yellow fever</a> or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/AIDS" title="AIDS">AIDS</a> are caused by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pathogenic_viruses" title="Pathogenic viruses">pathogenic viruses</a>,
which are not usually classified as living organisms and are not,
therefore, microorganisms by the strict definition. No clear examples of
archaean pathogens are known, although a relationship has been proposed between the presence of some archaean methanogens and human <a href="https://en.wikipedia.org/wiki/Periodontal_disease" title="Periodontal disease">periodontal disease</a>. Numerous microbial pathogens are capable of sexual processes that appear to facilitate their survival in their infected host.
</p>
<h3><span class="mw-headline" id="Hygiene">Hygiene</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Hygiene" title="Hygiene">Hygiene</a> and <a href="https://en.wikipedia.org/wiki/Food_microbiology" title="Food microbiology">Food microbiology</a></div>
<p>Hygiene is a set of practices to avoid <a href="https://en.wikipedia.org/wiki/Infection" title="Infection">infection</a> or <a href="https://en.wikipedia.org/wiki/Food_spoilage" title="Food spoilage">food spoilage</a> by eliminating microorganisms from the surroundings. As microorganisms, in particular <a href="https://en.wikipedia.org/wiki/Bacteria" title="Bacteria">bacteria</a>, are found virtually everywhere, <a href="https://en.wikipedia.org/wiki/Pathogen" title="Pathogen">harmful microorganisms</a> may be reduced to acceptable levels rather than actually eliminated. In food preparation, microorganisms are reduced by <a href="https://en.wikipedia.org/wiki/Food_preservation" title="Food preservation">preservation</a>
methods such as cooking, cleanliness of utensils, short storage
periods, or by low temperatures. If complete sterility is needed, as
with surgical equipment, an <a href="https://en.wikipedia.org/wiki/Autoclave" title="Autoclave">autoclave</a> is used to kill microorganisms with heat and pressure.
</p>
<h2><span class="mw-headline" id="In_fiction">In fiction</span></h2><ul><li><i><a href="https://en.wikipedia.org/wiki/Osmosis_Jones" title="Osmosis Jones">Osmosis Jones</a></i>, a 2001 film, and its show <i><a href="https://en.wikipedia.org/wiki/Ozzy_%26_Drix" title="Ozzy & Drix">Ozzy & Drix</a></i>, set in a stylized version of the human body, featured anthropomorphic microorganisms.</li><li><i><a href="https://en.wikipedia.org/wiki/War_of_the_Worlds_(2005_film)" title="War of the Worlds (2005 film)">War of the Worlds (2005 film)</a></i>, when Alien lifeforms attempt to conquer earth, they are ultimately defeated by a common Microbe to which Humans are immune.</li></ul>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-75745690325210113702024-03-18T13:52:00.004-04:002024-03-18T13:52:53.168-04:00Magnocellular cell<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
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<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell">https://en.wikipedia.org/wiki/Magnocellular_cell</a><br /><h2><span class="mw-headline" id="Structure">Structure</span></h2></div></div></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lateral_geniculate_nucleus.png"><img class="mw-file-element" data-file-height="259" data-file-width="300" height="190" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Lateral_geniculate_nucleus.png/220px-Lateral_geniculate_nucleus.png" width="220" /></a><figcaption>Schematic diagram of the primate LGN.</figcaption></figure>
<p>The full details of the flow of signaling from the eye to the visual cortex of the brain that result in the experience of <a href="https://en.wikipedia.org/wiki/Visual_perception" title="Visual perception">vision</a> are incompletely understood. Many aspects are subject to active controversy and the disruption of new evidence.
</p><p>In the <a href="https://en.wikipedia.org/wiki/Visual_system" title="Visual system">visual system</a>, signals mostly travel from the <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">retina</a> to the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a> (LGN) and then to the <a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">visual cortex</a>.
In humans the LGN is normally described as having six distinctive
layers. The inner two layers, (1 and 2) are magnocellular cell (M cell)
layers, while the outer four layers, (3,4,5 and 6), are <a href="https://en.wikipedia.org/wiki/Parvocellular_cell" title="Parvocellular cell">parvocellular cell</a> (P cell) layers. An additional set of neurons, known as the <a href="https://en.wikipedia.org/wiki/Koniocellular_cell" title="Koniocellular cell">koniocellular cell</a> (K cell) layers, are found ventral to each of the M cell and P cell layers. These layers were named this way because cells in the M layers of the LGN are larger than cells in the P layers.
</p><p>M cells in the LGN receive input from <a href="https://en.wikipedia.org/wiki/Parasol_cell" title="Parasol cell">parasol ganglion cells</a> (which some neuroscientists call M cells),<sup class="reference" id="cite_ref-Brodal2010_3-2"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell#cite_note-Brodal2010-3">[3]</a></sup><sup class="reference nowrap"><span title="Page / location: 226">: 226 </span></sup> and P cells receive input from <a href="https://en.wikipedia.org/wiki/Midget_cell" title="Midget cell">midget retinal ganglion cells</a> (which some neuroscientists call P cells).<sup class="reference" id="cite_ref-Brodal2010_3-3"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell#cite_note-Brodal2010-3">[3]</a></sup><sup class="reference nowrap"><span title="Page / location: 226">: 226 </span></sup><sup class="reference" id="cite_ref-Callaway2005_6-0"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell#cite_note-Callaway2005-6">[6]</a></sup><sup class="reference" id="cite_ref-Nassi2009_7-0"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell#cite_note-Nassi2009-7">[7]</a></sup>
</p>
<figure class="mw-halign-none"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Magno_Parvocellular_Pathways.svg"><img class="mw-file-element" data-file-height="322" data-file-width="553" height="233" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/Magno_Parvocellular_Pathways.svg/400px-Magno_Parvocellular_Pathways.svg.png" width="400" /></a><figcaption>Visual representation of the parvocellular and magnocellular pathways</figcaption></figure>
<p>From the LGN, the M pathway continues by sending information to the <a href="https://en.wikipedia.org/wiki/Blob_(visual_system)" title="Blob (visual system)">interblob</a> regions of the 4Cα layer of the <a href="https://en.wikipedia.org/wiki/Visual_cortex#Primary_visual_cortex" title="Visual cortex">V1</a> region of the visual cortex, also called the "striate cortex".
Other cells in the striate are more influenced from signaling from P
cells and yet others from K cells. As signals are passed to other
regions of the cortex, the signals start to be less separate, more
integrated, and more influenced by signals from other parts of the
brain. While classically it is said that signaling through the M
pathway ultimately flow out of the visual cortex through the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dorsal_stream" title="Dorsal stream">dorsal stream</a> and signaling through the P pathway ultimately flows to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ventral_stream" title="Ventral stream">ventral stream</a>, subsequent studies have shown that both pathways influence both streams.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Human_visual_pathway.svg"><img class="mw-file-element" data-file-height="341" data-file-width="449" height="304" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Human_visual_pathway.svg/300px-Human_visual_pathway.svg.png" width="400" /></a><figcaption>Human visual pathway</figcaption></figure>
<h2><span class="mw-headline" id="Function">Function</span></h2><p>The
magnocellular pathway cannot provide finely detailed or colored
information, but still provides useful static, depth, and motion
information. The M pathway has high light/dark contrast detection, and is more sensitive at low <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Spatial_frequencies" title="Spatial frequencies">spatial frequencies</a> than high spatial frequencies. Due to this contrast information, M cells are essential for detecting changes in <a href="https://en.wikipedia.org/wiki/Luminance" title="Luminance">luminance</a>, and performing <a href="https://en.wikipedia.org/wiki/Visual_search" title="Visual search">visual search</a> tasks and detecting edges.
</p><p>The M pathway is also important for providing information about
the location of objects. M cells can detect the orientation and position
of objects in space, information that is sent through the dorsal stream.
This information is also useful for detecting the difference in
positions of objects on the retina of each eye, an important tool in
binocular depth perception.
</p><p>Cells in the M pathway have the ability to detect high temporal
frequencies and can thus detect quick changes in the position of an
object. This is the basis for detecting motion. The information sent to the <a href="https://en.wikipedia.org/wiki/Intraparietal_sulcus" title="Intraparietal sulcus">intraparietal sulcus</a> (IPS) of the posterior parietal cortex allows the M pathway to direct attention and guide <a href="https://en.wikipedia.org/wiki/Saccade" title="Saccade">saccadic eye movements</a> to follow important moving objects in the visual field. In addition to following objects with the eyes, the IPS sends information to parts of the <a href="https://en.wikipedia.org/wiki/Frontal_lobe" title="Frontal lobe">frontal lobe</a>
that allows the hands and arms to adjust their movements to correctly
grasp objects based on their size, position, and location.
This ability has led some neuroscientists to hypothesize that the
purpose of the M pathway is not to detect spatial locations, but to
guide actions related to the position and motion of objects.
</p><p>Some information has also been found to support the hypothesis that the M pathway is necessary for <a href="https://en.wikipedia.org/wiki/Face_perception" title="Face perception">facial processing</a>.
</p>
<h2><span class="mw-headline" id="Clinical_significance">Clinical significance</span></h2><p>Abnormal
magnocellular pathways and magnocellular cells can be associated with
various disorders and ocular impairments, including dyslexia,
prosopagnosia and schizophrenia.
</p>
<h3><span class="mw-headline" id="Dyslexia">Dyslexia</span></h3><p><a href="https://en.wikipedia.org/wiki/Dyslexia" title="Dyslexia">Dyslexia</a>
is a disability which affects individual’s ability to read. It often
first manifests in childhood, if at all; however, dyslexia can manifest
itself in adulthood because of a brain tumor or lesion on/penetrating M
cells. There is no clear idea of the role of M cells and the magnocellular pathway in dyslexia.
</p><p>One theory suggests that the nonlinearity, size, and compensation
of miniature eye movements of M cells all help to focus on a single
target and blur the surroundings, which is crucial in reading. This
suggests that M cells are underdeveloped in many dyslexics. This may be
due to genetics, autoimmunity, or nutrition. The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/KIAA0319" title="KIAA0319">KIAA0319</a> gene on chromosome six controls <a href="https://en.wikipedia.org/wiki/Cell_migration" title="Cell migration">cell migration</a> to the LGN during development; and studies in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Transgenic_mice" title="Transgenic mice">transgenic mice</a>
and on brains of people with dyslexia examined after they died, show
malformations in the LGN and cells expressing KIAA0319 growing in the
wrong place.
M cells are vulnerable to antineuronal antibodies which attack and
render them unusable in the magnocellular pathway. This could be a cause
of why dyslexics are more likely to have weakened immune systems.
</p><p>Another line of research suggests that defective eye movement
caused by M cells is the cause of dyslexia. Since the magnocellular
system is sensitive to image movement, and dyslexia is posited to be
caused by abnormalities in M cells, dyslexics tend to focus on words
longer, take shorter scans when reading, and stop more often per line.
The study postulates that this is not caused by dyslexia but rather, low
comprehension of the text causing abnormal eye movements in M cells.
Therefore, it is difficult to conclude the importance of M cells in
dyslexia from this study.
</p>
<h3><span class="mw-headline" id="Schizophrenia">Schizophrenia</span></h3><a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">Schizophrenia</a>
is a mental disorder in which people are unable to differentiate what
is real and what is not. It is believed that the magnocellular pathway
may help with facial recognition and discrimination in children, but
when this pathway is not developed completely or correctly, facial
processing is more difficult for individuals later in life. This is seen
in people with schizophrenia and occurs when there are issues in the
integration of information from the M cell and P cell pathways, making
it difficult for individuals with schizophrenia to differentiate between
reality and hallucinations.<sup class="reference" id="cite_ref-Bortolon2015_19-2"><a href="https://en.wikipedia.org/wiki/Magnocellular_cell#cite_note-Bortolon2015-19"></a></sup>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-7754038535205650492024-03-18T09:03:00.000-04:002024-03-18T09:03:04.288-04:00Visual system<div class="vector-column-end">
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<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><a href="https://en.wikipedia.org/wiki/Visual_system">https://en.wikipedia.org/wiki/Visual_system</a></div><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"> <br /><table class="infobox"><tbody><tr><th class="infobox-above" colspan="2" style="background-color: dimgrey; color: white;">Visual system</th></tr><tr><td class="infobox-image" colspan="2"><span class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Human_visual_pathway.svg"><img class="mw-file-element" data-file-height="341" data-file-width="449" height="304" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Human_visual_pathway.svg/250px-Human_visual_pathway.svg.png" width="400" /></a></span><div class="infobox-caption">The
visual system includes the eyes, the connecting pathways through to the
visual cortex and other parts of the brain (human system shown).</div><div class="infobox-caption"> </div></td></tr><tr><td class="infobox-image" colspan="2"><span class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Human_eye_with_limbal_ring,_anterior_view.jpg"><img class="mw-file-element" data-file-height="675" data-file-width="1200" height="226" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/96/Human_eye_with_limbal_ring%2C_anterior_view.jpg/250px-Human_eye_with_limbal_ring%2C_anterior_view.jpg" width="400" /></a></span><div class="infobox-caption">The <a href="https://en.wikipedia.org/wiki/Eye" title="Eye">eye</a> is the sensory organ of the visual system. The <a href="https://en.wikipedia.org/wiki/Iris_(anatomy)" title="Iris (anatomy)">iris</a>, <a href="https://en.wikipedia.org/wiki/Pupil" title="Pupil">pupil</a>, and <a href="https://en.wikipedia.org/wiki/Sclera" title="Sclera">sclera</a> are visible</div></td></tr></tbody></table>
<p>The <b>visual system</b> is the physiological basis of <a href="https://en.wikipedia.org/wiki/Visual_perception" title="Visual perception">visual perception</a> (the ability to <a href="https://en.wikipedia.org/wiki/Perception" title="Perception">detect and process</a> <a href="https://en.wikipedia.org/wiki/Light" title="Light">light</a>). The system detects, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Phototransduction" title="Phototransduction">transduces</a> and interprets information concerning <a href="https://en.wikipedia.org/wiki/Light" title="Light">light</a> within the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Visible_range" title="Visible range">visible range</a> to construct an <a href="https://en.wikipedia.org/wiki/Imaging" title="Imaging">image</a> and build a <a href="https://en.wikipedia.org/wiki/Mental_model" title="Mental model">mental model</a> of the surrounding environment. The visual system is associated with the <a href="https://en.wikipedia.org/wiki/Eye" title="Eye">eye</a> and functionally divided into the <a href="https://en.wikipedia.org/wiki/Optics" title="Optics">optical</a> system (including <a href="https://en.wikipedia.org/wiki/Cornea" title="Cornea">cornea</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Crystalline_lens" title="Crystalline lens">lens</a>) and the <a href="https://en.wikipedia.org/wiki/Nervous_system" title="Nervous system">neural</a> system (including the <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">retina</a> and <a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">visual cortex</a>).
</p><p>The visual system performs a number of complex tasks based on the <i>image forming</i> functionality of the eye, including the formation of monocular images, the neural mechanisms underlying <a href="https://en.wikipedia.org/wiki/Stereopsis" title="Stereopsis">stereopsis</a> and assessment of distances to (<a href="https://en.wikipedia.org/wiki/Depth_perception" title="Depth perception">depth perception</a>) and between objects, <a href="https://en.wikipedia.org/wiki/Motion_perception" title="Motion perception">motion perception</a>, <a href="https://en.wikipedia.org/wiki/Pattern_recognition" title="Pattern recognition">pattern recognition</a>, accurate <a href="https://en.wikipedia.org/wiki/Motor_coordination" title="Motor coordination">motor coordination</a> under visual guidance, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Colour_vision" title="Colour vision">colour vision</a>. Together, these facilitate higher order tasks, such as <a href="https://en.wikipedia.org/wiki/Object_recognition_(cognitive_science)" title="Object recognition (cognitive science)">object identification</a>. The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Neuropsychological" title="Neuropsychological">neuropsychological</a> side of visual information processing is known as <a href="https://en.wikipedia.org/wiki/Visual_perception" title="Visual perception">visual perception</a>, an abnormality of which is called <a href="https://en.wikipedia.org/wiki/Visual_impairment" title="Visual impairment">visual impairment</a>, and a complete absence of which is called <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Blindness" title="Blindness">blindness</a>. The visual system also has several non-image forming visual functions, independent of visual perception, including the <a href="https://en.wikipedia.org/wiki/Pupillary_light_reflex" title="Pupillary light reflex">pupillary light reflex</a> and circadian <a href="https://en.wikipedia.org/wiki/Entrainment_(chronobiology)" title="Entrainment (chronobiology)">photoentrainment</a>.
</p><p>This article describes the human visual system, which is representative of <a href="https://en.wikipedia.org/wiki/Mammalian_vision" title="Mammalian vision">mammalian vision</a>, and to a lesser extent the <a href="https://en.wikipedia.org/wiki/Vertebrate" title="Vertebrate">vertebrate</a> visual system.
</p>
<h2><span class="mw-headline" id="System_overview">System overview</span></h2></div></div></div><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Comprehensive_List_of_Relevant_Pathways_for_the_Visual_System.png"><img class="mw-file-element" data-file-height="1333" data-file-width="732" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Comprehensive_List_of_Relevant_Pathways_for_the_Visual_System.png/220px-Comprehensive_List_of_Relevant_Pathways_for_the_Visual_System.png" width="219" /></a><figcaption>This
diagram linearly (unless otherwise mentioned) tracks the projections of
all known structures that allow for vision to their relevant endpoints
in the human brain. Click to enlarge the image.</figcaption><figcaption> </figcaption></figure>
<figure class="mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:ERP_-_optic_cabling.jpg"><img class="mw-file-element" data-file-height="600" data-file-width="800" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d0/ERP_-_optic_cabling.jpg/300px-ERP_-_optic_cabling.jpg" width="400" /></a><figcaption>Representation of optic pathways from each of the 4 quadrants of view for both eyes simultaneously</figcaption></figure>
<h3><span class="mw-headline" id="Optical">Optical</span></h3><p>Together, the <a href="https://en.wikipedia.org/wiki/Cornea" title="Cornea">cornea</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lens_(anatomy)" title="Lens (anatomy)">lens</a> refract light into a small image and shine it on the <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">retina</a>. The retina <a href="https://en.wikipedia.org/wiki/Visual_phototransduction" title="Visual phototransduction">transduces</a> this image into electrical pulses using <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rods_(eye)" title="Rods (eye)">rods</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cones_(eye)" title="Cones (eye)">cones</a>. The <a href="https://en.wikipedia.org/wiki/Optic_nerve" title="Optic nerve">optic nerve</a> then carries these pulses through the <a href="https://en.wikipedia.org/wiki/Optic_canal" title="Optic canal">optic canal</a>. Upon reaching the <a href="https://en.wikipedia.org/wiki/Optic_chiasm" title="Optic chiasm">optic chiasm</a> the nerve fibers decussate (left becomes right). The fibers then branch and terminate in three places.
</p>
<h3><span class="mw-headline" id="Neural">Neural</span></h3><p>Most of the optic nerve fibers end in the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a>
(LGN). Before the LGN forwards the pulses to V1 of the visual cortex
(primary) it gauges the range of objects and tags every major object
with a velocity tag. These tags predict object movement.
</p><p>The LGN also sends some fibers to V2 and V3.
</p><p>V1 performs edge-detection to understand spatial organization
(initially, 40 milliseconds in, focusing on even small spatial and color
changes. Then, 100 milliseconds in, upon receiving the translated LGN,
V2, and V3 info, also begins focusing on global organization). V1 also
creates a bottom-up <a href="https://en.wikipedia.org/wiki/Saliency_map" title="Saliency map">saliency map</a> to guide attention or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gaze_shift" title="Gaze shift">gaze shift</a>.
</p><p>V2 both forwards (direct and via <a href="https://en.wikipedia.org/wiki/Pulvinar_nuclei" title="Pulvinar nuclei">pulvinar</a>) pulses to V1 and receives them. Pulvinar is responsible for <a href="https://en.wikipedia.org/wiki/Saccade" title="Saccade">saccade</a> and visual attention. V2 serves much the same function as V1, however, it also handles <a href="https://en.wikipedia.org/wiki/Illusory_contours" title="Illusory contours">illusory contours</a>, determining depth by comparing left and right pulses (2D images), and foreground distinguishment. V2 connects to V1 - V5.
</p><p>V3 helps process '<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Global_motion" title="Global motion">global motion</a>' (direction and speed) of objects. V3 connects to V1 (weak), V2, and the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Inferior_temporal_cortex" title="Inferior temporal cortex">inferior temporal cortex</a>.
</p><p>V4 recognizes simple shapes, and gets input from V1 (strong), V2, V3, LGN, and pulvinar. V5's outputs include V4 and its surrounding area, and eye-movement motor cortices (<a href="https://en.wikipedia.org/wiki/Frontal_eye_fields" title="Frontal eye fields">frontal eye-field</a> and <a href="https://en.wikipedia.org/wiki/Lateral_intraparietal_cortex" title="Lateral intraparietal cortex">lateral intraparietal area</a>).
</p><p>V5's functionality is similar to that of the other V's, however,
it integrates local object motion into global motion on a complex level.
V6 works in conjunction with V5 on motion analysis. V5 analyzes
self-motion, whereas V6 analyzes motion of objects relative to the
background. V6's primary input is V1, with V5 additions. V6 houses the <a href="https://en.wikipedia.org/wiki/Topographic_map" title="Topographic map">topographical map</a>
for vision. V6 outputs to the region directly around it (V6A). V6A has
direct connections to arm-moving cortices, including the <a href="https://en.wikipedia.org/wiki/Premotor_cortex" title="Premotor cortex">premotor cortex</a>.
</p><p>The <a href="https://en.wikipedia.org/wiki/Inferior_temporal_gyrus" title="Inferior temporal gyrus">inferior temporal gyrus</a> recognizes complex shapes, objects, and faces or, in conjunction with the <a href="https://en.wikipedia.org/wiki/Hippocampus" title="Hippocampus">hippocampus</a>, creates new <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Memories" title="Memories">memories</a>. The <a href="https://en.wikipedia.org/wiki/Pretectal_area" title="Pretectal area">pretectal area</a> is seven unique <a href="https://en.wikipedia.org/wiki/Nucleus_(neuroanatomy)" title="Nucleus (neuroanatomy)">nuclei</a>. Anterior, posterior and medial pretectal nuclei inhibit pain (indirectly), aid in <a href="https://en.wikipedia.org/wiki/Rapid_eye_movement_sleep" title="Rapid eye movement sleep">REM</a>, and aid the <a href="https://en.wikipedia.org/wiki/Accommodation_reflex" title="Accommodation reflex">accommodation reflex</a>, respectively. The <a href="https://en.wikipedia.org/wiki/Edinger%E2%80%93Westphal_nucleus" title="Edinger–Westphal nucleus">Edinger-Westphal nucleus</a> moderates <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pupil_dilation" title="Pupil dilation">pupil dilation</a> and aids (since it provides parasympathetic fibers) in convergence of the eyes and lens adjustment. Nuclei of the optic tract are involved in smooth pursuit eye movement and the accommodation reflex, as well as REM.
</p><p>The <a href="https://en.wikipedia.org/wiki/Suprachiasmatic_nucleus" title="Suprachiasmatic nucleus">suprachiasmatic nucleus</a> is the region of the <a href="https://en.wikipedia.org/wiki/Hypothalamus" title="Hypothalamus">hypothalamus</a> that halts production of <a href="https://en.wikipedia.org/wiki/Melatonin" title="Melatonin">melatonin</a> (indirectly) at first light.
</p>
<h2><span class="mw-headline" id="Structure">Structure</span></h2><figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Schematic_diagram_of_the_human_eye_en.svg"><img class="mw-file-element" data-file-height="423" data-file-width="416" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Schematic_diagram_of_the_human_eye_en.svg/300px-Schematic_diagram_of_the_human_eye_en.svg.png" width="393" /></a><figcaption>The <a href="https://en.wikipedia.org/wiki/Human_eye" title="Human eye">human eye</a> (horizontal section)<br /><i>The image projected onto the retina is inverted due to the optics of the eye.</i></figcaption></figure>
<ul><li>The <a href="https://en.wikipedia.org/wiki/Eye#Eye" title="Eye">eye</a>, especially the <a href="https://en.wikipedia.org/wiki/Visual_system#Retina">retina</a></li><li>The <a href="https://en.wikipedia.org/wiki/Visual_system#Optic_nerve">optic nerve</a></li><li>The <a href="https://en.wikipedia.org/wiki/Optic_chiasm#Optic_chiasm" title="Optic chiasm">optic chiasma</a></li><li>The <a href="https://en.wikipedia.org/wiki/Visual_system#Optic_tract">optic tract</a></li><li>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lateral_geniculate_body#Lateral_geniculate_body" title="Lateral geniculate body">lateral geniculate body</a></li><li>The <a href="https://en.wikipedia.org/wiki/Optic_radiation#Optic_radiation" title="Optic radiation">optic radiation</a></li><li>The <a href="https://en.wikipedia.org/wiki/Visual_cortex#Visual_cortex" title="Visual cortex">visual cortex</a></li><li>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Visual_association_cortex#V2" title="Visual association cortex">visual association cortex</a>.</li></ul>
<p>These are components of the <b>visual pathway</b> also called the <b>optic pathway</b> that can be divided into <a href="https://en.wikipedia.org/wiki/Anatomical_terms_of_location#anterior" title="Anatomical terms of location">anterior and posterior visual pathways</a>. The anterior visual pathway refers to structures involved in vision before the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a>. The posterior visual pathway refers to structures after this point.
</p>
<h3><span class="mw-headline" id="Eye">Eye</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Eye" title="Eye">Eye</a> and <a href="https://en.wikipedia.org/wiki/Anterior_segment_of_eyeball" title="Anterior segment of eyeball">Anterior segment of eyeball</a></div>
<p>Light entering the eye is <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Refracted" title="Refracted">refracted</a> as it passes through the <a href="https://en.wikipedia.org/wiki/Cornea" title="Cornea">cornea</a>. It then passes through the <a href="https://en.wikipedia.org/wiki/Pupil" title="Pupil">pupil</a> (controlled by the <a href="https://en.wikipedia.org/wiki/Iris_(anatomy)" title="Iris (anatomy)">iris</a>) and is further refracted by the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lens_(vision)" title="Lens (vision)">lens</a>. The cornea and lens act together as a compound lens to project an inverted image onto the retina.
</p>
<figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Cajal_Retina.jpg"><img class="mw-file-element" data-file-height="745" data-file-width="500" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/Cajal_Retina.jpg/220px-Cajal_Retina.jpg" width="268" /></a><figcaption><a class="mw-redirect" href="https://en.wikipedia.org/wiki/S._Ram%C3%B3n_y_Cajal" title="S. Ramón y Cajal">S. Ramón y Cajal</a>, <i>Structure of the <a href="https://en.wikipedia.org/wiki/Mammal" title="Mammal">Mammalian</a> Retina, 1900</i></figcaption></figure>
<h4><span class="mw-headline" id="Retina">Retina</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">Retina</a></div>
<p>The retina consists of many <a href="https://en.wikipedia.org/wiki/Photoreceptor_cell" title="Photoreceptor cell">photoreceptor cells</a> which contain particular <a href="https://en.wikipedia.org/wiki/Protein" title="Protein">protein</a> <a href="https://en.wikipedia.org/wiki/Molecule" title="Molecule">molecules</a> called <a href="https://en.wikipedia.org/wiki/Opsin" title="Opsin">opsins</a>. In humans, two types of opsins are involved in conscious vision: <a href="https://en.wikipedia.org/wiki/Rod_cell" title="Rod cell">rod opsins</a> and <a href="https://en.wikipedia.org/wiki/Cone_cell" title="Cone cell">cone opsins</a>. (A third type, <a href="https://en.wikipedia.org/wiki/Melanopsin" title="Melanopsin">melanopsin</a> in some <a href="https://en.wikipedia.org/wiki/Retinal_ganglion_cell" title="Retinal ganglion cell">retinal ganglion cells</a> (RGC), part of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Body_clock" title="Body clock">body clock</a> mechanism, is probably not involved in conscious vision, as these RGC do not project to the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a> but to the <a href="https://en.wikipedia.org/wiki/Pretectal_area" title="Pretectal area">pretectal olivary nucleus</a>.) An opsin absorbs a <a href="https://en.wikipedia.org/wiki/Photon" title="Photon">photon</a> (a particle of light) and transmits a signal to the <a href="https://en.wikipedia.org/wiki/Cell_(biology)" title="Cell (biology)">cell</a> through a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Signal_transduction_pathway" title="Signal transduction pathway">signal transduction pathway</a>, resulting in hyper-polarization of the photoreceptor.
</p><p>Rods and cones differ in function. Rods are found primarily in
the periphery of the retina and are used to see at low levels of light.
Each human eye contains 120 million rods. Cones are found primarily in
the center (or <a href="https://en.wikipedia.org/wiki/Fovea_centralis" title="Fovea centralis">fovea</a>) of the retina. There are three types of cones that differ in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Wavelengths" title="Wavelengths">wavelengths</a>
of light they absorb; they are usually called short or blue, middle or
green, and long or red. Cones mediate day vision and can distinguish <a href="https://en.wikipedia.org/wiki/Color" title="Color">color</a>
and other features of the visual world at medium and high light levels.
Cones are larger and much less numerous than rods (there are 6-7
million of them in each human eye).
</p><p>In the retina, the photoreceptors <a href="https://en.wikipedia.org/wiki/Synapse" title="Synapse">synapse</a> directly onto <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bipolar_cell_of_the_retina" title="Bipolar cell of the retina">bipolar cells</a>, which in turn synapse onto <a href="https://en.wikipedia.org/wiki/Retinal_ganglion_cell" title="Retinal ganglion cell">ganglion cells</a> of the outermost layer, which then conduct <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Action_potentials" title="Action potentials">action potentials</a> to the <a href="https://en.wikipedia.org/wiki/Brain" title="Brain">brain</a>. A significant amount of <a href="https://en.wikipedia.org/wiki/Visual_processing" title="Visual processing">visual processing</a> arises from the patterns of communication between <a href="https://en.wikipedia.org/wiki/Neuron" title="Neuron">neurons</a> in the retina. About 130 million photo-receptors absorb light, yet roughly 1.2 million <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Axons" title="Axons">axons</a>
of ganglion cells transmit information from the retina to the brain.
The processing in the retina includes the formation of center-surround <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Receptive_fields" title="Receptive fields">receptive fields</a>
of bipolar and ganglion cells in the retina, as well as convergence and
divergence from photoreceptor to bipolar cell. In addition, other
neurons in the retina, particularly <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Horizontal_cell" title="Horizontal cell">horizontal</a> and <a href="https://en.wikipedia.org/wiki/Amacrine_cell" title="Amacrine cell">amacrine cells</a>,
transmit information laterally (from a neuron in one layer to an
adjacent neuron in the same layer), resulting in more complex receptive
fields that can be either indifferent to color and sensitive to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Motion_(physics)" title="Motion (physics)">motion</a> or sensitive to color and indifferent to motion.
</p>
<h5><span class="mw-headline" id="Mechanism_of_generating_visual_signals">Mechanism of generating visual signals</span></h5><p>The retina adapts to change in light through the use of the rods. In the dark, the <a href="https://en.wikipedia.org/wiki/Chromophore" title="Chromophore">chromophore</a> <a href="https://en.wikipedia.org/wiki/Retinal" title="Retinal">retinal</a> has a bent shape called cis-retinal (referring to a <i>cis</i>
conformation in one of the double bonds). When light interacts with the
retinal, it changes conformation to a straight form called
trans-retinal and breaks away from the opsin. This is called bleaching
because the purified <a href="https://en.wikipedia.org/wiki/Rhodopsin" title="Rhodopsin">rhodopsin</a> changes from violet to colorless in the light. At baseline in the dark, the rhodopsin absorbs no light and releases <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Glutamate" title="Glutamate">glutamate</a>,
which inhibits the bipolar cell. This inhibits the release of
neurotransmitters from the bipolar cells to the ganglion cell. When
there is light present, glutamate secretion ceases, thus no longer
inhibiting the bipolar cell from releasing neurotransmitters to the
ganglion cell and therefore an image can be detected.
</p><p>The final result of all this processing is five different
populations of ganglion cells that send visual (image-forming and
non-image-forming) information to the brain:
</p>
<ol><li>M cells, with large center-surround receptive fields that are sensitive to <a href="https://en.wikipedia.org/wiki/Depth_perception" title="Depth perception">depth</a>, indifferent to color, and rapidly adapt to a stimulus;</li><li>P cells, with smaller center-surround receptive fields that are sensitive to color and <a href="https://en.wikipedia.org/wiki/Shape" title="Shape">shape</a>;</li><li>K cells, with very large center-only receptive fields that are sensitive to color and indifferent to shape or depth;</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Photosensitive_ganglion_cell" title="Photosensitive ganglion cell">another population that is intrinsically photosensitive</a>; and</li><li>a final population that is used for eye movements.</li></ol>
<p>A 2006 <a href="https://en.wikipedia.org/wiki/University_of_Pennsylvania" title="University of Pennsylvania">University of Pennsylvania</a> study calculated the approximate <a href="https://en.wikipedia.org/wiki/Bandwidth_(computing)" title="Bandwidth (computing)">bandwidth</a> of human retinas to be about 8960 <a href="https://en.wikipedia.org/wiki/Kilobit" title="Kilobit">kilobits</a> per second, whereas <a href="https://en.wikipedia.org/wiki/Guinea_pig" title="Guinea pig">guinea pig</a> retinas transfer at about 875 kilobits.
</p><p>In 2007 Zaidi and co-researchers on both sides of the Atlantic
studying patients without rods and cones, discovered that the novel
photoreceptive ganglion cell in humans also has a role in conscious and
unconscious visual perception. The peak <a href="https://en.wikipedia.org/wiki/Spectral_sensitivity" title="Spectral sensitivity">spectral sensitivity</a>
was 481 nm. This shows that there are two pathways for vision in the
retina – one based on classic photoreceptors (rods and cones) and the
other, newly discovered, based on photo-receptive ganglion cells which
act as rudimentary visual brightness detectors.
</p>
<h4><span class="mw-headline" id="Photochemistry">Photochemistry</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Visual_cycle" title="Visual cycle">Visual cycle</a></div>
<p>The functioning of a <a href="https://en.wikipedia.org/wiki/Camera" title="Camera">camera</a> is often compared with the workings of the eye, mostly since both focus light from external objects in the <a href="https://en.wikipedia.org/wiki/Field_of_view" title="Field of view">field of view</a>
onto a light-sensitive medium. In the case of the camera, this medium
is film or an electronic sensor; in the case of the eye, it is an array
of visual receptors. With this simple geometrical similarity, based on
the laws of optics, the eye functions as a <a href="https://en.wikipedia.org/wiki/Transducer" title="Transducer">transducer</a>, as does a <a href="https://en.wikipedia.org/wiki/Charge-coupled_device" title="Charge-coupled device">CCD camera</a>.
</p><p>In the visual system, <b>retinal</b>, technically called <i><a href="https://en.wikipedia.org/wiki/Retinene" title="Retinene">retinene</a></i><sub>1</sub> or "retinaldehyde", is a light-sensitive molecule found in the rods and cones of the <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">retina</a>. Retinal is the fundamental structure involved in the transduction of <a href="https://en.wikipedia.org/wiki/Light" title="Light">light</a> into visual signals, i.e. nerve impulses in the ocular system of the <a href="https://en.wikipedia.org/wiki/Central_nervous_system" title="Central nervous system">central nervous system</a>. In the presence of light, the retinal molecule changes configuration and as a result, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Nerve_impulse" title="Nerve impulse">nerve impulse</a> is generated.
</p>
<h3><span class="mw-headline" id="Optic_nerve">Optic nerve</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Optic_nerve" title="Optic nerve">Optic nerve</a></div>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:1543,Vesalius%27Fabrica,VisualSystem,V1.jpg"><img class="mw-file-element" data-file-height="309" data-file-width="286" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/84/1543%2CVesalius%27Fabrica%2CVisualSystem%2CV1.jpg/220px-1543%2CVesalius%27Fabrica%2CVisualSystem%2CV1.jpg" width="370" /></a><figcaption>Information flow from the <a href="https://en.wikipedia.org/wiki/Eye" title="Eye">eyes</a> (top), crossing at the <a href="https://en.wikipedia.org/wiki/Optic_chiasm" title="Optic chiasm">optic chiasma</a>, joining left and right eye information in the <a href="https://en.wikipedia.org/wiki/Optic_tract" title="Optic tract">optic tract</a>, and layering left and right visual stimuli in the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a>. <a href="https://en.wikipedia.org/wiki/Visual_cortex#Primary_visual_cortex_(V1)" title="Visual cortex">V1</a> in red at bottom of image. (1543 image from <a href="https://en.wikipedia.org/wiki/Andreas_Vesalius" title="Andreas Vesalius">Andreas Vesalius</a>' <i>Fabrica</i>)</figcaption></figure>
<p>The information about the image via the eye is transmitted to the brain along the <a href="https://en.wikipedia.org/wiki/Optic_nerve" title="Optic nerve">optic nerve</a>.
Different populations of ganglion cells in the retina send information
to the brain through the optic nerve. About 90% of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Axons" title="Axons">axons</a> in the optic nerve go to the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a> in the <a href="https://en.wikipedia.org/wiki/Thalamus" title="Thalamus">thalamus</a>. These axons originate from the M, P, and K ganglion cells in the retina, see above. This <a href="https://en.wikipedia.org/wiki/Parallel_processing_(psychology)" title="Parallel processing (psychology)">parallel processing</a> is important for reconstructing the visual world; each type of information will go through a different route to <a href="https://en.wikipedia.org/wiki/Perception" title="Perception">perception</a>. Another population sends information to the <a href="https://en.wikipedia.org/wiki/Superior_colliculus" title="Superior colliculus">superior colliculus</a> in the <a href="https://en.wikipedia.org/wiki/Midbrain" title="Midbrain">midbrain</a>, which assists in controlling eye movements (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Saccades" title="Saccades">saccades</a>) as well as other motor responses.
</p><p>A final population of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Photosensitive_ganglion_cell" title="Photosensitive ganglion cell">photosensitive ganglion cells</a>, containing <a href="https://en.wikipedia.org/wiki/Melanopsin" title="Melanopsin">melanopsin</a> for <a href="https://en.wikipedia.org/wiki/Photosensitivity" title="Photosensitivity">photosensitivity</a>, sends information via the <a href="https://en.wikipedia.org/wiki/Retinohypothalamic_tract" title="Retinohypothalamic tract">retinohypothalamic tract</a> to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pretectum" title="Pretectum">pretectum</a> (<a href="https://en.wikipedia.org/wiki/Pupillary_reflex" title="Pupillary reflex">pupillary reflex</a>), to several structures involved in the control of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Circadian_rhythms" title="Circadian rhythms">circadian rhythms</a> and <a href="https://en.wikipedia.org/wiki/Sleep" title="Sleep">sleep</a> such as the <a href="https://en.wikipedia.org/wiki/Suprachiasmatic_nucleus" title="Suprachiasmatic nucleus">suprachiasmatic nucleus</a> (the biological clock), and to the <a href="https://en.wikipedia.org/wiki/Ventrolateral_preoptic_nucleus" title="Ventrolateral preoptic nucleus">ventrolateral preoptic nucleus</a> (a region involved in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sleep_regulation" title="Sleep regulation">sleep regulation</a>).<sup class="reference" id="cite_ref-32"><a href="https://en.wikipedia.org/wiki/Visual_system#cite_note-32">[32]</a></sup>
A recently discovered role for photoreceptive ganglion cells is that
they mediate conscious and unconscious vision – acting as rudimentary
visual brightness detectors as shown in rodless coneless eyes.
</p>
<h3><span class="mw-headline" id="Optic_chiasm">Optic chiasm</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Optic_chiasm" title="Optic chiasm">Optic chiasm</a></div>
<p>The optic nerves from both eyes meet and cross at the optic chiasm, at the base of the <a href="https://en.wikipedia.org/wiki/Hypothalamus" title="Hypothalamus">hypothalamus</a> of the brain. At this point, the information coming from both eyes is combined and then splits according to the <a href="https://en.wikipedia.org/wiki/Visual_field" title="Visual field">visual field</a>. The corresponding halves of the field of view (right and left) are sent to the left and right <a href="https://en.wikipedia.org/wiki/Cerebral_hemisphere" title="Cerebral hemisphere">halves of the brain</a>, respectively, to be processed. That is, the right side of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Primary_visual_cortex" title="Primary visual cortex">primary visual cortex</a> deals with the left half of the <i>field of view</i> from both eyes, and similarly for the left brain. A small region in the center of the field of view is processed redundantly by both halves of the brain.
</p>
<h3><span class="mw-headline" id="Optic_tract">Optic tract</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Optic_tract" title="Optic tract">Optic tract</a></div>
<p>Information from the right <i>visual field</i> (now on the left side of the brain) travels in the left optic tract. Information from the left <i>visual field</i> travels in the right optic tract. Each optic tract terminates in the <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a> (LGN) in the thalamus.
</p>
<figure class="mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lateral_geniculate_nucleus.png"><img class="mw-file-element" data-file-height="259" data-file-width="300" height="346" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Lateral_geniculate_nucleus.png/200px-Lateral_geniculate_nucleus.png" width="400" /></a><figcaption>Six layers in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lgn" title="Lgn">LGN</a></figcaption></figure>
<h3><span class="mw-headline" id="Lateral_geniculate_nucleus">Lateral geniculate nucleus</span></h3><dl><dd><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">Lateral geniculate nucleus</a></div></dd></dl>
<p>The <b>lateral geniculate nucleus</b> (LGN) is a sensory relay nucleus in the thalamus of the brain. The LGN consists of six layers in <a href="https://en.wikipedia.org/wiki/Human" title="Human">humans</a> and other <a href="https://en.wikipedia.org/wiki/Primate" title="Primate">primates</a> starting from <a href="https://en.wikipedia.org/wiki/Catarrhini" title="Catarrhini">catarrhines</a>, including <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cercopithecidae" title="Cercopithecidae">cercopithecidae</a> and <a href="https://en.wikipedia.org/wiki/Ape" title="Ape">apes</a>.
Layers 1, 4, and 6 correspond to information from the contralateral
(crossed) fibers of the nasal retina (temporal visual field); layers 2,
3, and 5 correspond to <a href="https://en.wikipedia.org/wiki/Information" title="Information">information</a>
from the ipsilateral (uncrossed) fibers of the temporal retina (nasal
visual field). Layer one contains M cells, which correspond to the M (<a href="https://en.wikipedia.org/wiki/Magnocellular_cell" title="Magnocellular cell">magnocellular</a>)
cells of the optic nerve of the opposite eye and are concerned with
depth or motion. Layers four and six of the LGN also connect to the
opposite eye, but to the P cells (color and edges) of the optic nerve.
By contrast, layers two, three and five of the LGN connect to the M
cells and P (<a href="https://en.wikipedia.org/wiki/Parvocellular_cell" title="Parvocellular cell">parvocellular</a>)
cells of the optic nerve for the same side of the brain as its
respective LGN. Spread out, the six layers of the LGN are the area of a <a href="https://en.wikipedia.org/wiki/Credit_card" title="Credit card">credit card</a> and about three times its thickness. The LGN is rolled up into two <a href="https://en.wikipedia.org/wiki/Ellipsoid" title="Ellipsoid">ellipsoids</a>
about the size and shape of two small birds' eggs. In between the six
layers are smaller cells that receive information from the K cells
(color) in the retina. The neurons of the LGN then relay the visual
image to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Primary_visual_cortex" title="Primary visual cortex">primary visual cortex</a> (V1) which is located at the back of the brain (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Posterior_(anatomy)" title="Posterior (anatomy)">posterior end</a>) in the <a href="https://en.wikipedia.org/wiki/Occipital_lobe" title="Occipital lobe">occipital lobe</a> in and close to the <a href="https://en.wikipedia.org/wiki/Calcarine_sulcus" title="Calcarine sulcus">calcarine sulcus</a>. The LGN is not just a simple relay station, but it is also a center for processing; it receives reciprocal input from the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cortical_layer" title="Cortical layer">cortical</a> and subcortical layers and <a href="https://en.wikipedia.org/wiki/Reciprocal_innervation" title="Reciprocal innervation">reciprocal innervation</a> from the visual cortex.
</p>
<figure class="mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lisa_analysis.png"><img class="mw-file-element" data-file-height="556" data-file-width="404" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Lisa_analysis.png/200px-Lisa_analysis.png" width="291" /></a><figcaption>Scheme of the <a href="https://en.wikipedia.org/wiki/Optic_tract" title="Optic tract">optic tract</a> with image being decomposed on the way, up to simple cortical cells (simplified)</figcaption></figure>
<h3><span class="mw-headline" id="Optic_radiation">Optic radiation</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Optic_radiation" title="Optic radiation">Optic radiation</a></div>
<p>The <b>optic radiations</b>, one on each side of the brain, carry information from the thalamic <a href="https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus" title="Lateral geniculate nucleus">lateral geniculate nucleus</a> to layer 4 of the <a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">visual cortex</a>.
The P layer neurons of the LGN relay to V1 layer 4C β. The M layer
neurons relay to V1 layer 4C α. The K layer neurons in the LGN relay to
large neurons called blobs in layers 2 and 3 of V1.
</p><p>There is a direct correspondence from an angular position in the <a href="https://en.wikipedia.org/wiki/Visual_field" title="Visual field">visual field</a>
of the eye, all the way through the optic tract to a nerve position in
V1 (up to V4, i.e. the primary visual areas. After that, the visual
pathway is roughly separated into a <a href="https://en.wikipedia.org/wiki/Two-streams_hypothesis" title="Two-streams hypothesis">ventral and dorsal pathway</a>).
</p>
<h3><span class="mw-headline" id="Visual_cortex">Visual cortex</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">Visual cortex</a></div>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Brodmann_areas_17_18_19.png"><img class="mw-file-element" data-file-height="192" data-file-width="256" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Brodmann_areas_17_18_19.png/200px-Brodmann_areas_17_18_19.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">Visual cortex</a>: <br />V1; V2; V3; V4; V5 (also called MT)</figcaption></figure>
<p>The visual cortex is the largest system in the human brain and is
responsible for processing the visual image. It lies at the rear of the
brain (highlighted in the image), above the <a href="https://en.wikipedia.org/wiki/Cerebellum" title="Cerebellum">cerebellum</a>. The region that receives information directly from the LGN is called the <a href="https://en.wikipedia.org/wiki/Visual_cortex#Primary_visual_cortex_(V1)" title="Visual cortex">primary visual cortex</a>,
(also called V1 and striate cortex). It creates a bottom-up saliency
map of the visual field to guide attention or eye gaze to salient visual
locations, hence selection of visual input information by attention starts at V1
along the visual pathway. Visual information then flows through a
cortical hierarchy. These areas include V2, V3, V4 and area V5/MT (the
exact connectivity depends on the species of the animal). These
secondary visual areas (collectively termed the extrastriate visual
cortex) process a wide variety of visual primitives. Neurons in V1 and
V2 respond selectively to bars of specific orientations, or combinations
of bars. These are believed to support edge and corner detection.
Similarly, basic information about color and motion is processed here.
</p><p>Heider, et al. (2002) have found that neurons involving V1, V2, and V3 can detect stereoscopic <a href="https://en.wikipedia.org/wiki/Illusory_contours" title="Illusory contours">illusory contours</a>; they found that stereoscopic stimuli subtending up to 8° can activate these neurons.
</p>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:RestingStateModels.jpg"><img class="mw-file-element" data-file-height="847" data-file-width="796" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/RestingStateModels.jpg/220px-RestingStateModels.jpg" width="376" /></a><figcaption>Visual cortex is active even during <a href="https://en.wikipedia.org/wiki/Resting_state_fMRI" title="Resting state fMRI">resting state fMRI</a>.</figcaption></figure>
<h3><span class="mw-headline" id="Visual_association_cortex">Visual association cortex</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Two-streams_hypothesis" title="Two-streams hypothesis">Two-streams hypothesis</a></div>
<p>As visual information passes forward through the visual hierarchy,
the complexity of the neural representations increases. Whereas a V1
neuron may respond selectively to a line segment of a particular
orientation in a particular <a href="https://en.wikipedia.org/wiki/Retinotopy" title="Retinotopy">retinotopic</a>
location, neurons in the lateral occipital complex respond selectively
to complete object (e.g., a figure drawing), and neurons in visual
association cortex may respond selectively to human faces, or to a
particular object.
</p><p>Along with this increasing complexity of neural representation
may come a level of specialization of processing into two distinct
pathways: the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dorsal_stream" title="Dorsal stream">dorsal stream</a> and the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ventral_stream" title="Ventral stream">ventral stream</a> (the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Two_Streams_hypothesis" title="Two Streams hypothesis">Two Streams hypothesis</a>,
first proposed by Ungerleider and Mishkin in 1982). The dorsal stream,
commonly referred to as the "where" stream, is involved in spatial
attention (covert and overt), and communicates with regions that control
eye movements and hand movements. More recently, this area has been
called the "how" stream to emphasize its role in guiding behaviors to
spatial locations. The ventral stream, commonly referred to as the
"what" stream, is involved in the recognition, identification and
categorization of visual stimuli.
</p>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Gray726_intraparietal_sulcus.svg"><img class="mw-file-element" data-file-height="573" data-file-width="992" height="231" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Gray726_intraparietal_sulcus.svg/220px-Gray726_intraparietal_sulcus.svg.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Intraparietal_sulcus" title="Intraparietal sulcus">Intraparietal sulcus</a> (red)</figcaption></figure>
<p>However, there is still much debate about the degree of
specialization within these two pathways, since they are in fact heavily
interconnected.
</p><p><a href="https://en.wikipedia.org/wiki/Horace_Barlow" title="Horace Barlow">Horace Barlow</a> proposed the <i><a href="https://en.wikipedia.org/wiki/Efficient_coding_hypothesis" title="Efficient coding hypothesis">efficient coding hypothesis</a></i> in 1961 as a theoretical model of <a href="https://en.wikipedia.org/wiki/Sensory_neuroscience" title="Sensory neuroscience">sensory coding</a> in the <a href="https://en.wikipedia.org/wiki/Brain" title="Brain">brain</a>. Limitations in the applicability of this theory in the <a class="external text" href="http://www.scholarpedia.org/article/Area_V1" rel="nofollow">primary visual cortex (V1)</a> motivated the <a href="https://en.wikipedia.org/wiki/V1_Saliency_Hypothesis" title="V1 Saliency Hypothesis">V1 Saliency Hypothesis</a> that V1 creates a bottom-up saliency map to guide attention exogenously. With attentional selection as a center stage, vision is seen as composed of encoding, selection, and decoding stages.
</p><p>The <a href="https://en.wikipedia.org/wiki/Default_mode_network" title="Default mode network">default mode network</a>
is a network of brain regions that are active when an individual is
awake and at rest. The visual system's default mode can be monitored
during <a href="https://en.wikipedia.org/wiki/Resting_state_fMRI" title="Resting state fMRI">resting state fMRI</a>:
Fox, et al. (2005) have found that "<a class="external text" href="http://www.pnas.org/content/102/27/9673.full" rel="nofollow">The human brain is intrinsically organized into dynamic, anticorrelated functional networks'"</a>, in which the visual system switches from resting state to attention.
</p><p>In the <a href="https://en.wikipedia.org/wiki/Parietal_lobe" title="Parietal lobe">parietal lobe</a>, the <a href="https://en.wikipedia.org/wiki/Lateral_intraparietal_cortex" title="Lateral intraparietal cortex">lateral</a> and ventral intraparietal cortex are involved in visual attention and saccadic eye movements. These regions are in the <a href="https://en.wikipedia.org/wiki/Intraparietal_sulcus" title="Intraparietal sulcus">Intraparietal sulcus</a> (marked in red in the adjacent image).
</p>
<h2><span class="mw-headline" id="Development">Development</span></h2><h3><span class="mw-headline" id="Infancy">Infancy</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Infant_vision" title="Infant vision">Infant vision</a></div>
<p>Newborn infants have limited <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Color_perception" title="Color perception">color perception</a>.
One study found that 74% of newborns can distinguish red, 36% green,
25% yellow, and 14% blue. After one month, performance "improved
somewhat." Infant's eyes do not have the ability to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Accommodation_(eye)" title="Accommodation (eye)">accommodate</a>. The pediatricians are able to perform non-verbal testing to assess <a href="https://en.wikipedia.org/wiki/Visual_acuity" title="Visual acuity">visual acuity</a> of a newborn, detect <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Nearsightedness" title="Nearsightedness">nearsightedness</a> and <a href="https://en.wikipedia.org/wiki/Astigmatism" title="Astigmatism">astigmatism</a>,
and evaluate the eye teaming and alignment. Visual acuity improves from
about 20/400 at birth to approximately 20/25 at 6 months of age. All
this is happening because the nerve cells in their <a href="https://en.wikipedia.org/wiki/Retina" title="Retina">retina</a> and brain that control vision are not fully developed.
</p>
<h3><span class="mw-headline" id="Childhood_and_adolescence">Childhood and adolescence</span></h3><p><a href="https://en.wikipedia.org/wiki/Depth_perception" title="Depth perception">Depth perception</a>,
focus, tracking and other aspects of vision continue to develop
throughout early and middle childhood. From recent studies in the <a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a> and <a href="https://en.wikipedia.org/wiki/Australia" title="Australia">Australia</a>
there is some evidence that the amount of time school aged children
spend outdoors, in natural light, may have some impact on whether they
develop <a href="https://en.wikipedia.org/wiki/Myopia" title="Myopia">myopia</a>.
The condition tends to get somewhat worse through childhood and
adolescence, but stabilizes in adulthood. More prominent myopia
(nearsightedness) and astigmatism are thought to be inherited. Children
with this condition may need to wear glasses.
</p>
<h3><span class="mw-headline" id="Adulthood">Adulthood</span></h3><p>Vision is often one of the first senses affected by aging. A number of changes occur with aging:
</p>
<ul><li>Over time, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lens_(anatomy)" title="Lens (anatomy)">lens</a> become yellowed and may eventually become brown, a condition known as brunescence or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Brunescent_cataract" title="Brunescent cataract">brunescent</a> <a href="https://en.wikipedia.org/wiki/Cataract" title="Cataract">cataract</a>. Although many factors contribute to yellowing, lifetime exposure to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ultraviolet_light" title="Ultraviolet light">ultraviolet light</a> and <a href="https://en.wikipedia.org/wiki/Ageing" title="Ageing">aging</a> are two main causes.</li><li>The lens becomes less flexible, diminishing the ability to accommodate (<a href="https://en.wikipedia.org/wiki/Presbyopia" title="Presbyopia">presbyopia</a>).</li><li>While a healthy adult pupil typically has a size range of 2–8 mm,
with age the range gets smaller, trending towards a moderately small
diameter.</li><li>On average <a href="https://en.wikipedia.org/wiki/Tears" title="Tears">tear production</a> declines with age. However, there are a number of age-related conditions that can cause excessive tearing.</li></ul>
<h2><span class="mw-headline" id="Other_functions">Other functions</span></h2><h3><span class="mw-headline" id="Balance">Balance</span></h3><p>Along with <a href="https://en.wikipedia.org/wiki/Proprioception" title="Proprioception">proprioception</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Vestibular_function" title="Vestibular function">vestibular function</a>,
the visual system plays an important role in the ability of an
individual to control balance and maintain an upright posture. When
these three conditions are isolated and balance is tested, it has been
found that vision is the most significant contributor to balance,
playing a bigger role than either of the two other intrinsic mechanisms.
The clarity with which an individual can see his environment, as well
as the size of the visual field, the susceptibility of the individual to
light and glare, and poor depth perception play important roles in
providing a feedback loop to the brain on the body's movement through
the environment. Anything that affects any of these variables can have a
negative effect on balance and maintaining posture. This effect has been seen in research involving elderly subjects when compared to young controls, in <a href="https://en.wikipedia.org/wiki/Glaucoma" title="Glaucoma">glaucoma</a> patients compared to age matched controls, <a href="https://en.wikipedia.org/wiki/Cataract" title="Cataract">cataract</a> patients pre and post surgery, and even something as simple as wearing safety goggles. <a href="https://en.wikipedia.org/wiki/Monocular_vision" title="Monocular vision">Monocular vision</a>
(one eyed vision) has also been shown to negatively impact balance,
which was seen in the previously referenced cataract and glaucoma
studies, as well as in healthy children and adults.
</p><p>According to Pollock et al. (2010) <a href="https://en.wikipedia.org/wiki/Stroke" title="Stroke">stroke</a> is the main cause of specific visual impairment, most frequently visual field loss (<a href="https://en.wikipedia.org/wiki/Homonymous_hemianopsia" title="Homonymous hemianopsia">homonymous hemianopia</a>,
a visual field defect). Nevertheless, evidence for the efficacy of
cost-effective interventions aimed at these visual field defects is
still inconsistent.
</p>
<h2><span class="mw-headline" id="Clinical_significance">Clinical significance</span></h2><figure class="mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Hemianopsia_en.jpg"><img class="mw-file-element" data-file-height="600" data-file-width="604" height="398" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Hemianopsia_en.jpg/350px-Hemianopsia_en.jpg" width="400" /></a><figcaption><b><a href="https://en.wikipedia.org/wiki/Visual_pathway_lesions" title="Visual pathway lesions">Visual pathway lesions</a></b> <br /> From top to bottom: <br /> 1. Complete loss of vision, right eye <br /> 2. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bitemporal_hemianopia" title="Bitemporal hemianopia">Bitemporal hemianopia</a> <br /> 3. <a href="https://en.wikipedia.org/wiki/Homonymous_hemianopsia" title="Homonymous hemianopsia">Homonymous hemianopsia</a> <br /> 4. <a href="https://en.wikipedia.org/wiki/Quadrantanopia" title="Quadrantanopia">Quadrantanopia</a> <br /> 5&6. Quadrantanopia with <a href="https://en.wikipedia.org/wiki/Macular_sparing" title="Macular sparing">macular sparing</a></figcaption></figure>
<p>Proper function of the visual system is required for sensing,
processing, and understanding the surrounding environment. Difficulty in
sensing, processing and understanding light input has the potential to
adversely impact an individual's ability to communicate, learn and
effectively complete routine tasks on a daily basis.
</p><p>In children, early diagnosis and treatment of impaired visual
system function is an important factor in ensuring that key social,
academic and speech/language developmental milestones are met.
</p><p><a href="https://en.wikipedia.org/wiki/Cataract" title="Cataract">Cataract</a>
is clouding of the lens, which in turn affects vision. Although it may
be accompanied by yellowing, clouding and yellowing can occur
separately. This is typically a result of ageing, disease, or drug use.
</p><p><a href="https://en.wikipedia.org/wiki/Presbyopia" title="Presbyopia">Presbyopia</a> is a visual condition that causes <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Far-sightedness" title="Far-sightedness">farsightedness</a>. The eye's lens becomes too inflexible to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Accommodation_(eye)" title="Accommodation (eye)">accommodate</a> to normal reading distance, focus tending to remain fixed at long distance.
</p><p><a href="https://en.wikipedia.org/wiki/Glaucoma" title="Glaucoma">Glaucoma</a> is a type of blindness that begins at the edge of the visual field and progresses inward. It may result in <a href="https://en.wikipedia.org/wiki/Tunnel_vision" title="Tunnel vision">tunnel vision</a>.
This typically involves the outer layers of the optic nerve, sometimes
as a result of buildup of fluid and excessive pressure in the eye.
</p><p><a href="https://en.wikipedia.org/wiki/Scotoma" title="Scotoma">Scotoma</a> is a type of blindness that produces a small <a href="https://en.wikipedia.org/wiki/Blind_spot_(vision)" title="Blind spot (vision)">blind spot</a> in the visual field typically caused by injury in the primary visual cortex.
</p><p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Homonymous_hemianopia" title="Homonymous hemianopia">Homonymous hemianopia</a>
is a type of blindness that destroys one entire side of the visual
field typically caused by injury in the primary visual cortex.
</p><p><a href="https://en.wikipedia.org/wiki/Quadrantanopia" title="Quadrantanopia">Quadrantanopia</a>
is a type of blindness that destroys only a part of the visual field
typically caused by partial injury in the primary visual cortex. This is
very similar to homonymous hemianopia, but to a lesser degree.
</p><p><a href="https://en.wikipedia.org/wiki/Prosopagnosia" title="Prosopagnosia">Prosopagnosia</a>,
or face blindness, is a brain disorder that produces an inability to
recognize faces. This disorder often arises after damage to the <a href="https://en.wikipedia.org/wiki/Fusiform_face_area" title="Fusiform face area">fusiform face area</a>.
</p><p><a href="https://en.wikipedia.org/wiki/Visual_agnosia" title="Visual agnosia">Visual agnosia</a>,
or visual-form agnosia, is a brain disorder that produces an inability
to recognize objects. This disorder often arises after damage to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ventral_stream" title="Ventral stream">ventral stream</a>.
</p>
<h2><span class="mw-headline" id="Other_animals">Other animals</span></h2><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Eye" title="Eye">Eye</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Vision_in_birds" title="Vision in birds">Vision in birds</a>, <a href="https://en.wikipedia.org/wiki/Parietal_eye" title="Parietal eye">Parietal eye</a>, <a href="https://en.wikipedia.org/wiki/Vision_in_fish" title="Vision in fish">Vision in fish</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arthropod_visual_system" title="Arthropod visual system">Arthropod visual system</a>, and <a href="https://en.wikipedia.org/wiki/Cephalopod_eye" title="Cephalopod eye">Cephalopod eye</a></div>
<p>Different <a href="https://en.wikipedia.org/wiki/Species" title="Species">species</a> are able to see different parts of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Light_spectrum" title="Light spectrum">light spectrum</a>; for example, <a href="https://en.wikipedia.org/wiki/Bee" title="Bee">bees</a> can see into the <a href="https://en.wikipedia.org/wiki/Ultraviolet" title="Ultraviolet">ultraviolet</a>, while <a href="https://en.wikipedia.org/wiki/Pit_viper" title="Pit viper">pit vipers</a> can accurately target prey with their <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pit_organ" title="Pit organ">pit organs</a>, which are sensitive to infrared radiation. The <a href="https://en.wikipedia.org/wiki/Mantis_shrimp" title="Mantis shrimp">mantis shrimp</a>
possesses arguably the most complex visual system of any species. The
eye of the mantis shrimp holds 16 color receptive cones, whereas humans
only have three. The variety of cones enables them to perceive an
enhanced array of colors as a mechanism for mate selection, avoidance of
predators, and detection of prey. Swordfish also possess an impressive visual system. The eye of a <a href="https://en.wikipedia.org/wiki/Swordfish" title="Swordfish">swordfish</a> can generate <a href="https://en.wikipedia.org/wiki/Heat" title="Heat">heat</a> to better cope with detecting their <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Prey" title="Prey">prey</a> at depths of 2000 feet. Certain <a class="mw-redirect" href="https://en.wikipedia.org/wiki/One-celled" title="One-celled">one-celled</a> <a href="https://en.wikipedia.org/wiki/Microorganism" title="Microorganism">microorganisms</a>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Warnowiid" title="Warnowiid">warnowiid</a> <a href="https://en.wikipedia.org/wiki/Dinoflagellate" title="Dinoflagellate">dinoflagellates</a> have eye-like <a href="https://en.wikipedia.org/wiki/Ocelloid" title="Ocelloid">ocelloids</a>, with analogous structures for the lens and retina of the multi-cellular eye. The armored shell of the <a href="https://en.wikipedia.org/wiki/Chiton" title="Chiton">chiton</a> <i><a href="https://en.wikipedia.org/wiki/Acanthopleura_granulata" title="Acanthopleura granulata">Acanthopleura granulata</a></i> is also covered with hundreds of <a href="https://en.wikipedia.org/wiki/Aragonite" title="Aragonite">aragonite</a> crystalline eyes, named <a href="https://en.wikipedia.org/wiki/Simple_eye_in_invertebrates" title="Simple eye in invertebrates">ocelli</a>, which can form <a href="https://en.wikipedia.org/wiki/Image" title="Image">images</a>.
</p><p>Many <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fan_worm" title="Fan worm">fan worms</a>, such as <i><a href="https://en.wikipedia.org/wiki/Acromegalomma_interruptum" title="Acromegalomma interruptum">Acromegalomma interruptum</a></i> which live in tubes on the sea floor of the <a href="https://en.wikipedia.org/wiki/Great_Barrier_Reef" title="Great Barrier Reef">Great Barrier Reef</a>,
have evolved compound eyes on their tentacles, which they use to detect
encroaching movement. If movement is detected, the fan worms will
rapidly withdraw their tentacles. Bok, et al., have discovered opsins
and <a href="https://en.wikipedia.org/wiki/G_protein" title="G protein">G proteins</a> in the fan worm's eyes, which were previously only seen in simple <a href="https://en.wikipedia.org/wiki/Cilium" title="Cilium">ciliary</a> photoreceptors in the brains of some <a href="https://en.wikipedia.org/wiki/Invertebrate" title="Invertebrate">invertebrates</a>, as opposed to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rhabdomeric" title="Rhabdomeric">rhabdomeric</a> receptors in the eyes of most invertebrates.
</p><p>Only <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Higher_primate" title="Higher primate">higher primate</a> <a href="https://en.wikipedia.org/wiki/Old_World" title="Old World">Old World</a> (African) <a href="https://en.wikipedia.org/wiki/Monkey" title="Monkey">monkeys</a> and apes (<a href="https://en.wikipedia.org/wiki/Macaque" title="Macaque">macaques</a>, <a href="https://en.wikipedia.org/wiki/Ape" title="Ape">apes</a>, <a href="https://en.wikipedia.org/wiki/Orangutan" title="Orangutan">orangutans</a>) have the same kind of three-cone <a href="https://en.wikipedia.org/wiki/Photoreceptor_cell" title="Photoreceptor cell">photoreceptor</a> color vision humans have, while lower primate <a href="https://en.wikipedia.org/wiki/New_World" title="New World">New World</a> (South American) monkeys (<a href="https://en.wikipedia.org/wiki/Spider_monkey" title="Spider monkey">spider monkeys</a>, <a href="https://en.wikipedia.org/wiki/Squirrel_monkey" title="Squirrel monkey">squirrel monkeys</a>, <a href="https://en.wikipedia.org/wiki/Capuchin_monkey" title="Capuchin monkey">cebus monkeys</a>) have a two-cone photoreceptor kind of color vision.
</p><p>Biologists have determined that humans have extremely good vision
compared to the overwhelming majority of animals, particularly in
daylight, though a few species have better. Other animals such as <a href="https://en.wikipedia.org/wiki/Dog" title="Dog">dogs</a> are thought to rely more on senses other than vision, which in turn may be better developed than in humans.
</p>
<h2><span class="mw-headline" id="History">History</span></h2><p>In the
second half of the 19th century, many motifs of the nervous system were
identified such as the neuron doctrine and brain localization, which
related to the <a href="https://en.wikipedia.org/wiki/Neuron" title="Neuron">neuron</a>
being the basic unit of the nervous system and functional localisation
in the brain, respectively. These would become tenets of the fledgling <a href="https://en.wikipedia.org/wiki/Neuroscience" title="Neuroscience">neuroscience</a> and would support further understanding of the visual system.
</p><p>The notion that the <a href="https://en.wikipedia.org/wiki/Cerebral_cortex" title="Cerebral cortex">cerebral cortex</a> is divided into functionally distinct cortices now known to be responsible for capacities such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Touch" title="Touch">touch</a> (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Somatosensory_cortex" title="Somatosensory cortex">somatosensory cortex</a>), <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Motion_(physics)" title="Motion (physics)">movement</a> (<a href="https://en.wikipedia.org/wiki/Motor_cortex" title="Motor cortex">motor cortex</a>), and vision (<a href="https://en.wikipedia.org/wiki/Visual_cortex" title="Visual cortex">visual cortex</a>), was first proposed by <a href="https://en.wikipedia.org/wiki/Franz_Joseph_Gall" title="Franz Joseph Gall">Franz Joseph Gall</a> in 1810.
Evidence for functionally distinct areas of the brain (and,
specifically, of the cerebral cortex) mounted throughout the 19th
century with discoveries by <a href="https://en.wikipedia.org/wiki/Paul_Broca" title="Paul Broca">Paul Broca</a> of the <a href="https://en.wikipedia.org/wiki/Language_center" title="Language center">language center</a> (1861), and <a href="https://en.wikipedia.org/wiki/Gustav_Fritsch" title="Gustav Fritsch">Gustav Fritsch</a> and <a href="https://en.wikipedia.org/wiki/Eduard_Hitzig" title="Eduard Hitzig">Eduard Hitzig</a> of the motor cortex (1871). Based on selective damage to parts of the brain and the functional effects of the resulting <a href="https://en.wikipedia.org/wiki/Lesion" title="Lesion">lesions</a>, <a href="https://en.wikipedia.org/wiki/David_Ferrier" title="David Ferrier">David Ferrier</a> proposed that visual function was localized to the <a href="https://en.wikipedia.org/wiki/Parietal_lobe" title="Parietal lobe">parietal lobe</a> of the brain in 1876. In 1881, <a href="https://en.wikipedia.org/wiki/Hermann_Munk" title="Hermann Munk">Hermann Munk</a> more accurately located vision in the <a href="https://en.wikipedia.org/wiki/Occipital_lobe" title="Occipital lobe">occipital lobe</a>, where the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Primary_visual_cortex" title="Primary visual cortex">primary visual cortex</a> is now known to be.
</p><p>In 2014, a textbook "Understanding vision: theory, models, and data" illustrates how to link neurobiological data and visual
behavior/psychological data through theoretical principles and
computational models.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-69743008140974566582024-03-18T05:41:00.007-04:002024-03-18T05:41:36.348-04:00Psychosis<div class="vector-column-end">
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<div class="hatnote navigation-not-searchable" role="note"><a href="https://en.wikipedia.org/wiki/Psychosis">https://en.wikipedia.org/wiki/Psychosis</a><br /></div><br />
<table class="infobox"><tbody><tr><th class="infobox-above" colspan="2" style="background: #ccc;">Psychosis</th></tr><tr><th class="infobox-label" scope="row">Other names</th><td class="infobox-data">Psychotic break (<i>colloquial</i>)</td></tr><tr><th class="infobox-label" scope="row"><a href="https://en.wikipedia.org/wiki/Medical_specialty" title="Medical specialty">Specialty</a></th><td class="infobox-data"><a href="https://en.wikipedia.org/wiki/Psychiatry" title="Psychiatry">Psychiatry</a>, <a href="https://en.wikipedia.org/wiki/Clinical_psychology" title="Clinical psychology">clinical psychology</a></td></tr><tr><th class="infobox-label" scope="row"><a href="https://en.wikipedia.org/wiki/Signs_and_symptoms" title="Signs and symptoms">Symptoms</a></th><td class="infobox-data"><a href="https://en.wikipedia.org/wiki/Delusion" title="Delusion">False beliefs</a>, <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">seeing or hearing things that others do not see or hear</a>, incoherent speech and behavior</td></tr><tr><th class="infobox-label" scope="row"><a href="https://en.wikipedia.org/wiki/Complication_(medicine)" title="Complication (medicine)">Complications</a></th><td class="infobox-data"><a href="https://en.wikipedia.org/wiki/Self-harm" title="Self-harm">Self-harm</a>, <a href="https://en.wikipedia.org/wiki/Suicide" title="Suicide">suicide</a></td></tr><tr><th class="infobox-label" scope="row">Causes</th><td class="infobox-data"><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mental_illness" title="Mental illness">Mental illness</a> (<a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a>, <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a>), <a href="https://en.wikipedia.org/wiki/Psychological_trauma" title="Psychological trauma">trauma</a>, <a href="https://en.wikipedia.org/wiki/Sleep_deprivation" title="Sleep deprivation">sleep deprivation</a>, some medical conditions, certain <a href="https://en.wikipedia.org/wiki/Medication" title="Medication">medications</a>, drugs (including <a href="https://en.wikipedia.org/wiki/Alcohol_(drug)" title="Alcohol (drug)">alcohol</a>, <a href="https://en.wikipedia.org/wiki/Caffeine" title="Caffeine">caffeine</a> and <a href="https://en.wikipedia.org/wiki/Cannabis_(drug)" title="Cannabis (drug)">cannabis</a>)</td></tr><tr><th class="infobox-label" scope="row">Treatment</th><td class="infobox-data"><a href="https://en.wikipedia.org/wiki/Antipsychotic" title="Antipsychotic">Antipsychotics</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Counselling" title="Counselling">counselling</a>, <a href="https://en.wikipedia.org/wiki/Social_support" title="Social support">social support</a></td></tr><tr><th class="infobox-label" scope="row"><a href="https://en.wikipedia.org/wiki/Prognosis" title="Prognosis">Prognosis</a></th><td class="infobox-data">Depends on cause</td></tr><tr><th class="infobox-label" scope="row">Frequency</th><td class="infobox-data">3% of people at some point in their life (US)</td></tr></tbody></table>
<p><b>Psychosis</b> is a condition of the <a href="https://en.wikipedia.org/wiki/Mind" title="Mind">mind</a> that results in difficulties determining what is <a href="https://en.wikipedia.org/wiki/Reality" title="Reality">real</a> and what is not real. Symptoms may include <a href="https://en.wikipedia.org/wiki/Delusion" title="Delusion">delusions</a> and <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">hallucinations</a>, among other features. Additional symptoms are <a href="https://en.wikipedia.org/wiki/Thought_disorder" title="Thought disorder">incoherent speech</a> and behavior that is inappropriate for a given situation. There may also be <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sleep_problem" title="Sleep problem">sleep problems</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Social_withdrawal" title="Social withdrawal">social withdrawal</a>, lack of motivation, and difficulties carrying out <a href="https://en.wikipedia.org/wiki/Activities_of_daily_living" title="Activities of daily living">daily activities</a>. Psychosis can have serious adverse outcomes.
</p><p>As with many psychiatric phenomena, psychosis has several different causes. These include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mental_illness" title="Mental illness">mental illness</a>, such as <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a> or <a href="https://en.wikipedia.org/wiki/Schizoaffective_disorder" title="Schizoaffective disorder">schizoaffective disorder</a>, <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a>, <a href="https://en.wikipedia.org/wiki/Sensory_deprivation" title="Sensory deprivation">sensory deprivation</a>, and in rare cases <a href="https://en.wikipedia.org/wiki/Major_depressive_disorder" title="Major depressive disorder">major depression</a> (<a href="https://en.wikipedia.org/wiki/Psychotic_depression" title="Psychotic depression">psychotic depression</a>). Other causes include: <a href="https://en.wikipedia.org/wiki/Psychological_trauma" title="Psychological trauma">trauma</a>, <a href="https://en.wikipedia.org/wiki/Sleep_deprivation" title="Sleep deprivation">sleep deprivation</a>, some medical conditions, certain <a href="https://en.wikipedia.org/wiki/Medication" title="Medication">medications</a>, and drugs such as <a href="https://en.wikipedia.org/wiki/Alcohol_(drug)" title="Alcohol (drug)">alcohol</a>, <a href="https://en.wikipedia.org/wiki/Cannabis_(drug)" title="Cannabis (drug)">cannabis</a>, <a href="https://en.wikipedia.org/wiki/Hallucinogen" title="Hallucinogen">hallucinogens</a>, and <a href="https://en.wikipedia.org/wiki/Stimulant" title="Stimulant">stimulants</a>. One type, known as <a href="https://en.wikipedia.org/wiki/Postpartum_psychosis" title="Postpartum psychosis">postpartum psychosis</a>, can occur after giving birth. The <a href="https://en.wikipedia.org/wiki/Neurotransmitter" title="Neurotransmitter">neurotransmitter</a> <a href="https://en.wikipedia.org/wiki/Dopamine" title="Dopamine">dopamine</a> is believed to play an important role.
Acute psychosis is termed primary if it results from a psychiatric
condition and secondary if it is caused by another medical condition or
drugs. The diagnosis of a mental-health condition requires excluding other potential causes. Testing may be done to check for <a href="https://en.wikipedia.org/wiki/Central_nervous_system" title="Central nervous system">central nervous system</a> diseases, toxins, or other health problems as a cause.
</p><p>Treatment may include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Antipsychotic_medication" title="Antipsychotic medication">antipsychotic medication</a>, <a href="https://en.wikipedia.org/wiki/Psychotherapy" title="Psychotherapy">psychotherapy</a>, and <a href="https://en.wikipedia.org/wiki/Social_support" title="Social support">social support</a>. Early treatment appears to improve outcomes. Medications appear to have a moderate effect. Outcomes depend on the underlying cause. In the United States about 3% of people develop psychosis at some point in their lives. The condition has been described since at least the 4th century BC by <a href="https://en.wikipedia.org/wiki/Hippocrates" title="Hippocrates">Hippocrates</a> and possibly as early as 1500 BC in the Egyptian <a href="https://en.wikipedia.org/wiki/Ebers_Papyrus" title="Ebers Papyrus">Ebers Papyrus</a>.</p></div></div></div><h3><span class="mw-headline" id="Hallucinations">Hallucinations</span></h3><p>A <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">hallucination</a> is defined as sensory perception in the absence of external stimuli. Hallucinations are different from <a href="https://en.wikipedia.org/wiki/Illusion" title="Illusion">illusions</a>
and perceptual distortions, which are the misperception of external
stimuli. Hallucinations may occur in any of the senses and take on
almost any form. They may consist of simple sensations (such as lights,
colors, sounds, tastes, or smells) or more detailed experiences (such as
seeing and interacting with animals and people, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Auditory_verbal_hallucinations" title="Auditory verbal hallucinations">hearing voices</a>, and having complex tactile sensations). Hallucinations are generally characterized as being vivid and uncontrollable. <a href="https://en.wikipedia.org/wiki/Auditory_hallucination" title="Auditory hallucination">Auditory hallucinations</a>, particularly experiences of hearing voices, are the most common and often prominent feature of psychosis.
</p><p>Up to 15% of the general population may experience auditory
hallucinations (though not all are due to psychosis). The prevalence of
auditory hallucinations in patients with schizophrenia is generally put
around 70%, but may go as high as 98%. Reported prevalence in bipolar
disorder ranges between 11% and 68%. During the early 20th century, auditory hallucinations were second to <a href="https://en.wikipedia.org/wiki/Visual_hallucinations_in_psychosis" title="Visual hallucinations in psychosis">visual hallucinations</a>
in frequency, but they are now the most common manifestation of
schizophrenia, although rates vary between cultures and regions.
Auditory hallucinations are most commonly intelligible voices. When
voices are present, the average number has been estimated at three.
Content, like frequency, differs significantly, especially across
cultures and demographics. People who experience auditory hallucinations
can frequently identify the loudness, location of origin, and may
settle on identities for voices. Western cultures are associated with
auditory experiences concerning religious content, frequently related to
sin. Hallucinations may command a person to do something potentially
dangerous when combined with delusions.
</p><p>So-called "minor hallucinations", such as extracampine
hallucinations, or false perceptions of people or movement occurring
outside of one's visual field, frequently occur in neurocognitive
disorders, such as Parkinson's disease.
</p><p>Visual hallucinations occur in roughly a third of people with
schizophrenia, although rates as high as 55% are reported. The
prevalence in bipolar disorder is around 15%. Content commonly involves
animate objects, although perceptual abnormalities such as changes in
lighting, shading, streaks, or lines may be seen. Visual abnormalities
may conflict with <a href="https://en.wikipedia.org/wiki/Proprioception" title="Proprioception">proprioceptive</a> information, and visions may include experiences such as the ground tilting. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lilliputian_hallucinations" title="Lilliputian hallucinations">Lilliputian hallucinations</a> are less common in schizophrenia, and are more common in various types of <a href="https://en.wikipedia.org/wiki/Encephalopathy" title="Encephalopathy">encephalopathy</a>, such as <a href="https://en.wikipedia.org/wiki/Peduncular_hallucinosis" title="Peduncular hallucinosis">peduncular hallucinosis</a>.
</p><p>A visceral hallucination, also called a cenesthetic
hallucination, is characterized by visceral sensations in the absence of
stimuli. Cenesthetic hallucinations may include sensations of burning,
or re-arrangement of internal organs.
</p>
<h3><span class="mw-headline" id="Delusions">Delusions</span></h3><p>Psychosis may involve <a href="https://en.wikipedia.org/wiki/Delusion" title="Delusion">delusional</a> beliefs. A delusion is a <i>fixed, false idiosyncratic belief</i>,
which does not change even when presented with incontrovertible
evidence to the contrary. Delusions are context- and culture-dependent: a
belief which inhibits critical functioning and is widely considered
delusional in one population may be common (and even adaptive) in
another, or in the same population at a later time. Since <a href="https://en.wikipedia.org/wiki/Norm_(philosophy)" title="Norm (philosophy)">normative</a> views may contradict available evidence, a belief need not contravene cultural standards in order to be considered delusional.
</p><p>Prevalence in schizophrenia is generally considered at least 90%, and around 50% in bipolar disorder.
</p><p>The DSM-5 characterizes certain delusions as "bizarre" if they
are clearly implausible, or are incompatible with the surrounding
cultural context. The concept of bizarre delusions has many criticisms,
the most prominent being judging its presence is not highly reliable
even among trained individuals.
</p><p>A delusion may involve diverse thematic content. The most common type is a <a href="https://en.wikipedia.org/wiki/Persecutory_delusion" title="Persecutory delusion">persecutory delusion</a>, in which a person believes that an entity seeks to harm them. Others include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Delusions_of_reference" title="Delusions of reference">delusions of reference</a>
(the belief that some element of one's experience represents a
deliberate and specific act by or message from some other entity), <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Delusions_of_grandeur" title="Delusions of grandeur">delusions of grandeur</a> (the belief that one possesses special power or influence beyond one's actual limits), <a href="https://en.wikipedia.org/wiki/Thought_broadcasting" title="Thought broadcasting">thought broadcasting</a> (the belief that one's thoughts are audible) and <a href="https://en.wikipedia.org/wiki/Thought_insertion" title="Thought insertion">thought insertion</a> (the belief that one's thoughts are not one's own). A delusion may also involve <a href="https://en.wikipedia.org/wiki/Delusional_misidentification_syndrome" title="Delusional misidentification syndrome">misidentification</a> of objects, persons, or environs that the afflicted should reasonably be able to recognize; such examples include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cotard_delusion" title="Cotard delusion">Cotard's syndrome</a> (the belief that oneself is partly or wholly <a href="https://en.wikipedia.org/wiki/Death" title="Death">dead</a>) and <a href="https://en.wikipedia.org/wiki/Clinical_lycanthropy" title="Clinical lycanthropy">clinical lycanthropy</a> (the belief that oneself is or has transformed into an animal).
</p><p>The subject matter of delusions seems to reflect the current
culture in a particular time and location. For example, in the US,
during the early 1900s syphilis was a common topic, during the Second
World War Germany, during the Cold War communists, and in recent years,
technology has been a focus. Some psychologists, such as those who practice the <a href="https://en.wikipedia.org/wiki/Open_Dialogue" title="Open Dialogue">Open Dialogue</a>
method, believe that the content of psychosis represents an underlying
thought process that may, in part, be responsible for psychosis, though the accepted medical position is that psychosis is due to a brain disorder.
</p><p>Historically, <a href="https://en.wikipedia.org/wiki/Karl_Jaspers" title="Karl Jaspers">Karl Jaspers</a> classified psychotic delusions into <i>primary</i> and <i>secondary</i>
types. Primary delusions are defined as arising suddenly and not being
comprehensible in terms of normal mental processes, whereas secondary
delusions are typically understood as being influenced by the person's
background or current situation (e.g., ethnicity; also religious,
superstitious, or political beliefs).
</p>
<h3><span id="Disorganization_of_speech.2Fthought_or_behavior"></span><span class="mw-headline" id="Disorganization_of_speech/thought_or_behavior">Disorganization of speech/thought or behavior</span></h3><p>Disorganization
is split into disorganized speech (or thought), and grossly
disorganized motor behavior. Disorganized speech or thought, also called
formal <a href="https://en.wikipedia.org/wiki/Thought_disorder" title="Thought disorder">thought disorder</a>, is disorganization of thinking that is <i>inferred</i>
from speech. Characteristics of disorganized speech include rapidly
switching topics, called derailment or loose association; switching to
topics that are unrelated, called tangential thinking; incomprehensible
speech, called <a href="https://en.wikipedia.org/wiki/Word_salad" title="Word salad">word salad</a>
or incoherence. Disorganized motor behavior includes repetitive, odd,
or sometimes purposeless movement. Disorganized motor behavior rarely
includes catatonia, and although it was a historically prominent
symptom, it is rarely seen today. Whether this is due to historically
used treatments or the lack thereof is unknown.
</p><p><a href="https://en.wikipedia.org/wiki/Catatonia" title="Catatonia">Catatonia</a>
describes a profoundly agitated state in which the experience of
reality is generally considered impaired. There are two primary
manifestations of catatonic behavior. The classic presentation is a
person who does not move or interact with the world in any way while
awake. This type of catatonia presents with <a href="https://en.wikipedia.org/wiki/Waxy_flexibility" title="Waxy flexibility">waxy flexibility</a>.
Waxy flexibility is when someone physically moves part of a catatonic
person's body and the person stays in the position even if it is bizarre
and otherwise nonfunctional (such as moving a person's arm straight up
in the air and the arm staying there).
</p><p>The other type of catatonia is more of an outward presentation of
the profoundly agitated state described above. It involves excessive
and purposeless motor behaviour, as well as an extreme mental
preoccupation that prevents an intact experience of reality. An example
is someone walking very fast in circles to the exclusion of anything
else with a level of mental preoccupation (meaning not focused on
anything relevant to the situation) that was not typical of the person
prior to the symptom onset. In both types of catatonia, there is
generally no reaction to anything that happens outside of them. It is
important to distinguish catatonic agitation from severe bipolar mania,
although someone could have both.
</p>
<h3><span class="mw-headline" id="Negative_symptoms">Negative symptoms</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Clouding_of_consciousness" title="Clouding of consciousness">Clouding of consciousness</a> and <a href="https://en.wikipedia.org/wiki/Depression_(mood)" title="Depression (mood)">Depression (mood)</a></div>
<p>Negative symptoms include reduced emotional expression (<a href="https://en.wikipedia.org/wiki/Reduced_affect_display" title="Reduced affect display">flat affect</a>), <a href="https://en.wikipedia.org/wiki/Avolition" title="Avolition">decreased motivation</a> (<a href="https://en.wikipedia.org/wiki/Avolition" title="Avolition">avolition</a>), and <a href="https://en.wikipedia.org/wiki/Alogia" title="Alogia">reduced spontaneous speech</a> (poverty of speech, <a href="https://en.wikipedia.org/wiki/Alogia" title="Alogia">alogia</a>). Individuals with this condition lack interest and spontaneity, and have the <a href="https://en.wikipedia.org/wiki/Anhedonia" title="Anhedonia">inability to feel pleasure</a> (<a href="https://en.wikipedia.org/wiki/Anhedonia" title="Anhedonia">anhedonia</a>). Altered
Behavioral Inhibition System functioning could possibly cause reduced
sustained attention in psychosis and overall contribute to more negative
reactions.
</p>
<h3><span class="mw-headline" id="Psychosis_in_adolescents">Psychosis in adolescents</span></h3><p>Psychosis is rare in adolescents.
Young people who have psychosis may have trouble connecting with the
world around them and may experience hallucinations and/or delusions. Adolescents with psychosis may also have cognitive deficits that may make it harder for the youth to socialize and work. Potential impairments include the speed of mental processing, ability to focus without getting distracted (limited <a href="https://en.wikipedia.org/wiki/Attention_span" title="Attention span">attention span</a>), and deficits in <a href="https://en.wikipedia.org/wiki/Verbal_memory" title="Verbal memory">verbal memory</a>.
If an adolescent is experiencing psychosis, they most likely have
comorbidity meaning they could have multiple mental illnesses.
Because of this, it can be difficult to determine if it is psychosis or
autism spectrum disorder, social or generalized anxiety disorder, or
obsessive-compulsive disorder.
</p>
<h2><span class="mw-headline" id="Causes">Causes</span></h2><p>The symptoms of psychosis may be caused by serious <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Psychiatric_disorders" title="Psychiatric disorders">psychiatric disorders</a> such as <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a>, a number of medical illnesses, and <a href="https://en.wikipedia.org/wiki/Psychological_trauma" title="Psychological trauma">trauma</a>. Psychosis may also be temporary or transient, and be caused by medications or <a href="https://en.wikipedia.org/wiki/Substance_use_disorder" title="Substance use disorder">substance use disorder</a> (<a href="https://en.wikipedia.org/wiki/Substance-induced_psychosis" title="Substance-induced psychosis">substance-induced psychosis</a>).
</p>
<h3><span class="mw-headline" id="Normal_states">Normal states</span></h3><p>Brief
hallucinations are not uncommon in those without any psychiatric
disease, including healthy children. Causes or triggers include:
</p>
<ul><li>Falling asleep and waking: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypnagogic" title="Hypnagogic">hypnagogic</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypnopompic" title="Hypnopompic">hypnopompic</a> hallucinations</li><li><a href="https://en.wikipedia.org/wiki/Grief" title="Grief">Bereavement</a>, in which hallucinations of a deceased loved one are common</li><li>Severe <a href="https://en.wikipedia.org/wiki/Sleep_deprivation" title="Sleep deprivation">sleep deprivation</a></li><li>Extreme stress (see below)</li></ul>
<h3><span class="mw-headline" id="Trauma_and_stress">Trauma and stress</span></h3><p>Traumatic life events have been linked with an elevated risk of developing psychotic symptoms. Childhood trauma has specifically been shown to be a predictor of adolescent and adult psychosis.
Individuals with psychotic symptoms are three times more likely to have
experienced childhood trauma (e.g., physical or sexual abuse, physical
or emotional neglect) than those in the general population.<sup class="reference" id="cite_ref-:2_34-1"><a href="https://en.wikipedia.org/wiki/Psychosis#cite_note-:2-34">[</a></sup></p><p> Increased individual vulnerability toward psychosis may interact with
traumatic experiences promoting an onset of future psychotic symptoms,
particularly during sensitive developmental periods.
Importantly, the relationship between traumatic life events and
psychotic symptoms appears to be dose-dependent in which multiple
traumatic life events accumulate, compounding symptom expression and
severity. However, acute, stressful events can also trigger brief psychotic episodes.
Trauma prevention and early intervention may be an important target for
decreasing the incidence of psychotic disorders and ameliorating its
effects.
A healthy person could become psychotic if he is placed in an empty
room with no light and sound after 15 minutes, a phenomenon known as <a href="https://en.wikipedia.org/wiki/Sensory_deprivation" title="Sensory deprivation">sensory deprivation</a>.
</p><p><a href="https://en.wikipedia.org/wiki/Neuroticism" title="Neuroticism">Neuroticism</a>, a personality trait associated with vulnerability to stressors, is an independent predictor of the development of psychosis.
</p>
<h3><span class="mw-headline" id="Psychiatric_disorders">Psychiatric disorders</span></h3><p>From
a diagnostic standpoint, organic disorders were believed to be caused
by physical illness affecting the brain (that is, psychiatric disorders
secondary to other conditions) while functional disorders were
considered disorders of the functioning of the mind in the absence of
physical disorders (that is, primary psychological or psychiatric
disorders). Subtle physical abnormalities have been found in illnesses
traditionally considered functional, such as <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a>. The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/DSM-IV-TR" title="DSM-IV-TR">DSM-IV-TR</a>
avoids the functional/organic distinction, and instead lists
traditional psychotic illnesses, psychosis due to general medical
conditions, and substance-induced psychosis.
</p><p>Primary psychiatric causes of psychosis include the following:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mood_disorders" title="Mood disorders">mood disorders</a>, including <a href="https://en.wikipedia.org/wiki/Psychotic_depression" title="Psychotic depression">psychotic depression</a> and <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a> in the <a href="https://en.wikipedia.org/wiki/Mania" title="Mania">manic</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mixed_episode" title="Mixed episode">mixed episodes</a> of <a href="https://en.wikipedia.org/wiki/Bipolar_I_disorder" title="Bipolar I disorder">bipolar I disorder</a> and depressive episodes of both <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bipolar_I" title="Bipolar I">bipolar I</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bipolar_II" title="Bipolar II">bipolar II</a></li><li><a href="https://en.wikipedia.org/wiki/Schizoaffective_disorder" title="Schizoaffective disorder">schizoaffective disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Delusional_disorder" title="Delusional disorder">delusional disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Brief_psychotic_disorder" title="Brief psychotic disorder">brief psychotic disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Schizophreniform_disorder" title="Schizophreniform disorder">schizophreniform disorder</a></li></ul>
<p>Psychotic symptoms may also be seen in:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Schizotypal_personality_disorder" title="Schizotypal personality disorder">Schizotypal personality disorder</a></li><li>Certain <a href="https://en.wikipedia.org/wiki/Personality_disorder" title="Personality disorder">personality disorders</a> in times of stress (including <a href="https://en.wikipedia.org/wiki/Paranoid_personality_disorder" title="Paranoid personality disorder">paranoid personality disorder</a>, <a href="https://en.wikipedia.org/wiki/Schizoid_personality_disorder" title="Schizoid personality disorder">schizoid personality disorder</a>, and <a href="https://en.wikipedia.org/wiki/Borderline_personality_disorder" title="Borderline personality disorder">borderline personality disorder</a>)</li><li><a href="https://en.wikipedia.org/wiki/Post-traumatic_stress_disorder" title="Post-traumatic stress disorder">Post-traumatic stress disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Folie_%C3%A0_deux" title="Folie à deux">Shared delusional disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Obsessive%E2%80%93compulsive_disorder" title="Obsessive–compulsive disorder">obsessive–compulsive disorder</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dissociative_disorder" title="Dissociative disorder">Dissociative disorders</a>, due to many overlapping symptoms, especially <a href="https://en.wikipedia.org/wiki/Dissociative_identity_disorder" title="Dissociative identity disorder">dissociative identity disorder</a>.</li></ul>
<h4><span class="mw-headline" id="Subtypes">Subtypes</span></h4><p>Subtypes of psychosis include:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Postpartum_psychosis" title="Postpartum psychosis">Postpartum psychosis</a>, occurring shortly after <a href="https://en.wikipedia.org/wiki/Childbirth" title="Childbirth">giving birth</a>, primarily associated with maternal <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a></li><li><a href="https://en.wikipedia.org/wiki/Monothematic_delusion" title="Monothematic delusion">Monothematic delusions</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Myxedematous_psychosis" title="Myxedematous psychosis">Myxedematous psychosis</a></li><li><a href="https://en.wikipedia.org/wiki/Stimulant_psychosis" title="Stimulant psychosis">Stimulant psychosis</a></li><li><a href="https://en.wikipedia.org/wiki/Tardive_psychosis" title="Tardive psychosis">Tardive psychosis</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Shared_psychosis" title="Shared psychosis">Shared psychosis</a> (<i>folie à deux</i>)</li></ul>
<h4><span class="mw-headline" id="Cycloid_psychosis">Cycloid psychosis</span></h4><p>Cycloid
psychosis is typically an acute, self-limiting form of psychosis with
psychotic and mood symptoms that progress from normal to full-blown,
usually between a few hours to days, and not related to drug intake or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Brain_injury" title="Brain injury">brain injury</a>.
While proposed as a distinct entity, clinically separate from
schizophrenia and affective disorders, cycloid psychosis is not formally
acknowledged by current ICD or DSM criteria.
Its unclear place in psychiatric nosology has likely contributed to the
limited scientific investigation and literature on the topic.
</p>
<h4><span class="mw-headline" id="Postpartum_psychosis">Postpartum psychosis</span></h4><p><a href="https://en.wikipedia.org/wiki/Postpartum_psychosis" title="Postpartum psychosis">Postpartum psychosis</a> is a rare yet serious and debilitating form of psychosis. Symptoms range from fluctuating moods and insomnia to mood-incongruent delusions related to the individual or the infant.
Women experiencing postpartum psychosis are at increased risk for
suicide or infanticide. Many women who experience first-time psychosis
from postpartum often have bipolar disorder, meaning they could
experience an increase of psychotic episodes even after postpartum.
</p>
<h3><span class="mw-headline" id="Medical_conditions">Medical conditions</span></h3><p>A very large number of medical conditions can cause psychosis, sometimes called <i>secondary psychosis</i>. Examples include:
</p>
<ul><li>disorders causing <i><a href="https://en.wikipedia.org/wiki/Delirium" title="Delirium">delirium</a></i> (<i>toxic psychosis</i>), in which consciousness is disturbed</li><li>neurodevelopmental disorders and chromosomal abnormalities, including <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Velocardiofacial_syndrome" title="Velocardiofacial syndrome">velocardiofacial syndrome</a></li><li>neurodegenerative disorders, such as <a href="https://en.wikipedia.org/wiki/Alzheimer%27s_disease" title="Alzheimer's disease">Alzheimer's disease</a>, <a href="https://en.wikipedia.org/wiki/Dementia_with_Lewy_bodies" title="Dementia with Lewy bodies">dementia with Lewy bodies</a>, and <a href="https://en.wikipedia.org/wiki/Parkinson%27s_disease" title="Parkinson's disease">Parkinson's disease</a></li><li>focal neurological disease, such as <a href="https://en.wikipedia.org/wiki/Stroke" title="Stroke">stroke</a>, <a href="https://en.wikipedia.org/wiki/Brain_tumor" title="Brain tumor">brain tumors</a>, <a href="https://en.wikipedia.org/wiki/Multiple_sclerosis" title="Multiple sclerosis">multiple sclerosis</a>, and some forms of <a href="https://en.wikipedia.org/wiki/Epilepsy" title="Epilepsy">epilepsy</a></li><li>malignancy (typically via masses in the brain, <a href="https://en.wikipedia.org/wiki/Paraneoplastic_syndrome" title="Paraneoplastic syndrome">paraneoplastic syndromes</a>)</li><li>infectious and postinfectious syndromes, including infections causing <a href="https://en.wikipedia.org/wiki/Delirium" title="Delirium">delirium</a>, <a href="https://en.wikipedia.org/wiki/Viral_encephalitis" title="Viral encephalitis">viral encephalitis</a>, <a href="https://en.wikipedia.org/wiki/HIV/AIDS" title="HIV/AIDS">HIV/AIDS</a>, <a href="https://en.wikipedia.org/wiki/Malaria" title="Malaria">malaria</a>, <a href="https://en.wikipedia.org/wiki/Syphilis" title="Syphilis">syphilis</a></li><li>endocrine disease, such as <a href="https://en.wikipedia.org/wiki/Hypothyroidism" title="Hypothyroidism">hypothyroidism</a>, <a href="https://en.wikipedia.org/wiki/Hyperthyroidism" title="Hyperthyroidism">hyperthyroidism</a>, <a href="https://en.wikipedia.org/wiki/Cushing%27s_syndrome" title="Cushing's syndrome">Cushing's syndrome</a>, <a href="https://en.wikipedia.org/wiki/Hypoparathyroidism" title="Hypoparathyroidism">hypoparathyroidism</a> and <a href="https://en.wikipedia.org/wiki/Hyperparathyroidism" title="Hyperparathyroidism">hyperparathyroidism</a>; sex hormones also affect psychotic symptoms and sometimes giving birth can provoke psychosis, termed <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Puerperal_psychosis" title="Puerperal psychosis">postpartum psychosis</a></li><li>inborn errors of metabolism, such as Wilson's disease, porphyria, and homocysteinemia.</li><li>nutritional deficiency, such as <a href="https://en.wikipedia.org/wiki/Vitamin_B12_deficiency" title="Vitamin B12 deficiency">vitamin B<sub>12</sub> deficiency</a></li><li>other acquired metabolic disorders, including <a href="https://en.wikipedia.org/wiki/Electrolyte" title="Electrolyte">electrolyte</a> disturbances such as <a href="https://en.wikipedia.org/wiki/Hypocalcemia" title="Hypocalcemia">hypocalcemia</a>, <a href="https://en.wikipedia.org/wiki/Hypernatremia" title="Hypernatremia">hypernatremia</a>, <a href="https://en.wikipedia.org/wiki/Hyponatremia" title="Hyponatremia">hyponatremia</a>, <a href="https://en.wikipedia.org/wiki/Hypokalemia" title="Hypokalemia">hypokalemia</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypomagnesemia" title="Hypomagnesemia">hypomagnesemia</a>, <a href="https://en.wikipedia.org/wiki/Hypermagnesemia" title="Hypermagnesemia">hypermagnesemia</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypercalcemia" title="Hypercalcemia">hypercalcemia</a>, and <a href="https://en.wikipedia.org/wiki/Hypophosphatemia" title="Hypophosphatemia">hypophosphatemia</a>, but also <a href="https://en.wikipedia.org/wiki/Hypoglycemia" title="Hypoglycemia">hypoglycemia</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypoxia_(medical)" title="Hypoxia (medical)">hypoxia</a>, and failure of the <a href="https://en.wikipedia.org/wiki/Liver" title="Liver">liver</a> or <a href="https://en.wikipedia.org/wiki/Kidney" title="Kidney">kidneys</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Autoimmune" title="Autoimmune">autoimmune</a> and related disorders, such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Systemic_lupus_erythematosus" title="Systemic lupus erythematosus">systemic lupus erythematosus</a> (lupus, SLE), <a href="https://en.wikipedia.org/wiki/Sarcoidosis" title="Sarcoidosis">sarcoidosis</a>, <a href="https://en.wikipedia.org/wiki/Hashimoto%27s_encephalopathy" title="Hashimoto's encephalopathy">Hashimoto's encephalopathy</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Anti-NMDA-receptor_encephalitis" title="Anti-NMDA-receptor encephalitis">anti-NMDA-receptor encephalitis</a>, and <a href="https://en.wikipedia.org/wiki/Non-celiac_gluten_sensitivity" title="Non-celiac gluten sensitivity">non-celiac gluten sensitivity</a></li><li>poisoning by a range of plants, fungi, metals, organic compounds, and a few animal toxins</li><li>sleep disorders, such as in <a href="https://en.wikipedia.org/wiki/Narcolepsy" title="Narcolepsy">narcolepsy</a> (in which <a class="mw-redirect" href="https://en.wikipedia.org/wiki/REM_sleep" title="REM sleep">REM sleep</a> intrudes into wakefulness)</li><li>parasitic diseases, such as <a href="https://en.wikipedia.org/wiki/Neurocysticercosis" title="Neurocysticercosis">neurocysticercosis</a></li></ul>
<h3><span class="mw-headline" id="Psychoactive_drugs">Psychoactive drugs</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Substance-induced_psychosis" title="Substance-induced psychosis">Substance-induced psychosis</a></div>
<p>Various <a href="https://en.wikipedia.org/wiki/Psychoactive_drug" title="Psychoactive drug">psychoactive substances</a>
(both legal and illegal) have been implicated in causing, exacerbating,
or precipitating psychotic states or disorders in users, with varying
levels of evidence. This may be upon intoxication for a more prolonged
period after use, or upon <a href="https://en.wikipedia.org/wiki/Drug_withdrawal" title="Drug withdrawal">withdrawal</a>.
Individuals who experience substance-induced psychosis tend to have a
greater awareness of their psychosis and tend to have higher levels of <a href="https://en.wikipedia.org/wiki/Suicidal_ideation" title="Suicidal ideation">suicidal thinking</a> compared to those who have a primary psychotic illness. Drugs commonly alleged to induce psychotic symptoms include <a href="https://en.wikipedia.org/wiki/Alcohol_(drug)" title="Alcohol (drug)">alcohol</a>, <a href="https://en.wikipedia.org/wiki/Cannabis_(drug)" title="Cannabis (drug)">cannabis</a>, <a href="https://en.wikipedia.org/wiki/Cocaine" title="Cocaine">cocaine</a>, <a href="https://en.wikipedia.org/wiki/Amphetamine" title="Amphetamine">amphetamines</a>, <a href="https://en.wikipedia.org/wiki/Cathinone" title="Cathinone">cathinones</a>, <a href="https://en.wikipedia.org/wiki/Psychedelic_drug" title="Psychedelic drug">psychedelic drugs</a> (such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lysergic_acid_diethylamide" title="Lysergic acid diethylamide">LSD</a> and <a href="https://en.wikipedia.org/wiki/Psilocybin" title="Psilocybin">psilocybin</a>), <a href="https://en.wikipedia.org/wiki/%CE%9A-opioid_receptor" title="Κ-opioid receptor">κ-opioid receptor</a> <a href="https://en.wikipedia.org/wiki/Agonist" title="Agonist">agonists</a> (such as <a href="https://en.wikipedia.org/wiki/Enadoline" title="Enadoline">enadoline</a> and <a href="https://en.wikipedia.org/wiki/Salvinorin_A" title="Salvinorin A">salvinorin A</a>) and <a href="https://en.wikipedia.org/wiki/NMDA_receptor_antagonist" title="NMDA receptor antagonist">NMDA receptor antagonists</a> (such as <a href="https://en.wikipedia.org/wiki/Phencyclidine" title="Phencyclidine">phencyclidine</a> and <a href="https://en.wikipedia.org/wiki/Ketamine" title="Ketamine">ketamine</a>). <a href="https://en.wikipedia.org/wiki/Caffeine" title="Caffeine">Caffeine</a> may worsen symptoms in those with schizophrenia and cause psychosis at very high doses in people without the condition. Cannabis and other illicit recreational drugs are often associated with
psychosis in adolescents and cannabis use before 15 years old may
increase the risk of psychosis in adulthood.
</p>
<h4><span class="mw-headline" id="Alcohol">Alcohol</span></h4><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Long-term_effects_of_alcohol_consumption#Mental_health_effects" title="Long-term effects of alcohol consumption">Long-term effects of alcohol consumption § Mental health effects</a></div>
<p>Approximately three percent of people with <a href="https://en.wikipedia.org/wiki/Alcoholism" title="Alcoholism">alcoholism</a> experience psychosis during acute intoxication or withdrawal. Alcohol related psychosis may manifest itself through a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Kindling_(sedative-hypnotic_withdrawal)" title="Kindling (sedative-hypnotic withdrawal)">kindling mechanism</a>. The mechanism of alcohol-related psychosis is due to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Long-term_effects_of_alcohol_consumption" title="Long-term effects of alcohol consumption">long-term effects of alcohol consumption</a> resulting in distortions to neuronal membranes, <a href="https://en.wikipedia.org/wiki/Gene_expression" title="Gene expression">gene expression</a>, as well as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Thiamin" title="Thiamin">thiamin</a>
deficiency. It is possible that hazardous alcohol use via a kindling
mechanism can cause the development of a chronic substance-induced
psychotic disorder, i.e. schizophrenia. The effects of an
alcohol-related psychosis include an increased risk of depression and
suicide as well as causing psychosocial impairments. <a href="https://en.wikipedia.org/wiki/Delirium_tremens" title="Delirium tremens">Delirium tremens</a>,
a symptom of chronic alcoholism which can appear in the acute
withdrawal phase, shares many symptoms with alcohol-related psychosis
suggesting a common mechanism.
</p>
<h4><span class="mw-headline" id="Cannabis">Cannabis</span></h4><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Causes_of_schizophrenia#Cannabis" title="Causes of schizophrenia">Causes of schizophrenia § Cannabis</a>, and <a href="https://en.wikipedia.org/wiki/Long-term_effects_of_cannabis#Chronic_psychosis_and_schizophrenia_spectrum_disorders" title="Long-term effects of cannabis">Long-term effects of cannabis § Chronic psychosis and schizophrenia spectrum disorders</a></div>
<p>According to current studies, cannabis use is associated with
increased risk of psychotic disorders, and the more often cannabis is
used the more likely a person is to develop a psychotic illness. Furthermore, people with a history of cannabis use develop psychotic symptoms earlier than those who have never used cannabis.
Some debate exists regarding the causal relationship between cannabis
use and psychosis with some studies suggesting that cannabis use hastens
the onset of psychosis primarily in those with pre-existing
vulnerability.
Indeed, cannabis use plays an important role in the development of
psychosis in vulnerable individuals, and cannabis use in adolescence
should be discouraged. Some studies indicate that the effects of two active compounds in cannabis, <a href="https://en.wikipedia.org/wiki/Tetrahydrocannabinol" title="Tetrahydrocannabinol">tetrahydrocannabinol</a> (THC) and <a href="https://en.wikipedia.org/wiki/Cannabidiol" title="Cannabidiol">cannabidiol</a>
(CBD), have opposite effects with respect to psychosis. While THC can
induce psychotic symptoms in healthy individuals, limited evidence
suggests that CBD may have antipsychotic effects.
</p>
<h4><span class="mw-headline" id="Methamphetamine">Methamphetamine</span></h4><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Stimulant_psychosis" title="Stimulant psychosis">Stimulant psychosis</a></div>
<p><a href="https://en.wikipedia.org/wiki/Methamphetamine" title="Methamphetamine">Methamphetamine</a>
induces a psychosis in 26–46 percent of heavy users. Some of these
people develop a long-lasting psychosis that can persist for longer than
six months. Those who have had a short-lived psychosis from
methamphetamine can have a relapse of the methamphetamine psychosis
years later after a stressful event such as severe insomnia or a period
of hazardous alcohol use despite not relapsing back to methamphetamine.
Individuals who have a long history of methamphetamine use and who have
experienced psychosis in the past from methamphetamine use are highly
likely to re-experience methamphetamine psychosis if drug use is
recommenced. Methamphetamine-induced psychosis is likely gated by
genetic vulnerability, which can produce long-term changes in brain
neurochemistry following repetitive use.
</p>
<h3><span class="mw-headline" id="Medication">Medication</span></h3><p>Administration, or sometimes withdrawal, of a large number of medications may provoke psychotic symptoms. Drugs that can induce psychosis experimentally or in a significant proportion of people include:
</p>
<ul><li>Stimulants, such as <a href="https://en.wikipedia.org/wiki/Amphetamine" title="Amphetamine">amphetamine</a> and other <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sympathomimetics" title="Sympathomimetics">sympathomimetics</a>,</li><li><a href="https://en.wikipedia.org/wiki/Dopamine" title="Dopamine">dopamine</a> agonists,</li><li><a href="https://en.wikipedia.org/wiki/Ketamine" title="Ketamine">ketamine</a>,</li><li><a href="https://en.wikipedia.org/wiki/Corticosteroid" title="Corticosteroid">corticosteroids</a> (often with mood changes in addition),</li><li><a class="external text" href="https://pubmed.ncbi.nlm.nih.gov/35747110/" rel="nofollow">Ivermectin</a></li><li>and some anticonvulsants such as <a href="https://en.wikipedia.org/wiki/Vigabatrin" title="Vigabatrin">vigabatrin</a>.</li></ul>
<h2><span class="mw-headline" id="Pathophysiology">Pathophysiology</span></h2><h3><span class="mw-headline" id="Neuroimaging">Neuroimaging</span></h3><p>The first brain image of an individual with psychosis was completed as far back as 1935 using a technique called <a href="https://en.wikipedia.org/wiki/Pneumoencephalography" title="Pneumoencephalography">pneumoencephalography</a> (a painful and now obsolete procedure where <a href="https://en.wikipedia.org/wiki/Cerebrospinal_fluid" title="Cerebrospinal fluid">cerebrospinal fluid</a> is drained from around the brain and replaced with air to allow the structure of the brain to show up more clearly on an <a href="https://en.wikipedia.org/wiki/X-ray" title="X-ray">X-ray</a> picture).
</p><p>Both <a href="https://en.wikipedia.org/wiki/Antipsychotic#First_episode_psychosis" title="Antipsychotic">first episode psychosis</a>,
and high risk status is associated with reductions in grey matter
volume (GMV). First episode psychotic and high risk populations are
associated with similar but distinct abnormalities in GMV. Reductions in
the right <a href="https://en.wikipedia.org/wiki/Middle_temporal_gyrus" title="Middle temporal gyrus">middle temporal gyrus</a>, right <a href="https://en.wikipedia.org/wiki/Superior_temporal_gyrus" title="Superior temporal gyrus">superior temporal gyrus</a> (STG), right <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Parahippocampus" title="Parahippocampus">parahippocampus</a>, right <a href="https://en.wikipedia.org/wiki/Hippocampus" title="Hippocampus">hippocampus</a>, right <a href="https://en.wikipedia.org/wiki/Middle_frontal_gyrus" title="Middle frontal gyrus">middle frontal gyrus</a>, and left <a href="https://en.wikipedia.org/wiki/Anterior_cingulate_cortex" title="Anterior cingulate cortex">anterior cingulate cortex</a>
(ACC) are observed in high risk populations. Reductions in first
episode psychosis span a region from the right STG to the right insula,
left insula, and cerebellum, and are more severe in the right ACC, right
STG, insula and cerebellum.
</p><p>Another meta analysis reported bilateral reductions in insula,
operculum, STG, medial frontal cortex, and ACC, but also reported
increased GMV in the right <a href="https://en.wikipedia.org/wiki/Lingual_gyrus" title="Lingual gyrus">lingual gyrus</a> and left <a href="https://en.wikipedia.org/wiki/Precentral_gyrus" title="Precentral gyrus">precentral gyrus</a>. The <a href="https://en.wikipedia.org/wiki/Kraepelinian_dichotomy" title="Kraepelinian dichotomy">Kraepelinian dichotomy</a> is made questionable
by grey matter abnormalities in bipolar and schizophrenia;
schizophrenia is distinguishable from bipolar in that regions of grey
matter reduction are generally larger in magnitude, although adjusting
for gender differences reduces the difference to the left <a href="https://en.wikipedia.org/wiki/Dorsomedial_prefrontal_cortex" title="Dorsomedial prefrontal cortex">dorsomedial prefrontal cortex</a>, and right <a href="https://en.wikipedia.org/wiki/Dorsolateral_prefrontal_cortex" title="Dorsolateral prefrontal cortex">dorsolateral prefrontal cortex</a>.
</p><p>During attentional tasks, first episode psychosis is associated
with hypoactivation in the right middle frontal gyrus, a region
generally described as encompassing the dorsolateral prefrontal cortex
(dlPFC). In congruence with studies on grey matter volume, hypoactivity
in the right insula, and right inferior parietal lobe is also reported.
During cognitive tasks, hypoactivities in the right insula, dACC, and
the left precuneus, as well as reduced deactivations in the right <a href="https://en.wikipedia.org/wiki/Basal_ganglia" title="Basal ganglia">basal ganglia</a>, right <a href="https://en.wikipedia.org/wiki/Thalamus" title="Thalamus">thalamus</a>, right <a href="https://en.wikipedia.org/wiki/Inferior_frontal_gyrus" title="Inferior frontal gyrus">inferior frontal</a>
and left precentral gyri are observed. These results are highly
consistent and replicable possibly except the abnormalities of the right
inferior frontal gyrus.
Decreased grey matter volume in conjunction with bilateral hypoactivity
is observed in anterior insula, dorsal medial frontal cortex, and
dorsal ACC. Decreased grey matter volume and bilateral hyperactivity is
reported in posterior insula, ventral medial frontal cortex, and ventral
ACC.
</p>
<h3><span class="mw-headline" id="Hallucinations_2">Hallucinations</span></h3><p>Studies
during acute experiences of hallucinations demonstrate increased
activity in primary or secondary sensory cortices. As auditory
hallucinations are most common in psychosis, most robust evidence exists
for increased activity in the left <a href="https://en.wikipedia.org/wiki/Middle_temporal_gyrus" title="Middle temporal gyrus">middle temporal gyrus</a>, left <a href="https://en.wikipedia.org/wiki/Superior_temporal_gyrus" title="Superior temporal gyrus">superior temporal gyrus</a>, and left <a href="https://en.wikipedia.org/wiki/Inferior_frontal_gyrus" title="Inferior frontal gyrus">inferior frontal gyrus</a> (i.e. <a href="https://en.wikipedia.org/wiki/Broca%27s_area" title="Broca's area">Broca's area</a>). Activity in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ventral_striatum" title="Ventral striatum">ventral striatum</a>, <a href="https://en.wikipedia.org/wiki/Hippocampus" title="Hippocampus">hippocampus</a>,
and ACC are related to the lucidity of hallucinations, and indicate
that activation or involvement of emotional circuitry are key to the
impact of abnormal activity in sensory cortices. Together, these
findings indicate abnormal processing of internally generated sensory
experiences, coupled with abnormal emotional processing, results in
hallucinations. One proposed model involves a failure of feedforward
networks from sensory cortices to the inferior frontal cortex, which
normally cancel out sensory cortex activity during internally generated
speech. The resulting disruption in expected and perceived speech is
thought to produce lucid hallucinatory experiences.
</p>
<h3><span class="mw-headline" id="Delusions_2">Delusions</span></h3><p>The
two-factor model of delusions posits that dysfunction in both belief
formation systems and belief evaluation systems are necessary for
delusions. Dysfunction in evaluations systems localized to the right
lateral prefrontal cortex, regardless of delusion content, is supported
by neuroimaging studies and is congruent with its role in conflict
monitoring in healthy persons. Abnormal activation and reduced volume is
seen in people with delusions, as well as in disorders associated with
delusions such as <a href="https://en.wikipedia.org/wiki/Frontotemporal_dementia" title="Frontotemporal dementia">frontotemporal dementia</a>, psychosis and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lewy_body_dementia" title="Lewy body dementia">Lewy body dementia</a>.
Furthermore, lesions to this region are associated with "jumping to
conclusions", damage to this region is associated with post-stroke
delusions, and hypometabolism this region associated with caudate
strokes presenting with delusions.
</p><p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Aberrant_salience" title="Aberrant salience">aberrant salience model</a>
suggests that delusions are a result of people assigning excessive
importance to irrelevant stimuli. In support of this hypothesis, regions
normally associated with the <a href="https://en.wikipedia.org/wiki/Salience_network" title="Salience network">salience network</a> demonstrate reduced grey matter in people with delusions, and the neurotransmitter <a href="https://en.wikipedia.org/wiki/Dopamine" title="Dopamine">dopamine</a>, which is widely implicated in salience processing, is also widely implicated in psychotic disorders.
</p><p>Specific regions have been associated with specific types of
delusions. The volume of the hippocampus and parahippocampus is related
to paranoid delusions in <a href="https://en.wikipedia.org/wiki/Alzheimer%27s_disease" title="Alzheimer's disease">Alzheimer's disease</a>, and has been reported to be abnormal post mortem in one person with delusions. <a href="https://en.wikipedia.org/wiki/Capgras_delusion" title="Capgras delusion">Capgras delusions</a>
have been associated with occipito-temporal damage, and may be related
to failure to elicit normal emotions or memories in response to faces.
</p>
<h3><span class="mw-headline" id="Negative_symptoms_2">Negative symptoms</span></h3>
<p>Psychosis is associated with <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ventral_striatum" title="Ventral striatum">ventral striatal</a> (VS) which is the part of the brain that is involved with the desire to naturally satisfy the body's needs. When high reports of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Symptom#Negative_symptoms" title="Symptom">negative symptoms</a>
were recorded, there were significant irregularities in the left VS.
Anhedonia, the inability to feel pleasure, is a commonly reported
symptom in psychosis; experiences are present in most people with
schizophrenia.
Anhedonia arises as a result of the inability to feel motivation and
drive towards both the desire to engage in as well as to complete tasks
and goals. Previous research has indicated that a deficiency in the <a href="https://en.wikipedia.org/wiki/Neural_coding" title="Neural coding">neural representation</a>
in regards to goals and the motivation to achieve them, has
demonstrated that when a reward is not present, a strong reaction is
noted in the ventral striatum; reinforcement learning is intact when
contingencies about stimulus-reward are implicit, but not when they
require explicit neural processing; reward prediction errors are what
the actual reward is versus what the reward was predicted to be.
In most cases positive prediction errors are considered an abnormal
occurrence. A positive prediction error response occurs when there is an
increased activation in a brain region, typically the <a href="https://en.wikipedia.org/wiki/Striatum" title="Striatum">striatum</a>,
in response to unexpected rewards. A negative prediction error response
occurs when there is a decreased activation in a region when predicted
rewards do not occur. <a href="https://en.wikipedia.org/wiki/Anterior_cingulate_cortex" title="Anterior cingulate cortex">Anterior Cingulate Cortex (ACC)</a>
response, taken as an indicator of effort allocation, does not increase
with reward or reward probability increase, and is associated with
negative symptoms; deficits in <a href="https://en.wikipedia.org/wiki/Dorsolateral_prefrontal_cortex" title="Dorsolateral prefrontal cortex">Dorsolateral Prefrontal Cortex (dlPFC)</a>
activity and failure to improve performance on cognitive tasks when
offered monetary incentives are present; and dopamine mediated functions
are abnormal.
</p>
<h3><span class="mw-headline" id="Neurobiology">Neurobiology</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Dopamine_hypothesis_of_schizophrenia" title="Dopamine hypothesis of schizophrenia">Dopamine hypothesis of schizophrenia</a></div>
<p>Psychosis has been traditionally linked to the overactivity of the <a href="https://en.wikipedia.org/wiki/Neurotransmitter" title="Neurotransmitter">neurotransmitter</a> <a href="https://en.wikipedia.org/wiki/Dopamine" title="Dopamine">dopamine</a>. In particular to its effect in the <a href="https://en.wikipedia.org/wiki/Mesolimbic_pathway" title="Mesolimbic pathway">mesolimbic pathway</a>. The two major sources of evidence given to support this theory are that <a href="https://en.wikipedia.org/wiki/Dopamine_receptor_D2" title="Dopamine receptor D2">dopamine receptor D2</a> blocking drugs (i.e., <a href="https://en.wikipedia.org/wiki/Antipsychotic" title="Antipsychotic">antipsychotics</a>)
tend to reduce the intensity of psychotic symptoms, and that drugs that
accentuate dopamine release, or inhibit its reuptake (such as <a href="https://en.wikipedia.org/wiki/Amphetamine" title="Amphetamine">amphetamines</a> and <a href="https://en.wikipedia.org/wiki/Cocaine" title="Cocaine">cocaine</a>) can trigger psychosis in some people (see <a href="https://en.wikipedia.org/wiki/Stimulant_psychosis" title="Stimulant psychosis">stimulant psychosis</a>).
</p><p>NMDA receptor dysfunction has been proposed as a mechanism in psychosis. This theory is reinforced by the fact that <a href="https://en.wikipedia.org/wiki/Dissociative" title="Dissociative">dissociative</a> <a href="https://en.wikipedia.org/wiki/NMDA_receptor_antagonist" title="NMDA receptor antagonist">NMDA receptor antagonists</a> such as <a href="https://en.wikipedia.org/wiki/Ketamine" title="Ketamine">ketamine</a>, <a href="https://en.wikipedia.org/wiki/Phencyclidine" title="Phencyclidine">PCP</a> and <a href="https://en.wikipedia.org/wiki/Dextromethorphan" title="Dextromethorphan">dextromethorphan</a> (at large overdoses) induce a psychotic state. The symptoms of dissociative <a href="https://en.wikipedia.org/wiki/Substance_intoxication" title="Substance intoxication">intoxication</a> are also considered to mirror the symptoms of schizophrenia, including <a href="https://en.wikipedia.org/wiki/Schizophrenia#Negative_symptoms" title="Schizophrenia">negative symptoms</a>.
NMDA receptor antagonism, in addition to producing symptoms
reminiscent of psychosis, mimics the neurophysiological aspects, such as
reduction in the amplitude of <a href="https://en.wikipedia.org/wiki/P50_(neuroscience)" title="P50 (neuroscience)">P50</a>, <a href="https://en.wikipedia.org/wiki/P300_(neuroscience)" title="P300 (neuroscience)">P300</a>, and <a href="https://en.wikipedia.org/wiki/Mismatch_negativity" title="Mismatch negativity">MMN</a> <a href="https://en.wikipedia.org/wiki/Evoked_potential" title="Evoked potential">evoked potentials</a>.
Hierarchical Bayesian neurocomputational models of sensory feedback, in
agreement with neuroimaging literature, link NMDA receptor hypofunction
to delusional or hallucinatory symptoms via proposing a failure of NMDA
mediated top down predictions to adequately cancel out enhanced bottom
up AMPA mediated predictions errors.
Excessive prediction errors in response to stimuli that would normally
not produce such a response is thought to root from conferring excessive
salience to otherwise mundane events. Dysfunction higher up in the hierarchy, where representation is more abstract, could result in delusions. The common finding of reduced <a class="mw-redirect" href="https://en.wikipedia.org/wiki/GAD67" title="GAD67">GAD67</a> expression in psychotic disorders may explain enhanced AMPA mediated signaling, caused by reduced GABAergic inhibition.
</p><p>The connection between dopamine and psychosis is generally believed to be complex. While dopamine receptor D2 suppresses <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Adenylate_cyclase" title="Adenylate cyclase">adenylate cyclase</a> activity, the <a href="https://en.wikipedia.org/wiki/Dopamine_receptor_D1" title="Dopamine receptor D1">D1</a>
receptor increases it. If D2-blocking drugs are administered, the
blocked dopamine spills over to the D1 receptors. The increased
adenylate cyclase activity affects <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genetic_expression" title="Genetic expression">genetic expression</a>
in the nerve cell, which takes time. Hence antipsychotic drugs take a
week or two to reduce the symptoms of psychosis. Moreover, newer and
equally effective antipsychotic drugs actually block slightly less
dopamine in the brain than older drugs whilst also blocking 5-HT2A
receptors, suggesting the 'dopamine hypothesis' may be oversimplified. Soyka and colleagues found no evidence of dopaminergic dysfunction in people with alcohol-induced psychosis and Zoldan et al. reported moderately successful use of <a href="https://en.wikipedia.org/wiki/Ondansetron" title="Ondansetron">ondansetron</a>, a 5-HT<sub>3</sub> receptor antagonist, in the treatment of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Levodopa" title="Levodopa">levodopa</a> psychosis in <a href="https://en.wikipedia.org/wiki/Parkinson%27s_disease" title="Parkinson's disease">Parkinson's disease</a> patients.
</p><p>A review found an association between a first-episode of psychosis and prediabetes.
</p><p>Prolonged or high dose use of <a href="https://en.wikipedia.org/wiki/Stimulant" title="Stimulant">psychostimulants</a> can alter normal functioning, making it similar to the manic phase of bipolar disorder. NMDA antagonists replicate some of the so-called "negative" symptoms like <a href="https://en.wikipedia.org/wiki/Thought_disorder" title="Thought disorder">thought disorder</a> in subanesthetic doses (doses insufficient to induce <a href="https://en.wikipedia.org/wiki/Anesthesia" title="Anesthesia">anesthesia</a>), and <a href="https://en.wikipedia.org/wiki/Catatonia" title="Catatonia">catatonia</a>
in high doses. Psychostimulants, especially in one already prone to
psychotic thinking, can cause some "positive" symptoms, such as
delusional beliefs, particularly those persecutory in nature.
</p>
<h3><span class="mw-headline" id="Culture">Culture</span></h3><p>Cross-cultural
studies into schizophrenia have found that individual experiences of
psychosis and 'hearing voices' vary across cultures. In countries such as the <a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a>
where there exists a predominantly biomedical understanding of the
body, the mind and in turn, mental health, subjects were found to report
their hallucinations as having 'violent content' and self-describing as
'crazy'. This lived experience is at odds with the lived experience of subjects in <a href="https://en.wikipedia.org/wiki/Accra" title="Accra">Accra, Ghana</a>, who describe the voices they hear as having 'spiritual meaning' and are often reported as positive in nature; or subjects in <a href="https://en.wikipedia.org/wiki/Chennai" title="Chennai">Chennai, India</a>, who describe their hallucinations as kin, family members or close friends, and offering guidance.
</p><p>These differences are attributed to 'social kindling' or how
one's social context shapes how an individual interprets and experiences
sensations such as hallucinations. This concept aligns with
pre-existing cognitive theory such as reality modelling and is supported
by recent research that demonstrates that individuals with psychosis
can be taught to attend to their hallucinations differently, which in
turn alters the hallucinations themselves.
Such research creates pathways for social or community-based treatment,
such as reality monitoring, for individuals with schizophrenia and
other psychotic disorders, providing alternatives to, or supplementing
traditional pharmacologic management.
</p><p>Cross-cultural studies explore the way in which psychosis varies
in different cultures, countries and religions. The cultural differences
are based on the individual or shared illness narratives surrounding
cultural meanings of illness experience. In countries such as <a href="https://en.wikipedia.org/wiki/India" title="India">India</a>, <a href="https://en.wikipedia.org/wiki/Cambodia" title="Cambodia">Cambodia</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Muslim" title="Muslim">Muslim</a>
majority countries, they each share alternative epistemologies. These
are known as knowledge systems that focus on the connections between
mind, body, culture, nature, and society. Cultural perceptions of mental disorders such as psychosis or schizophrenia are believed to be caused by <a href="https://en.wikipedia.org/wiki/Jinn" title="Jinn">jinn</a> (spirits) in Muslim majority countries. Furthermore, those in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arab" title="Arab">Arab</a>-Muslim societies perceive those who act differently than the social norm as "crazy" or as abnormal behaviour.
This differs from the lived experience of individuals in India and how
they attain their perspectives on mental health issues through a variety
of spiritual and healing traditions. In Cambodia, hallucinations are linked with spirit visitation, a term they call "cultural kindling". These examples of differences are attributed to culture and the way it shapes conceptions of mental disorders. These cultural differences can be useful in bridging the gap of cultural understanding and psychiatric signs and symptoms.
</p>
<h2><span class="mw-headline" id="Diagnosis">Diagnosis</span></h2><p>To make a diagnosis of a mental illness in someone with psychosis <a href="https://en.wikipedia.org/wiki/Diagnosis_of_exclusion" title="Diagnosis of exclusion">other potential causes must be excluded</a>.
An initial assessment includes a comprehensive history and physical
examination by a health care provider. Tests may be done to exclude
substance use, medication, toxins, surgical complications, or other
medical illnesses. A person with psychosis is referred to as psychotic.
</p><p><a href="https://en.wikipedia.org/wiki/Delirium" title="Delirium">Delirium</a>
should be ruled out, which can be distinguished by visual
hallucinations, acute onset and fluctuating level of consciousness,
indicating other underlying factors, including medical illnesses. Excluding medical illnesses associated with psychosis is performed by using blood tests to measure:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Thyroid-stimulating_hormone" title="Thyroid-stimulating hormone">Thyroid-stimulating hormone</a> to exclude <a href="https://en.wikipedia.org/wiki/Hypothyroidism" title="Hypothyroidism">hypo-</a> or <a href="https://en.wikipedia.org/wiki/Hyperthyroidism" title="Hyperthyroidism">hyperthyroidism</a>,</li><li><a href="https://en.wikipedia.org/wiki/Vitamin_B12" title="Vitamin B12">Vitamin B<sub>12</sub></a> serum and urinary <a href="https://en.wikipedia.org/wiki/Methylmalonic_acid" title="Methylmalonic acid">MMA</a> to role out <a href="https://en.wikipedia.org/wiki/Pernicious_anemia" title="Pernicious anemia">pernicious anemia</a> or <a href="https://en.wikipedia.org/wiki/Vitamin_B12_deficiency" title="Vitamin B12 deficiency">vitamin B<sub>12</sub> deficiency</a>,</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Blood_tests#Blood_chemistry_tests" title="Blood tests">Basic electrolytes</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Serum_calcium" title="Serum calcium">serum calcium</a> to rule out a metabolic disturbance,</li><li><a href="https://en.wikipedia.org/wiki/Complete_blood_count" title="Complete blood count">Full blood count</a> including <a href="https://en.wikipedia.org/wiki/Erythrocyte_sedimentation_rate" title="Erythrocyte sedimentation rate">ESR</a> to rule out a systemic infection or chronic disease, and</li><li><a href="https://en.wikipedia.org/wiki/Serology" title="Serology">Serology</a> to exclude <a href="https://en.wikipedia.org/wiki/Syphilis" title="Syphilis">syphilis</a> or <a href="https://en.wikipedia.org/wiki/HIV" title="HIV">HIV</a> infection.</li></ul>
<p>Other investigations include:
</p>
<ul><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/EEG" title="EEG">EEG</a> to exclude <a href="https://en.wikipedia.org/wiki/Epilepsy" title="Epilepsy">epilepsy</a>, and an</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/MRI" title="MRI">MRI</a> or <a href="https://en.wikipedia.org/wiki/CT_scan" title="CT scan">CT scan</a> of the head to exclude brain lesions.</li></ul>
<p>Because psychosis may be precipitated or exacerbated by common classes of medications, medication-induced psychosis should be <a href="https://en.wikipedia.org/wiki/Diagnosis_of_exclusion" title="Diagnosis of exclusion">ruled out</a>, particularly for first-episode psychosis. Both substance- and medication-induced psychosis can be <a href="https://en.wikipedia.org/wiki/Diagnosis_of_exclusion" title="Diagnosis of exclusion">excluded</a> to a high level of certainty, using toxicology screening.
</p><p>Because some <a href="https://en.wikipedia.org/wiki/Dietary_supplement" title="Dietary supplement">dietary supplements</a>
may also induce psychosis or mania, but cannot be ruled out with
laboratory tests, a psychotic individual's family, partner, or friends
should be asked whether the patient is currently taking any dietary
supplements.
</p><p>Common mistakes made when diagnosing people who are psychotic include:
</p>
<ul><li>Not properly excluding <a href="https://en.wikipedia.org/wiki/Delirium" title="Delirium">delirium</a>,</li><li>Not appreciating medical abnormalities (e.g., vital signs),</li><li>Not obtaining a medical history and family history,</li><li>Indiscriminate screening without an organizing framework,</li><li>Missing a toxic psychosis by not screening for substances <i>and</i> medications,</li><li>Not asking their family or others about dietary supplements,</li><li>Premature diagnostic closure, and</li><li>Not revisiting or questioning the initial diagnostic impression of primary psychiatric disorder.</li></ul>
<p>Only after relevant and known causes of psychosis are excluded, a mental health clinician may make a psychiatric <a href="https://en.wikipedia.org/wiki/Differential_diagnosis" title="Differential diagnosis">differential diagnosis</a>
using a person's family history, incorporating information from the
person with psychosis, and information from family, friends, or
significant others.
</p><p>Types of psychosis in psychiatric disorders may be established by formal rating scales. The <a href="https://en.wikipedia.org/wiki/Brief_Psychiatric_Rating_Scale" title="Brief Psychiatric Rating Scale">Brief Psychiatric Rating Scale</a> (BPRS) assesses the level of 18 symptom constructs of psychosis such as <a href="https://en.wikipedia.org/wiki/Hostility" title="Hostility">hostility</a>, <a href="https://en.wikipedia.org/wiki/Suspicion_(emotion)" title="Suspicion (emotion)">suspicion</a>, <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">hallucination</a>, and <a href="https://en.wikipedia.org/wiki/Grandiosity" title="Grandiosity">grandiosity</a>.
It is based on the clinician's interview with the patient and
observations of the patient's behavior over the previous 2–3 days. The
patient's family can also answer questions on the behavior report.
During the initial assessment and the follow-up, both positive and
negative symptoms of psychosis can be assessed using the 30 item
Positive and Negative Symptom Scale (<a href="https://en.wikipedia.org/wiki/Positive_and_Negative_Syndrome_Scale" title="Positive and Negative Syndrome Scale">PANSS</a>).
</p><p>The <a href="https://en.wikipedia.org/wiki/DSM-5" title="DSM-5">DSM-5</a>
characterizes disorders as psychotic or on the schizophrenia spectrum
if they involve hallucinations, delusions, disorganized thinking,
grossly disorganized motor behavior, or negative symptoms.
The DSM-5 does not include psychosis as a definition in the glossary,
although it defines "psychotic features", as well as "psychoticism" with
respect to personality disorder. The <a href="https://en.wikipedia.org/wiki/ICD-10" title="ICD-10">ICD-10</a> has no specific definition of psychosis.
</p><p><a href="https://en.wikipedia.org/wiki/Factor_analysis" title="Factor analysis">Factor analysis</a>
of symptoms generally regarded as psychosis frequently yields a five
factor solution, albeit five factors that are distinct from the five
domains defined by the DSM-5 to encompass <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Psychotic_disorder" title="Psychotic disorder">psychotic</a>
or schizophrenia spectrum disorders. The five factors are frequently
labeled as hallucinations, delusions, disorganization, excitement, and
emotional distress. The DSM-5 emphasizes a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Psychotic_spectrum" title="Psychotic spectrum">psychotic spectrum</a>, wherein the low end is characterized by schizoid personality disorder, and the high end is characterized by schizophrenia.
</p>
<h2><span class="mw-headline" id="Prevention">Prevention</span></h2><p>The evidence for the effectiveness of early interventions to <a href="https://en.wikipedia.org/wiki/Mental_disorder#Prevention" title="Mental disorder">prevent</a> psychosis appeared inconclusive. But psychosis caused by drugs can be prevented.
Whilst early intervention in those with a psychotic episode might
improve short-term outcomes, little benefit was seen from these measures
after five years. However, there is evidence that <a href="https://en.wikipedia.org/wiki/Cognitive_behavioral_therapy" title="Cognitive behavioral therapy">cognitive behavioral therapy</a> (CBT) may reduce the risk of becoming psychotic in those at high risk, and in 2014 the UK <a href="https://en.wikipedia.org/wiki/National_Institute_for_Health_and_Care_Excellence" title="National Institute for Health and Care Excellence">National Institute for Health and Care Excellence (NICE)</a> recommended preventive CBT for people at risk of psychosis.
</p>
<h2><span class="mw-headline" id="Treatment">Treatment</span></h2><p>The
treatment of psychosis depends on the specific diagnosis (such as
schizophrenia, bipolar disorder or substance intoxication). The
first-line treatment for many psychotic disorders is antipsychotic
medication,
which can reduce the positive symptoms of psychosis in about 7 to 14
days. For youth or adolescents, treatment options include medications,
psychological interventions, and social interventions.
</p>
<h3><span class="mw-headline" id="Medication_2">Medication</span></h3><p>The choice of which <a href="https://en.wikipedia.org/wiki/Antipsychotic" title="Antipsychotic">antipsychotic</a> to use is based on benefits, risks, and costs. It is debatable whether, as a class, <a href="https://en.wikipedia.org/wiki/Typical_antipsychotic" title="Typical antipsychotic">typical</a> or <a href="https://en.wikipedia.org/wiki/Atypical_antipsychotic" title="Atypical antipsychotic">atypical antipsychotics</a> are better. Tentative evidence supports that <a href="https://en.wikipedia.org/wiki/Amisulpride" title="Amisulpride">amisulpride</a>, <a href="https://en.wikipedia.org/wiki/Olanzapine" title="Olanzapine">olanzapine</a>, <a href="https://en.wikipedia.org/wiki/Risperidone" title="Risperidone">risperidone</a> and <a href="https://en.wikipedia.org/wiki/Clozapine" title="Clozapine">clozapine</a> may be more effective for positive symptoms but result in more side effects. Typical antipsychotics have equal drop-out and symptom relapse rates to atypicals when used at low to moderate dosages.
There is a good response in 40–50%, a partial response in 30–40%, and
treatment resistance (failure of symptoms to respond satisfactorily
after six weeks to two or three different antipsychotics) in 20% of
people.
Clozapine is an effective treatment for those who respond poorly to
other drugs ("treatment-resistant" or "refractory" schizophrenia), but it has the potentially serious side effect of <a href="https://en.wikipedia.org/wiki/Agranulocytosis" title="Agranulocytosis">agranulocytosis</a> (lowered <a href="https://en.wikipedia.org/wiki/White_blood_cell" title="White blood cell">white blood cell</a> count) in less than 4% of people.
</p><p>Most people on antipsychotics get side effects. People on typical antipsychotics tend to have a higher rate of <a href="https://en.wikipedia.org/wiki/Extrapyramidal_symptoms" title="Extrapyramidal symptoms">extrapyramidal side effects</a> while some atypicals are associated with considerable weight gain, diabetes and risk of <a href="https://en.wikipedia.org/wiki/Metabolic_syndrome" title="Metabolic syndrome">metabolic syndrome</a>; this is most pronounced with olanzapine, while risperidone and <a href="https://en.wikipedia.org/wiki/Quetiapine" title="Quetiapine">quetiapine</a> are also associated with weight gain. Risperidone has a similar rate of extrapyramidal symptoms to haloperidol.
</p>
<h3><span class="mw-headline" id="Psychotherapy">Psychotherapy</span></h3><p>Psychological treatments such as <a href="https://en.wikipedia.org/wiki/Acceptance_and_commitment_therapy" title="Acceptance and commitment therapy">acceptance and commitment therapy</a>
(ACT) are possibly useful in the treatment of psychosis, helping people
to focus more on what they can do in terms of valued life directions
despite challenging symptomology. <a href="https://en.wikipedia.org/wiki/Metacognitive_training" title="Metacognitive training">Metacognitive training</a> (MCT) is associated with reduced <a href="https://en.wikipedia.org/wiki/Delusion" title="Delusion">delusions</a>, <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">hallucinations</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Negative_symptoms" title="Negative symptoms">negative symptoms</a> as well as improved <a href="https://en.wikipedia.org/wiki/Self-esteem" title="Self-esteem">self-esteem</a> and functioning in individuals with schizophrenia spectrum disorders.
</p><p>There are many psychosocial interventions that seek to treat the symptoms of psychosis: <a class="new" href="https://en.wikipedia.org/w/index.php?title=Need_adapted_treatment&action=edit&redlink=1" title="Need adapted treatment (page does not exist)">need adapted treatment</a>, <a href="https://en.wikipedia.org/wiki/Open_Dialogue" title="Open Dialogue">Open Dialogue</a>, psychoanalysis/psychodynamic psychotherapy, <a class="new" href="https://en.wikipedia.org/w/index.php?title=Major_role_therapy&action=edit&redlink=1" title="Major role therapy (page does not exist)">major role therapy</a>, <a href="https://en.wikipedia.org/wiki/Soteria_(psychiatric_treatment)" title="Soteria (psychiatric treatment)">soteria</a>, psychosocial outpatient and inpatient treatment, <a href="https://en.wikipedia.org/wiki/Milieu_therapy" title="Milieu therapy">milieu therapy</a>, and cognitive behavioral therapy (<a href="https://en.wikipedia.org/wiki/Cognitive_behavioral_therapy" title="Cognitive behavioral therapy">CBT</a>).
When these are used without antipsychotic medications, they may be
somewhat effective for some people, especially for CBT, need-adapted
treatment, and soteria.
</p>
<h3><span class="mw-headline" id="Early_intervention">Early intervention</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Early_intervention_in_psychosis" title="Early intervention in psychosis">Early intervention in psychosis</a></div>
<p><a href="https://en.wikipedia.org/wiki/Early_intervention_in_psychosis" title="Early intervention in psychosis">Early intervention in psychosis</a>
is based on the observation that identifying and treating someone in
the early stages of a psychosis can improve their longer term outcome. This approach advocates the use of an intensive multi-disciplinary approach during what is known as the <a href="https://en.wikipedia.org/wiki/Critical_period" title="Critical period">critical period</a>, where intervention is the most effective, and prevents the long-term morbidity associated with chronic psychotic illness.
</p>
<h3><span class="mw-headline" id="Systematic_reform">Systematic reform</span></h3><p>Addressing
systematic reform is essential to creating effective prevention as well
as supporting treatments and recovery for those with psychosis.
</p><p>Waghorn et al.
suggest that education interventions can be a building block to support
those with psychosis to successfully participate in society. In their
study they analyse the relationship between successful education
attainment and psychosis. Findings suggest proportionately more school
aged persons with psychosis discontinued their education, compared to
those without psychosis.
</p><p>Waghorn et al.
finds that specialised supported education for those with psychotic
disorders can help lead to successful education attainment.
Additionally, future employment outcomes are relative to such education
attainment. Established approaches to supported education in the US
include three basic models, self-contained classrooms, onsite support
model and the mobile support model. Each model includes the
participation of mental health service staff or educational facility
staff in the student's education arrangements.
</p><p>Potential benefits of specialised supported education found from
this study include coordination with other service providers (e.g.
income support, housing, etc.) to prevent disrupting education,
providing specialised career counselling, development of coping skills
in the academic environment.
These examples provide beneficial ways for people with psychosis to
finish studies successfully as well as counter future experiences of
psychosis.
</p>
<h2><span class="mw-headline" id="History">History</span></h2><h3><span class="mw-headline" id="Etymology">Etymology</span></h3><p>The word <i>psychosis</i> was introduced to the psychiatric literature in 1841 by <a href="https://en.wikipedia.org/wiki/Karl_Friedrich_Canstatt" title="Karl Friedrich Canstatt">Karl Friedrich Canstatt</a> in his work <i>Handbuch der Medizinischen Klinik</i>. He used it as a shorthand for 'psychic neurosis'. At that time neurosis meant any disease of the <a href="https://en.wikipedia.org/wiki/Nervous_system" title="Nervous system">nervous system</a>, and Canstatt was thus referring to what was considered a psychological manifestation of brain disease. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Baron_Ernst_Von_Feuchtersleben" title="Baron Ernst Von Feuchtersleben">Ernst von Feuchtersleben</a> is also widely credited as introducing the term in 1845, as an alternative to <a href="https://en.wikipedia.org/wiki/Insanity" title="Insanity">insanity</a> and <a href="https://en.wikipedia.org/wiki/Mania" title="Mania">mania</a>.
</p><p>The term stems from <a href="https://en.wikipedia.org/wiki/Neo-Latin" title="Neo-Latin">Modern Latin</a> <i>psychosis</i>, "a giving soul or life to, animating, quickening" and that from <a href="https://en.wikipedia.org/wiki/Ancient_Greek" title="Ancient Greek">Ancient Greek</a> ψυχή (<span title="Ancient Greek (to 1453)-language text"><i lang="grc">psyche</i></span>), "soul" and the suffix -ωσις (-<i><span title="Ancient Greek (to 1453)-language text"><i lang="grc">osis</i></span></i>), in this case "abnormal condition".
</p><p>In its adjective form "psychotic", references to psychosis can be
found in both clinical and non-clinical discussions. However, in a <i>non</i>-clinical context, "psychotic" is a nonspecific colloquialism used to mean "insane".
</p>
<h3><span class="mw-headline" id="Classification">Classification</span></h3><p>The word was also used to distinguish a condition considered a disorder of the mind, as opposed to <i><a href="https://en.wikipedia.org/wiki/Neurosis" title="Neurosis">neurosis</a></i>, which was considered a disorder of the nervous system. The psychoses thus became the modern equivalent of the old notion of <a href="https://en.wikipedia.org/wiki/Insanity" title="Insanity">madness</a>, and hence there was much debate on whether there was only one <a href="https://en.wikipedia.org/wiki/Unitary_psychosis" title="Unitary psychosis">(unitary)</a> or many forms of the new disease. One type of broad usage would later be narrowed down by <a href="https://en.wikipedia.org/wiki/Julius_Ludwig_August_Koch" title="Julius Ludwig August Koch">Koch</a> in 1891 to the 'psychopathic inferiorities'—later renamed abnormal personalities by <a href="https://en.wikipedia.org/wiki/Kurt_Schneider" title="Kurt Schneider">Schneider</a>.
</p><p>The division of the major psychoses into manic depressive illness (now called <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a>) and dementia praecox (now called <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a>) was made by <a href="https://en.wikipedia.org/wiki/Emil_Kraepelin" title="Emil Kraepelin">Emil Kraepelin</a>, who attempted to create a synthesis of the various mental disorders identified by 19th-century <a href="https://en.wikipedia.org/wiki/Psychiatry" title="Psychiatry">psychiatrists</a>,
by grouping diseases together based on classification of common
symptoms. Kraepelin used the term 'manic depressive insanity' to
describe the whole spectrum of <a href="https://en.wikipedia.org/wiki/Mood_disorder" title="Mood disorder">mood disorders</a>, in a far wider sense than it is usually used today.
</p><p>In Kraepelin's classification this would include 'unipolar' <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Clinical_depression" title="Clinical depression">clinical depression</a>, as well as bipolar disorder and other mood disorders such as <a href="https://en.wikipedia.org/wiki/Cyclothymia" title="Cyclothymia">cyclothymia</a>.
These are characterised by problems with mood control and the psychotic
episodes appear associated with disturbances in mood, and patients
often have periods of normal functioning between psychotic episodes even
without medication. <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">Schizophrenia</a>
is characterized by psychotic episodes that appear unrelated to
disturbances in mood, and most non-medicated patients show signs of
disturbance between psychotic episodes.
</p>
<h3><span class="mw-headline" id="Treatment_2">Treatment</span></h3><p>Early
civilizations considered madness a supernaturally inflicted phenomenon.
Archaeologists have unearthed skulls with clearly visible drillings,
some datable back to 5000 BC suggesting that <a href="https://en.wikipedia.org/wiki/Trepanning" title="Trepanning">trepanning</a> was a common treatment for psychosis in ancient times. Written record of supernatural causes and resultant treatments can be traced back to the <a href="https://en.wikipedia.org/wiki/New_Testament" title="New Testament">New Testament</a>. <a href="https://en.wikipedia.org/wiki/Mark_5" title="Mark 5">Mark 5</a>:8–13 describes a man displaying what would today be described as psychotic symptoms. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Christ" title="Christ">Christ</a> cured this "<a href="https://en.wikipedia.org/wiki/Demon" title="Demon">demonic</a>
madness" by casting out the demons and hurling them into a herd of
swine. Exorcism is still utilized in some religious circles as a
treatment for psychosis presumed to be demonic possession.
A research study of out-patients in psychiatric clinics found that 30
percent of religious patients attributed the cause of their psychotic
symptoms to evil spirits. Many of these patients underwent exorcistic
healing rituals that, though largely regarded as positive experiences by
the patients, had no effect on symptomology. Results did, however, show
a significant worsening of psychotic symptoms associated with exclusion
of medical treatment for coercive forms of exorcism.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Hippocrates.jpg"><img class="mw-file-element" data-file-height="710" data-file-width="483" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Hippocrates.jpg/220px-Hippocrates.jpg" width="272" /></a><figcaption>Bust of Hippocrates</figcaption></figure>
<p>The medical teachings of the fourth-century philosopher and physician <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hippocrates_of_Cos" title="Hippocrates of Cos">Hippocrates of Cos</a> proposed a natural, rather than supernatural, cause of human illness. In Hippocrates' work, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hippocratic_corpus" title="Hippocratic corpus">Hippocratic corpus</a>,
a holistic explanation for health and disease was developed to include
madness and other "diseases of the mind". Hippocrates writes:
</p>
<blockquote class="templatequote"><p>Men ought to know that from the
brain, and from the brain only, arise our pleasures, joys, laughter, and
jests, as well as our sorrows, pains, griefs and tears. Through it, in
particular, we think, see, hear, and distinguish the ugly from the
beautiful, the bad from the good, the pleasant from the unpleasant....
It is the same thing which makes us mad or delirious, inspires us with
dread and fear, whether by night or by day, brings sleeplessness,
inopportune mistakes, aimless anxieties, absentmindedness, and acts that
are contrary to habit.</p></blockquote>
<p>Hippocrates espoused a theory of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Humoralism" title="Humoralism">humoralism</a> wherein disease is resultant of a shifting balance in bodily fluids including <a href="https://en.wikipedia.org/wiki/Blood" title="Blood">blood</a>, <a href="https://en.wikipedia.org/wiki/Phlegm" title="Phlegm">phlegm</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Black_bile" title="Black bile">black bile</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Yellow_bile" title="Yellow bile">yellow bile</a>. According to humoralism, each fluid or "<a href="https://en.wikipedia.org/wiki/Humour" title="Humour">humour</a>"
has temperamental or behavioral correlates. In the case of psychosis,
symptoms are thought to be caused by an excess of both blood and yellow
bile. Thus, the proposed surgical intervention for psychotic or manic
behavior was <a href="https://en.wikipedia.org/wiki/Bloodletting" title="Bloodletting">bloodletting</a>.
</p><p>18th-century physician, educator, and widely considered "founder of American psychiatry", <a href="https://en.wikipedia.org/wiki/Benjamin_Rush" title="Benjamin Rush">Benjamin Rush</a>,
also prescribed bloodletting as a first-line treatment for psychosis.
Although not a proponent of humoralism, Rush believed that active
purging and bloodletting were efficacious corrections for disruptions in
the circulatory system, a complication he believed was the primary
cause of "insanity".
Although Rush's treatment modalities are now considered antiquated and
brutish, his contributions to psychiatry, namely the biological
underpinnings of psychiatric phenomenon including psychosis, have been
invaluable to the field. In honor of such contributions, Benjamin Rush's
image is in the official seal of the <a href="https://en.wikipedia.org/wiki/American_Psychiatric_Association" title="American Psychiatric Association">American Psychiatric Association</a>.
</p><p>Early 20th-century treatments for severe and persisting psychosis
were characterized by an emphasis on shocking the nervous system. Such
therapies include <a href="https://en.wikipedia.org/wiki/Insulin_shock_therapy" title="Insulin shock therapy">insulin shock therapy</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cardiazol" title="Cardiazol">cardiazol</a> shock therapy, and <a href="https://en.wikipedia.org/wiki/Electroconvulsive_therapy" title="Electroconvulsive therapy">electroconvulsive therapy</a>. Despite considerable risk, shock therapy was considered highly efficacious in the treatment of psychosis including <a href="https://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia">schizophrenia</a>. The acceptance of high-risk treatments led to more invasive medical interventions including <a href="https://en.wikipedia.org/wiki/Psychosurgery" title="Psychosurgery">psychosurgery</a>.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Gottlieb_Burckhardt_(1836-1907).jpg"><img class="mw-file-element" data-file-height="987" data-file-width="704" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Gottlieb_Burckhardt_%281836-1907%29.jpg/220px-Gottlieb_Burckhardt_%281836-1907%29.jpg" width="286" /></a><figcaption>Gottlieb Burckhardt (1836–1907)</figcaption></figure>
<p>In 1888, Swiss psychiatrist <a href="https://en.wikipedia.org/wiki/Gottlieb_Burckhardt" title="Gottlieb Burckhardt">Gottlieb Burckhardt</a> performed the first medically sanctioned psychosurgery in which the <a href="https://en.wikipedia.org/wiki/Cerebral_cortex" title="Cerebral cortex">cerebral cortex</a>
was excised. Although some patients showed improvement of symptoms and
became more subdued, one patient died and several developed <a href="https://en.wikipedia.org/wiki/Aphasia" title="Aphasia">aphasia</a>
or seizure disorders. Burckhardt would go on to publish his clinical
outcomes in a scholarly paper. This procedure was met with criticism
from the medical community and his academic and surgical endeavors were
largely ignored. In the late 1930s, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Egas_Moniz" title="Egas Moniz">Egas Moniz</a> conceived the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Leucotomy" title="Leucotomy">leucotomy</a> (AKA <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Prefrontal_lobotomy" title="Prefrontal lobotomy">prefrontal lobotomy</a>) in which the fibers connecting the <a href="https://en.wikipedia.org/wiki/Frontal_lobe" title="Frontal lobe">frontal lobes</a>
to the rest of the brain were severed. Moniz's primary inspiration
stemmed from a demonstration by neuroscientists John Fulton and
Carlyle's 1935 experiment in which two chimpanzees were given
leucotomies and pre- and post-surgical behavior was compared. Prior to
the leucotomy, the chimps engaged in typical behavior including throwing
feces and fighting. After the procedure, both chimps were pacified and
less violent. During the Q&A, Moniz asked if such a procedure could
be extended to human subjects, a question that Fulton admitted was quite
startling.
Moniz would go on to extend the controversial practice to humans with
various psychotic disorders, an endeavor for which he received a <a href="https://en.wikipedia.org/wiki/Nobel_Prize" title="Nobel Prize">Nobel Prize</a> in 1949. Between the late 1930s and early 1970s, the leucotomy was a widely accepted practice, often performed in non-<a href="https://en.wikipedia.org/wiki/Sterilization_(microbiology)" title="Sterilization (microbiology)">sterile</a> environments such as small <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Outpatient" title="Outpatient">outpatient</a> clinics and patient homes. Psychosurgery remained standard practice until the discovery of antipsychotic pharmacology in the 1950s.
</p><p>The first clinical trial of <a href="https://en.wikipedia.org/wiki/Antipsychotic" title="Antipsychotic">antipsychotics</a> (also commonly known as neuroleptics) for the treatment of psychosis took place in 1952. <a href="https://en.wikipedia.org/wiki/Chlorpromazine" title="Chlorpromazine">Chlorpromazine</a>
(brand name: Thorazine) passed clinical trials and became the first
antipsychotic medication approved for the treatment of both acute and
chronic psychosis. Although the mechanism of action was not discovered
until 1963, the administration of chlorpromazine marked the advent of
the <a href="https://en.wikipedia.org/wiki/Dopamine_antagonist" title="Dopamine antagonist">dopamine antagonist</a>, or first generation antipsychotic. While clinical trials showed a high response rate for both acute psychosis and disorders with psychotic features, the <a href="https://en.wikipedia.org/wiki/Side_effect" title="Side effect">side effects</a> were particularly harsh, which included high rates of often irreversible Parkinsonian symptoms such as <a href="https://en.wikipedia.org/wiki/Tardive_dyskinesia" title="Tardive dyskinesia">tardive dyskinesia</a>. With the advent of <a href="https://en.wikipedia.org/wiki/Atypical_antipsychotic" title="Atypical antipsychotic">atypical antipsychotics</a>
(also known as second generation antipsychotics) came a dopamine
antagonist with a comparable response rate but a far different, though
still extensive, side-effect profile that included a lower risk of
Parkinsonian symptoms but a higher risk of cardiovascular disease. Atypical antipsychotics remain the first-line treatment for psychosis associated with various psychiatric and <a href="https://en.wikipedia.org/wiki/Neurological_disorder" title="Neurological disorder">neurological disorders</a> including schizophrenia, <a href="https://en.wikipedia.org/wiki/Bipolar_disorder" title="Bipolar disorder">bipolar disorder</a>, <a href="https://en.wikipedia.org/wiki/Major_depressive_disorder" title="Major depressive disorder">major depressive disorder</a>, <a href="https://en.wikipedia.org/wiki/Anxiety_disorder" title="Anxiety disorder">anxiety disorders</a>, <a href="https://en.wikipedia.org/wiki/Dementia" title="Dementia">dementia</a>, and some <a href="https://en.wikipedia.org/wiki/Autism_spectrum" title="Autism spectrum">autism spectrum</a> disorders.
</p><p>Dopamine is now one of the primary neurotransmitters implicated
in psychotic symptomology. Blocking dopamine receptors (namely, the
dopamine D2 receptors) and decreasing dopaminergic activity continues to
be an effective but highly unrefined effect of antipsychotics, which
are commonly used to treat psychosis. Recent pharmacological research
suggests that the decrease in dopaminergic activity does not eradicate
psychotic <a href="https://en.wikipedia.org/wiki/Delusion" title="Delusion">delusions</a> or <a href="https://en.wikipedia.org/wiki/Hallucination" title="Hallucination">hallucinations</a>,
but rather attenuates the reward mechanisms involved in the development
of delusional thinking; that is, connecting or finding meaningful
relationships between unrelated stimuli or ideas. The author of this research paper acknowledges the importance of future investigation:
</p>
<blockquote class="templatequote"><p>The model presented here is based
on incomplete knowledge related to dopamine, schizophrenia, and
antipsychotics—and as such will need to evolve as more is known about
these.</p><div class="templatequotecite">— <cite>Shitij Kapur, From dopamine to salience to psychosis—linking biology, pharmacology and phenomenology of psychosis</cite></div></blockquote>
<p><a href="https://en.wikipedia.org/wiki/Sigmund_Freud" title="Sigmund Freud">Freud</a>'s
former student Wilhelm Reich explored independent insights into the
physical effects of neurotic and traumatic upbringing, and published his
holistic psychoanalytic treatment with a schizophrenic. With his
incorporation of breathwork and insight with the patient, a young woman,
she achieved sufficient self-management skills to end the therapy.
</p><p><a href="https://en.wikipedia.org/wiki/Jacques_Lacan" title="Jacques Lacan">Lacan</a> extended Freud's ideas to create a psychoanalytic model of psychosis based upon the concept of "<a href="https://en.wikipedia.org/wiki/Foreclosure_(psychoanalysis)" title="Foreclosure (psychoanalysis)">foreclosure</a>", the rejection of the symbolic concept of the father.
</p><p>Psychiatrist <a href="https://en.wikipedia.org/wiki/David_Healy_(psychiatrist)" title="David Healy (psychiatrist)">David Healy</a>
has criticised pharmaceutical companies for promoting simplified
biological theories of mental illness that seem to imply the primacy of
pharmaceutical treatments while ignoring social and developmental
factors that are known important influences in the etiology of
psychosis.
</p>
<h2><span class="mw-headline" id="Society_and_culture">Society and culture</span></h2><h3><span class="mw-headline" id="Disability">Disability</span></h3><p>The classification of psychosis as a <a href="https://en.wikipedia.org/wiki/Social_model_of_disability" title="Social model of disability">social disability</a> is a common occurrence.
</p><p>Psychosis is considered to be among the top 10 causes of social disability among adult men and women in developed countries.
And the traditional, negative narrative around disability has been
shown to strongly and adversely influence the pathways through
employment and education for people experiencing psychosis.
</p><p>Social disability by way of social disconnection is a significant
public health concern and is associated with a broad range of negative
outcomes, including premature mortality. Social disconnection refers to
the ongoing absence of family or social relationships with marginal
participation in social activities.
</p><p>Research on psychosis found that reduced participation in social
networks, not only negatively effects the individual on a physical and
mental level, it has been shown that failure to be included in social
networks influences the individual's ability to participate in the wider
community through employment and education opportunities.
</p><p>Equal opportunity to participate in meaningful relationships with
friends, family and partners, as well as engaging in social constructs
such as employment, can provide significant physical and mental value to
people's lives.
And how breaking the disability mindset around people experiencing
psychosis is imperative for their overall, long-term health and
well-being as well as the contributions they are able to make to their
immediate social connections and the wider community.
</p>
<h2><span class="mw-headline" id="Research">Research</span></h2><p>Further
research in the form of randomized controlled trials is needed to
determine the effectiveness of treatment approaches for helping <i>adolescents</i> with psychosis.
Through 10 randomized clinical trials, studies showed that Early
Intervention Services (EIS) for patients with early-phase schizophrenia
spectrum disorders have generated promising outcomes. EIS are specifically intended to fulfill the needs of patients with early-phase psychosis.
In addition, one meta-analysis that consisted of four randomized
clinical trials has examined and discovered the efficacy of EIS to
Therapy as Usual (TAU) for early-phase psychosis, revealing that EIS
techniques are superior to TAU.
</p><p>A study suggests that combining cognitive behavioral therapy
(CBT) with SlowMo, an app that helps notice their "unhelpful
quick-thinking", might be more effective for treating paranoia in people
with psychosis than CBT alone.</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-32969528542648512732024-03-17T20:53:00.002-04:002024-03-17T20:53:08.673-04:00Id, ego and superego<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
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<div class="hatnote navigation-not-searchable" role="note"><a href="https://en.wikipedia.org/wiki/Id,_ego_and_superego">https://en.wikipedia.org/wiki/Id,_ego_and_superego</a></div><div class="hatnote navigation-not-searchable" role="note"> </div><div class="hatnote navigation-not-searchable" role="note">In <a href="https://en.wikipedia.org/wiki/Psychoanalytic_theory" title="Psychoanalytic theory">psychoanalytic theory</a>, the <b>id, ego and superego</b> are three distinct, interacting agents in the <a href="https://en.wikipedia.org/wiki/Psychic_apparatus" title="Psychic apparatus">psychic apparatus</a>, defined in <a href="https://en.wikipedia.org/wiki/Sigmund_Freud" title="Sigmund Freud">Sigmund Freud</a>'s structural model of the <a href="https://en.wikipedia.org/wiki/Psyche_(psychology)" title="Psyche (psychology)">psyche</a>.
The three agents are theoretical constructs that Freud employed to
describe the basic structure of mental life as it was encountered in
psychoanalytic practice. Freud himself used the <a href="https://en.wikipedia.org/wiki/German_language" title="German language">German</a> terms <i>das Es</i>, <i>Ich</i>, and <i>Über-Ich</i>, which literally translate as "the it", "I", and "over-I". The <a href="https://en.wikipedia.org/wiki/Latin" title="Latin">Latin</a> terms id, ego and superego were chosen by his original translators and have remained in use.
</div></div></div></div><p>In the <a href="https://en.wikipedia.org/wiki/Ego_psychology" title="Ego psychology">ego psychology</a> model of the psyche, the <b>id</b> is the set of uncoordinated <a href="https://en.wikipedia.org/wiki/Instinct" title="Instinct">instinctual</a> desires; the <b>superego</b> plays the critical and moralizing role; and the <b>ego</b> is the organized, realistic agent that mediates between the instinctual <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Desires" title="Desires">desires</a> of the id and the critical superego;
Freud compared the ego (in its relation to the id) to a man on
horseback: the rider must harness and direct the superior energy of his
mount, and at times allow for a practicable satisfaction of its urges.
The ego is thus "in the habit of transforming the id's will into action,
as if it were its own."
</p><p>Freud introduced the structural model (id, ego, superego) in the essay <i><a href="https://en.wikipedia.org/wiki/Beyond_the_Pleasure_Principle" title="Beyond the Pleasure Principle">Beyond the Pleasure Principle</a></i> (1920) in response to the unstructured ambiguity and conflicting uses of the term "the <a href="https://en.wikipedia.org/wiki/Unconscious_mind" title="Unconscious mind">unconscious mind</a>". He elaborated, refined, and formalized that model in the essay <i><a href="https://en.wikipedia.org/wiki/The_Ego_and_the_Id" title="The Ego and the Id">The Ego and the Id</a></i> (1923). <span class="mw-headline" id="Translation_of_the_terms"> </span></p><p><span class="mw-headline" id="Translation_of_the_terms">Translation of the terms</span></p><p>The terms "id", "ego", and "superego" are not Freud's own; they are Latinizations by his translator <a href="https://en.wikipedia.org/wiki/James_Strachey" title="James Strachey">James Strachey</a>. Freud himself wrote of "<i><a class="extiw" href="https://en.wiktionary.org/wiki/das#German" title="wikt:das">das</a> <a class="extiw" href="https://en.wiktionary.org/wiki/Es#German" title="wikt:Es">Es</a></i>", "<i>das <a class="extiw" href="https://en.wiktionary.org/wiki/Ich" title="wikt:Ich">Ich</a></i>", and "<i>das <a class="extiw" href="https://en.wiktionary.org/wiki/%C3%BCber-" title="wikt:über-">Über-</a>Ich</i>"—respectively,
"the It", "the I", and "the Over-I". Thus, to the German reader,
Freud's original terms are to some degree self-explanatory. The term "<i>das Es</i>" was originally used by <a href="https://en.wikipedia.org/wiki/Georg_Groddeck" title="Georg Groddeck">Georg Groddeck</a>,
a physician whose unconventional ideas were of interest to Freud
(Groddeck's translators render the term in English as "the It"). The word <i><a class="extiw" href="https://en.wiktionary.org/wiki/ego" title="wikt:ego">ego</a></i> is taken directly from <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Latin_language" title="Latin language">Latin</a>, where it is the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Nominative" title="Nominative">nominative</a> of the first person singular <a href="https://en.wikipedia.org/wiki/Personal_pronoun" title="Personal pronoun">personal pronoun</a> and is translated as "I myself" to express emphasis.
Figures like <a href="https://en.wikipedia.org/wiki/Bruno_Bettelheim" title="Bruno Bettelheim">Bruno Bettelheim</a> have criticized the way "the English translations impeded students' efforts to gain a true understanding of Freud" by substituting the formalised language of the <a href="https://en.wikipedia.org/wiki/Basil_Bernstein" title="Basil Bernstein">elaborated code</a> for the quotidian immediacy of Freud's own language.
</p>
<h2><span class="mw-headline" id="Psychic_apparatus">Psychic apparatus</span></h2><h3><span class="mw-headline" id="Id">Id</span></h3><p>Freud conceived the id as the unconscious source of bodily needs and wants, emotional impulses and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Desires" title="Desires">desires</a>, especially aggression and the sexual drive. The id acts according to the <a href="https://en.wikipedia.org/wiki/Pleasure_principle_(psychology)" title="Pleasure principle (psychology)">pleasure principle</a>—the psychic force oriented to immediate gratification of impulse and desire.
</p><p>Freud described the id as "the dark, inaccessible part of our
personality". Understanding of the id is limited to analysis of dreams
and neurotic symptoms, and it can only be described in terms of its
contrast with the ego. It has no organisation and no collective will: it
is concerned only with satisfaction of drives in accordance with the
pleasure principle.
It is oblivious to reason and the presumptions of ordinary conscious
life: "contrary impulses exist side by side, without cancelling each
other. . . There is nothing in the id that could be compared with
negation. . . nothing in the id which corresponds to the idea of time." The id "knows no judgements of value: no good and evil, no morality. ...Instinctual <a href="https://en.wikipedia.org/wiki/Cathexis" title="Cathexis">cathexes</a> seeking discharge—that, in our view, is all there is in the id."
</p><p>Developmentally, the id precedes the ego. The id consists of the
basic instinctual drives that are present at birth, inherent in the
somatic organization, and governed only by the pleasure principle.
The psychic apparatus begins as an undifferentiated id, part of which
then develops into a structured "ego", a concept of self that takes the
principle of reality into account.
</p><p>Freud describes the id as "the great reservoir of <a href="https://en.wikipedia.org/wiki/Libido" title="Libido">libido</a>",
the energy of desire, usually conceived as sexual in nature, the life
instincts that are constantly seeking a renewal of life. He later also
postulated a <a href="https://en.wikipedia.org/wiki/Death_drive" title="Death drive">death drive</a>, which seeks "to lead organic life back into the inanimate state." For Freud, "the death instinct would thus seem to express itself—though probably only in part—as an <i>instinct of destruction</i> directed against the external world and other organisms" through aggression. Since the id includes all instinctual impulses, the destructive instinct, as well as <a href="https://en.wikipedia.org/wiki/Eros_(concept)" title="Eros (concept)">eros</a> or the life instincts, is considered to be part of the id.
</p>
<h3><span class="mw-headline" id="Ego">Ego</span></h3><p>The ego acts according to the <a href="https://en.wikipedia.org/wiki/Reality_principle" title="Reality principle">reality principle</a>.
Since the id's drives are frequently incompatible with social reality,
the ego attempts to direct its energy and satisfy its demands in
accordance with the imperatives of that reality.
According to Freud the ego, in its role as mediator between the id and
reality, is often "obliged to cloak the (unconscious) commands of the id
with its own <a href="https://en.wikipedia.org/wiki/Preconscious" title="Preconscious">preconscious</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rationalization_(making_excuses)" title="Rationalization (making excuses)">rationalizations</a>,
to conceal the id's conflicts with reality, to profess...to be taking
notice of reality even when the id has remained rigid and unyielding."
</p><p>Originally, Freud used the word ego to mean the sense of self,
but later expanded it to include psychic functions such as judgment,
tolerance, reality testing, control, planning, defense, synthesis of
information, intellectual functioning, and memory. The ego is the
organizing principle upon which thoughts and interpretations of the
world are based.
</p><p>According to Freud, "the ego is that part of the id which has
been modified by the direct influence of the external world. ...The ego
represents what may be called reason and common sense, in contrast to
the id, which contains the passions... it is like a tug of war... with
the difference that in the tug of war the teams fight against one
another in equality, while the ego is against the much stronger 'id'." In fact, the ego is required to serve "three severe masters...the external world, the superego and the id."
It seeks to find a balance between the primitive drives of the id, the
limitations imposed by reality, and the strictures of the superego. It
is concerned with self-preservation: it strives to keep the id's desires
within limits, adapted to reality and submissive to the superego.
</p><p>Thus "driven by the id, confined by the superego, repulsed by
reality" the ego struggles to bring about harmony among the competing
forces. Consequently, it can easily be subject to "realistic anxiety
regarding the external world, moral anxiety regarding the superego, and
neurotic anxiety regarding the strength of the passions in the id."
The ego may wish to serve the id, trying to gloss over the finer
details of reality to minimize conflicts, while pretending to have a
regard for reality. But the superego is constantly watching every one of
the ego's moves and punishes it with feelings of <a href="https://en.wikipedia.org/wiki/Guilt_(emotion)" title="Guilt (emotion)">guilt</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Anxiety_(mood)" title="Anxiety (mood)">anxiety</a>, and inferiority.
</p><p>To overcome this the ego employs <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Defense_mechanism" title="Defense mechanism">defense mechanisms</a>.
Defense mechanisms reduce the tension and anxiety by disguising or
transforming the impulses that are perceived as threatening. <a href="https://en.wikipedia.org/wiki/Denial" title="Denial">Denial</a>, <a href="https://en.wikipedia.org/wiki/Displacement_(psychology)" title="Displacement (psychology)">displacement</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Intellectualisation" title="Intellectualisation">intellectualization</a>, <a href="https://en.wikipedia.org/wiki/Fantasy_(psychology)" title="Fantasy (psychology)">fantasy</a>, <a href="https://en.wikipedia.org/wiki/Compensation_(psychology)" title="Compensation (psychology)">compensation</a>, <a href="https://en.wikipedia.org/wiki/Psychological_projection" title="Psychological projection">projection</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rationalization_(making_excuses)" title="Rationalization (making excuses)">rationalization</a>, <a href="https://en.wikipedia.org/wiki/Reaction_formation" title="Reaction formation">reaction formation</a>, <a href="https://en.wikipedia.org/wiki/Regression_(psychology)" title="Regression (psychology)">regression</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Psychological_repression" title="Psychological repression">repression</a>, and <a href="https://en.wikipedia.org/wiki/Sublimation_(psychology)" title="Sublimation (psychology)">sublimation</a> were the defense mechanisms Freud identified. His daughter <a href="https://en.wikipedia.org/wiki/Anna_Freud" title="Anna Freud">Anna Freud</a> identified the concepts of <a href="https://en.wikipedia.org/wiki/Undoing_(psychology)" title="Undoing (psychology)">undoing</a>, <a href="https://en.wikipedia.org/wiki/Thought_suppression" title="Thought suppression">suppression</a>, <a href="https://en.wikipedia.org/wiki/Dissociation_(psychology)" title="Dissociation (psychology)">dissociation</a>, <a href="https://en.wikipedia.org/wiki/Idealization_and_devaluation" title="Idealization and devaluation">idealization</a>, <a href="https://en.wikipedia.org/wiki/Identification_(psychology)" title="Identification (psychology)">identification</a>, <a href="https://en.wikipedia.org/wiki/Introjection" title="Introjection">introjection</a>, inversion, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Somatisation" title="Somatisation">somatization</a>, <a href="https://en.wikipedia.org/wiki/Splitting_(psychology)" title="Splitting (psychology)">splitting</a>, and substitution.
</p>
<figure class="mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Structural-Model1.png"><img class="mw-file-element" data-file-height="250" data-file-width="278" height="360" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Structural-Model1.png/200px-Structural-Model1.png" width="400" /></a><figcaption>"The
ego is not sharply separated from the id; its lower portion merges into
it.... But the repressed merges into the id as well, and is merely a
part of it. The repressed is only cut off sharply from the ego by the
resistances of repression; it can communicate with the ego through the
id." (<a href="https://en.wikipedia.org/wiki/Sigmund_Freud" title="Sigmund Freud">Sigmund Freud</a>, 1923)</figcaption></figure><p>In
a diagram of the Structural and Topographical Models of Mind, the ego
is depicted as being half in the conscious, a quarter in the <a href="https://en.wikipedia.org/wiki/Preconscious" title="Preconscious">preconscious</a>, and the other quarter in the <a href="https://en.wikipedia.org/wiki/Unconscious_mind" title="Unconscious mind">unconscious</a>.
</p><h3><span class="mw-headline" id="Superego">Superego</span></h3><p>The
superego reflects the internalization of cultural rules, mainly as
absorbed from parents, but also other authority figures, and the general
cultural ethos. Freud developed his concept of the superego from an earlier combination of the <a href="https://en.wikipedia.org/wiki/Ego_ideal" title="Ego ideal">ego ideal</a>
and the "special psychical agency which performs the task of seeing
that narcissistic satisfaction from the ego ideal is ensured...what we
call our 'conscience'."
For him the superego can be described as "a successful instance of
identification with the parental agency", and as development proceeds it
also absorbs the influence of those who have "stepped into the place of
parents — educators, teachers, people chosen as ideal models".
</p>
<blockquote class="templatequote"><p>Thus a child's super-ego is in fact
constructed on the model not of its parents but of its parents'
super-ego; the contents which fill it are the same and it becomes the
vehicle of tradition and of all the time-resisting judgments of value
which have propagated themselves in this manner from generation to
generation.</p></blockquote>
<p>The superego aims for perfection.
It is the part of the personality structure, mainly but not entirely
unconscious, that includes the individual's ego ideals, spiritual goals,
and the psychic agency, commonly called "<a href="https://en.wikipedia.org/wiki/Conscience" title="Conscience">conscience</a>",
that criticizes and prohibits the expression of drives, fantasies,
feelings, and actions. Thus the superego works in contradiction to the
id. It is an internalized mechanism that operates to confine the ego to
socially acceptable behaviour, whereas the id merely seeks instant
self-gratification.
</p><p>The superego and the ego are the product of two key factors: the state of helplessness of the child and the <a href="https://en.wikipedia.org/wiki/Oedipus_complex" title="Oedipus complex">Oedipus complex</a>.
In the case of the little boy, it forms during the dissolution of the
Oedipus complex, through a process of identification with the father
figure, following the failure to retain possession of the mother as a
love-object out of <a href="https://en.wikipedia.org/wiki/Castration_anxiety" title="Castration anxiety">fear of castration</a>. Freud described the superego and its relationship to the father figure and Oedipus complex thus:
</p>
<blockquote class="templatequote"><p>The super-ego retains the character
of the father, while the more powerful the Oedipus complex was and the
more rapidly it succumbed to repression (under the influence of
authority, religious teaching, schooling and reading), the stricter will
be the domination of the super-ego over the ego later on—in the form of
conscience or perhaps of an unconscious sense of guilt.</p></blockquote>
<p>In <i><a href="https://en.wikipedia.org/wiki/The_Ego_and_the_Id" title="The Ego and the Id">The Ego and the Id</a></i>, Freud presents "the general character of harshness and cruelty exhibited by the [ego] ideal — its dictatorial <i>Thou shalt</i>". The earlier in the child's development, the greater the estimate of parental power.
</p>
<blockquote class="templatequote"><p>. . . nor must it be forgotten that
a child has a different estimate of his parents at different periods of
his life. At the time at which the Oedipus complex gives place to the
super-ego they are something quite magnificent; but later, they lose
much of this. Identifications then come about with these later parents
as well, and indeed they regularly make important contributions to the
formation of character; but in that case they only affect the ego, they
no longer influence the super-ego, which has been determined by the
earliest parental images.</p><div class="templatequotecite">— <cite><i>New Introductory Lectures on Psychoanalysis</i>, p. 64.</cite></div></blockquote>
<p>Thus when the child is in rivalry with the parental imago it feels the dictatorial <i>Thou shalt</i>—the
manifest power that the imago represents—on four levels: (i) the
auto-erotic, (ii) the narcissistic, (iii) the anal, and (iv) the
phallic.
Those different levels of mental development, and their relations to
parental imagos, correspond to specific id forms of aggression and
affection.
</p><p>The concept of superego and the Oedipus complex is subject to
criticism for its perceived sexism. Women, who are considered to be
already castrated, do not identify with the father, and therefore, for
Freud, "their super-ego is never so inexorable, so impersonal, so
independent of its emotional origins as we require it to be in
men...they are often more influenced in their judgements by feelings of
affection or hostility."
However, Freud went on to modify his position to the effect "that the
majority of men are also far behind the masculine ideal and that all
human individuals, as a result of their human identity, combine in
themselves both masculine and feminine characteristics, otherwise known
as human characteristics."
</p>
<h2><span class="mw-headline" id="Advantages_of_the_structural_model">Advantages of the structural model</span></h2><figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Structural-Iceberg.svg"><img class="mw-file-element" data-file-height="675" data-file-width="560" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Structural-Iceberg.svg/280px-Structural-Iceberg.svg.png" width="331" /></a><figcaption>The <a href="https://en.wikipedia.org/wiki/Iceberg" title="Iceberg">iceberg</a> metaphor is often used to explain the psyche's parts in relation to one another.</figcaption></figure>
<p>In his earlier "topographic model", Freud divided the psyche into
three "regions" or "systems": "the Conscious", that which is present to
awareness at the surface level of the psyche in any given moment,
including information and stimuli from both internal and external
sources; "the <a href="https://en.wikipedia.org/wiki/Preconscious" title="Preconscious">Preconscious</a>",
consisting of material that is merely latent, not present to
consciousness but capable of becoming so; and "the Unconscious",
consisting of ideas and impulses that are made completely inaccessible
to consciousness by the act of <a href="https://en.wikipedia.org/wiki/Repression_(psychoanalysis)" title="Repression (psychoanalysis)">repression</a>.
By introducing the structural model, Freud was seeking to reduce his
reliance on the term "unconscious" in its systematic and topographic
sense—as the mental region that is foreign to the ego—by replacing it
with the concept of the 'id'."
The partition of the psyche outlined in the structural model is thus
one that cuts across the topographical model's partition of "conscious
vs. unconscious".
</p><p>Freud favoured the structural model because of the increased
degree of precision and diversification that it allowed. Although the id
is unconscious by definition, the ego and the superego are both partly
conscious and partly unconscious. With the new model, Freud felt he had
achieved a more effective classification system for mental disorders
than had been available previously:
</p>
<blockquote class="templatequote"><p><a href="https://en.wikipedia.org/wiki/Transference_neurosis" title="Transference neurosis">Transference neuroses</a> correspond to a conflict between the ego and the id; <a href="https://en.wikipedia.org/wiki/Narcissistic_neurosis" title="Narcissistic neurosis">narcissistic neuroses</a>, to a conflict between the ego and the superego; and <a href="https://en.wikipedia.org/wiki/Psychosis" title="Psychosis">psychoses</a>, to one between the ego and the external world.</p></blockquote>
<p>The three newly presented entities, however, remained closely
connected to their previous conceptions, including those that went under
different names – the systematic unconscious for the id, and the
conscience/ego ideal for the superego.
Freud never abandoned the topographical division of conscious,
preconscious, and unconscious, though he noted that "the three qualities
of consciousness and the three provinces of the mental apparatus do not
fall together into three peaceful couples...we had no right to expect
any such smooth arrangement."
</p><p>The iceberg metaphor is a commonly used visual metaphor depicting
the relationship between the ego, id and superego agencies (structural
model) and the conscious and unconscious psychic systems (topographic
model). In the iceberg metaphor the entire id and part of both the
superego and the ego are submerged in the underwater portion
representing the unconscious region of the psyche. The remaining
portions of the ego and superego are displayed above water in the
conscious region.<sup class="reference" id="cite_ref-Carlson_9-1"><a href="https://en.wikipedia.org/wiki/Id,_ego_and_superego#cite_note-Carlson-9"></a></sup></p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-43175471045768497492024-03-17T20:35:00.000-04:002024-03-17T20:35:47.047-04:00Spontaneous generation<div aria-labelledby="firstHeading" class="vector-body ve-init-mw-desktopArticleTarget-targetContainer" data-mw-ve-target-container="" id="bodyContent"><div class="vector-body-before-content"><div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Spontaneous_generation">https://en.wikipedia.org/wiki/Spontaneous_generation</a> </div><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Spontaneous_Generation_of_Seashells.svg"><img class="mw-file-element" data-file-height="720" data-file-width="1280" height="225" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/78/Spontaneous_Generation_of_Seashells.svg/300px-Spontaneous_Generation_of_Seashells.svg.png" width="400" /></a><figcaption>Spontaneous generation of seashells, according to <a href="https://en.wikipedia.org/wiki/Aristotle" title="Aristotle">Aristotle</a>, varied with the nature of the seabed. Slime gave rise to <a href="https://en.wikipedia.org/wiki/Oyster" title="Oyster">oysters</a>; sand, to <a href="https://en.wikipedia.org/wiki/Scallop" title="Scallop">scallops</a>; and the hollows of rocks, to <a href="https://en.wikipedia.org/wiki/Limpet" title="Limpet">limpets</a> and <a href="https://en.wikipedia.org/wiki/Barnacle" title="Barnacle">barnacles</a>. People kept on wondering, though, whether the eggs of these animals might not be central to the generation process.</figcaption></figure>
<p><b>Spontaneous generation</b> is a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Superseded_scientific_theories" title="Superseded scientific theories">superseded scientific theory</a> that held that living creatures could arise from nonliving <a href="https://en.wikipedia.org/wiki/Matter" title="Matter">matter</a> and that such processes were commonplace and regular. It was <a href="https://en.wikipedia.org/wiki/Hypothesis" title="Hypothesis">hypothesized</a> that certain forms, such as <a href="https://en.wikipedia.org/wiki/Flea" title="Flea">fleas</a>, could arise from inanimate matter such as dust, or that <a href="https://en.wikipedia.org/wiki/Maggot" title="Maggot">maggots</a> could arise from dead flesh. The <a href="https://en.wikipedia.org/wiki/Doctrine" title="Doctrine">doctrine</a> of spontaneous generation was coherently synthesized by the Greek philosopher and naturalist <a href="https://en.wikipedia.org/wiki/Aristotle" title="Aristotle">Aristotle</a>, who compiled and expanded the work of <a href="https://en.wikipedia.org/wiki/Pre-Socratic_philosophy" title="Pre-Socratic philosophy">earlier natural philosophers</a> and the various ancient explanations for the appearance of <a href="https://en.wikipedia.org/wiki/Organism" title="Organism">organisms</a>.
Spontaneous generation was taken as scientific fact for two millennia.
Though challenged in the 17th and 18th centuries by the experiments of
the Italian biologists <a href="https://en.wikipedia.org/wiki/Francesco_Redi" title="Francesco Redi">Francesco Redi</a> and <a href="https://en.wikipedia.org/wiki/Lazzaro_Spallanzani" title="Lazzaro Spallanzani">Lazzaro Spallanzani</a>, it was not discredited until the work of the French chemist <a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> and the Irish physicist <a href="https://en.wikipedia.org/wiki/John_Tyndall" title="John Tyndall">John Tyndall</a> in the mid-19th century.
</p><p>Rejection of spontaneous generation is no longer controversial
among biologists. By the middle of the 19th century, experiments by
Pasteur and others were considered to have disproven the traditional
theory of spontaneous generation. Attention has turned instead to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Origin_of_life" title="Origin of life">origin of life</a>, since all life seems to have <a href="https://en.wikipedia.org/wiki/Common_descent" title="Common descent">evolved from a single form</a> around four billion years ago.
</p>
<h2><span class="mw-headline" id="Description">Description</span></h2></div></div><p>"Spontaneous
generation" means both the supposed processes by which different types
of life might repeatedly emerge from specific sources other than seeds,
eggs, or parents, and the theoretical principles presented in support of
any such phenomena. Crucial to this <a href="https://en.wikipedia.org/wiki/Doctrine" title="Doctrine">doctrine</a>
are the ideas that life comes from non-life and that no causal agent,
such as a parent, is needed. Supposed examples included the seasonal
generation of mice and other animals from the mud of the <a href="https://en.wikipedia.org/wiki/Nile" title="Nile">Nile</a>, the emergence of <a href="https://en.wikipedia.org/wiki/Flea" title="Flea">fleas</a> from inanimate matter such as dust, or the appearance of <a href="https://en.wikipedia.org/wiki/Maggot" title="Maggot">maggots</a> in dead flesh. Such ideas have something in common with the modern <a href="https://en.wikipedia.org/wiki/Hypothesis" title="Hypothesis">hypothesis</a> of the <a href="https://en.wikipedia.org/wiki/Abiogenesis" title="Abiogenesis">origin of life</a>,
which asserts that life emerged some four billion years ago from
non-living materials, over a time span of millions of years, and
subsequently diversified into all the forms that now exist.
</p><p>The term <i>equivocal generation</i>, sometimes known as <i>heterogenesis</i> or <i>xenogenesis</i>, describes the supposed process by which one form of life arises from a different, unrelated form, such as <a href="https://en.wikipedia.org/wiki/Eucestoda" title="Eucestoda">tapeworms</a> from the bodies of their hosts.
</p>
<h2><span class="mw-headline" id="Antiquity">Antiquity</span></h2><h3><span class="mw-headline" id="Pre-Socratic_philosophers">Pre-Socratic philosophers</span></h3><p>Active in the 6th and 5th centuries BCE, early Greek philosophers, called <i>physiologoi</i> in antiquity (Greek: φυσιολόγοι; in English, physical or <a href="https://en.wikipedia.org/wiki/Natural_philosophy" title="Natural philosophy">natural philosophers</a>), attempted to give natural explanations of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Phenomena" title="Phenomena">phenomena</a> that had previously been ascribed to the agency of the gods. The <i>physiologoi</i> sought the material principle or <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arche" title="Arche">arche</a></i>
(Greek: ἀρχή) of things, emphasizing the rational unity of the external
world and rejecting theological or mythological explanations.
</p><p><a href="https://en.wikipedia.org/wiki/Anaximander" title="Anaximander">Anaximander</a>, who believed that all things arose from the elemental nature of the universe, the <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Apeiron_(cosmology)" title="Apeiron (cosmology)">apeiron</a></i>
(ἄπειρον) or the "unbounded" or "infinite", was likely the first
western thinker to propose that life developed spontaneously from
nonliving matter. The <a href="https://en.wikipedia.org/wiki/Substance_theory" title="Substance theory">primal chaos</a> of the <i>apeiron,</i> eternally in motion, served as a platform on which elemental opposites (e.g., <i>wet and dry</i>, <i>hot and cold</i>) generated and shaped the many and varied things in the world. According to <a href="https://en.wikipedia.org/wiki/Hippolytus_of_Rome" title="Hippolytus of Rome">Hippolytus of Rome</a>
in the third century CE, Anaximander claimed that fish or fish-like
creatures were first formed in the "wet" when acted on by the heat of
the sun and that these aquatic creatures gave rise to human beings. The Roman author <a href="https://en.wikipedia.org/wiki/Censorinus" title="Censorinus">Censorinus</a>, writing in the 3rd century, reported:
</p>
<blockquote class="templatequote"><p>Anaximander of Miletus considered
that from warmed up water and earth emerged either fish or entirely
fishlike animals. Inside these animals, men took form and embryos were
held prisoners until puberty; only then, after these animals burst open,
could men and women come out, now able to feed themselves.</p></blockquote>
<p>The Greek philosopher <a href="https://en.wikipedia.org/wiki/Anaximenes_of_Miletus" title="Anaximenes of Miletus">Anaximenes</a>,
a pupil of Anaximander, thought that air was the element that imparted
life and endowed creatures with motion and thought. He proposed that
plants and animals, including human beings, arose from a primordial
terrestrial slime, a mixture of earth and water, combined with the sun's
heat. The philosopher <a href="https://en.wikipedia.org/wiki/Anaxagoras" title="Anaxagoras">Anaxagoras</a>,
too, believed that life emerged from a terrestrial slime. However,
Anaximenes held that the seeds of plants existed in the air from the
beginning, and those of animals in the <a href="https://en.wikipedia.org/wiki/Aether_(classical_element)" title="Aether (classical element)">aether</a>. Another philosopher, <a href="https://en.wikipedia.org/wiki/Xenophanes" title="Xenophanes">Xenophanes</a>,
traced the origin of man back to the transitional period between the
fluid stage of the Earth and the formation of land, under the influence
of the Sun.
</p><p>In what has occasionally been seen as a prefiguration of a concept of <a href="https://en.wikipedia.org/wiki/Natural_selection" title="Natural selection">natural selection</a>, <a href="https://en.wikipedia.org/wiki/Empedocles" title="Empedocles">Empedocles</a>
accepted the spontaneous generation of life, but held that different
forms, made up of differing combinations of parts, spontaneously arose
as though by trial and error: successful combinations formed the
individuals present in the observer's lifetime, whereas unsuccessful
forms failed to reproduce.
</p>
<h3><span class="mw-headline" id="Aristotle">Aristotle</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Aristotle%27s_biology" title="Aristotle's biology">Aristotle's biology</a></div>
<p>In <a href="https://en.wikipedia.org/wiki/Aristotle%27s_biology" title="Aristotle's biology">his biological works</a>, the natural philosopher <a href="https://en.wikipedia.org/wiki/Aristotle" title="Aristotle">Aristotle</a> theorized extensively the reproduction of various animals, whether by <a href="https://en.wikipedia.org/wiki/Sexual_reproduction" title="Sexual reproduction">sexual</a>, <a href="https://en.wikipedia.org/wiki/Parthenogenesis" title="Parthenogenesis">parthenogenetic</a>, or spontaneous generation. In accordance with his fundamental theory of <a href="https://en.wikipedia.org/wiki/Hylomorphism" title="Hylomorphism">hylomorphism</a>,
which held that every physical entity was a compound of matter and
form, Aristotle's basic theory of sexual reproduction contended that the
<a href="https://en.wikipedia.org/wiki/Semen" title="Semen">male's seed</a> imposed form, the set of characteristics passed down to offspring on the "matter" (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Menstrual_blood" title="Menstrual blood">menstrual blood</a>) supplied by the female. Thus female matter is the <i><a href="https://en.wikipedia.org/wiki/Four_causes#Matter" title="Four causes">material cause</a></i> of generation—it supplies the matter that will constitute the offspring—while the male semen is the <i><a href="https://en.wikipedia.org/wiki/Four_causes#Agent" title="Four causes">efficient cause</a></i>, the factor that instigates and delineates the thing's existence. Yet, Aristotle proposed in the <i><a href="https://en.wikipedia.org/wiki/History_of_Animals" title="History of Animals">History of Animals</a></i>, many creatures form not through sexual processes but by spontaneous generation:
</p>
<blockquote class="templatequote"><p>Now there is one property that
animals are found to have in common with plants. For some plants are
generated from the seed of plants, whilst other plants are
self-generated through the formation of some elemental principle similar
to a seed; and of these latter plants some derive their nutriment from
the ground, whilst others grow inside other plants ... So with animals,
some spring from parent animals according to their kind, whilst others
grow spontaneously and not from kindred stock; and of these instances of
spontaneous generation some come from putrefying earth or vegetable
matter, as is the case with a number of insects, while others are
spontaneously generated in the inside of animals out of the secretions
of their several organs.</p><div class="templatequotecite">— <cite>Aristotle, <i><a href="https://en.wikipedia.org/wiki/History_of_Animals" title="History of Animals">History of Animals</a></i>, Book V, Part 1</cite></div></blockquote>
<p>According to this theory, living things may come forth from nonliving
things in a manner roughly analogous to the "enformation of the female
matter by the agency of the male seed" seen in sexual reproduction. Nonliving materials, like the seminal fluid present in sexual generation, contain <i><a href="https://en.wikipedia.org/wiki/Pneuma" title="Pneuma">pneuma</a></i> (πνεῦμα, "breath"), or "<a href="https://en.wikipedia.org/wiki/Vital_heat" title="Vital heat">vital heat</a>". According to Aristotle, <i>pneuma</i> had more "heat" than regular air did, and this heat endowed the substance with certain vital properties:
</p>
<blockquote class="templatequote"><p>The power of every soul seems to
have shared in a different and more divine body than the so called
[four] elements ... For every [animal], what makes the seed generative
inheres in the seed and is called its "heat". But this is not fire or
some such power, but instead the <i>pneuma</i> that is enclosed in the
seed and in foamy matter, this being analogous to the element of the
stars. This is why fire does not generate any animal<span class="nowrap"> </span>...
but the heat of the sun and the heat of animals does, not only the heat
that fills the seed, but also any other residue of [the animal's]
nature that may exist similarly possesses this vital principle.</p><div class="templatequotecite">— <cite>Aristotle, <i><a href="https://en.wikipedia.org/wiki/Generation_of_Animals" title="Generation of Animals">Generation of Animals</a></i>, 736b29ff</cite></div></blockquote>
<p>Aristotle drew an analogy between the "foamy matter" (τὸ ἀφρῶδες, <i>to aphrodes</i>)
found in nature and the "seed" of an animal, which he viewed as being a
kind of foam itself (composed, as it was, from a mixture of water and <i>pneuma</i>).
For Aristotle, the generative materials of male and female animals
(semen and menstrual fluid) were essentially refinements, made by male
and female bodies according to their respective proportions of heat, of
ingested food, which was, in turn, a byproduct of the elements earth and
water. Thus any creature, whether generated sexually from parents or
spontaneously through the interaction of vital heat and elemental
matter, was dependent on the proportions of <i>pneuma</i> and the various elements which Aristotle believed comprised all things. While Aristotle recognized that many living things emerged from <a href="https://en.wikipedia.org/wiki/Putrefaction" title="Putrefaction">putrefying</a>
matter, he pointed out that the putrefaction was not the source of
life, but the byproduct of the action of the "sweet" element of water.
</p>
<blockquote class="templatequote"><p>Animals and plants come into being
in earth and in liquid because there is water in earth, and air in
water, and in all air is vital heat so that in a sense all things are
full of soul. Therefore living things form quickly whenever this air and
vital heat are enclosed in anything. When they are so enclosed, the
corporeal liquids being heated, there arises as it were a frothy bubble.</p><div class="templatequotecite">— <cite>Aristotle, <i><a href="https://en.wikipedia.org/wiki/Generation_of_Animals" title="Generation of Animals">Generation of Animals</a></i>, Book III, Part 11</cite></div></blockquote>
<p>With varying degrees of observational confidence, Aristotle theorized
the spontaneous generation of a range of creatures from different sorts
of inanimate matter. The <a href="https://en.wikipedia.org/wiki/Testacea" title="Testacea">testaceans</a> (a genus which for Aristotle included <a href="https://en.wikipedia.org/wiki/Bivalvia" title="Bivalvia">bivalves</a>
and snails), for instance, were characterized by spontaneous generation
from mud, but differed based upon the precise material they grew in—for
example, <a href="https://en.wikipedia.org/wiki/Clam" title="Clam">clams</a> and <a href="https://en.wikipedia.org/wiki/Scallop" title="Scallop">scallops</a> in sand, <a href="https://en.wikipedia.org/wiki/Oyster" title="Oyster">oysters</a> in slime, and the <a href="https://en.wikipedia.org/wiki/Barnacle" title="Barnacle">barnacle</a> and the <a href="https://en.wikipedia.org/wiki/Limpet" title="Limpet">limpet</a> in the hollows of rocks.
</p>
<h3><span class="mw-headline" id="Latin_and_early_Christian_sources">Latin and early Christian sources</span></h3><p>Athenaeus dissented towards spontaneous generation, claiming that a variety of <a href="https://en.wikipedia.org/wiki/Anchovy" title="Anchovy">anchovy</a> did not generate from <a href="https://en.wikipedia.org/wiki/Roe" title="Roe">roe</a>, as Aristotle stated, but rather, from <a href="https://en.wikipedia.org/wiki/Sea_foam" title="Sea foam">sea foam</a>.
</p><p>As the dominant view of philosophers and thinkers continued to be in favour of spontaneous generation, some Christian <a href="https://en.wikipedia.org/wiki/Theology" title="Theology">theologians</a> accepted the view. The Berber theologian and philosopher <a href="https://en.wikipedia.org/wiki/Augustine_of_Hippo" title="Augustine of Hippo">Augustine of Hippo</a> discussed spontaneous generation in <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/City_of_God_(book)" title="City of God (book)">The City of God</a></i> and <i>The Literal Meaning of Genesis</i>, citing Biblical passages such as "Let the waters bring forth abundantly the moving creature that hath life" (<a class="extiw" href="https://en.wikisource.org/wiki/Bible_(King_James)/Genesis#1:20" title="s:Bible (King James)/Genesis">Genesis 1:20</a>) as decrees that would enable ongoing creation.
</p>
<h2><span class="mw-headline" id="Middle_Ages">Middle Ages</span></h2><div class="thumb tmulti tright"><div class="thumbinner multiimageinner"><div class="trow"><div class="tsingle"><div class="thumbimage"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Barnacle_Geese_Fac_simile_of_an_Engraving_on_Wood_from_the_Cosmographie_Universelle_of_Munster_folio_Basle_1552.png"><img alt="" class="mw-file-element" data-file-height="714" data-file-width="884" height="323" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Barnacle_Geese_Fac_simile_of_an_Engraving_on_Wood_from_the_Cosmographie_Universelle_of_Munster_folio_Basle_1552.png/115px-Barnacle_Geese_Fac_simile_of_an_Engraving_on_Wood_from_the_Cosmographie_Universelle_of_Munster_folio_Basle_1552.png" width="400" /></a></span></div><div class="thumbcaption">Barnacles turning into geese, in the 1552 <i><a href="https://en.wikipedia.org/wiki/Cosmographia_(Sebastian_M%C3%BCnster)" title="Cosmographia (Sebastian Münster)">Cosmographia</a></i></div><div class="thumbcaption"><i> </i></div></div><div class="tsingle"><div class="thumbimage"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Pollicipes_pollicipes.jpg"><img alt="" class="mw-file-element" data-file-height="2425" data-file-width="3233" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Pollicipes_pollicipes.jpg/124px-Pollicipes_pollicipes.jpg" width="400" /></a></span></div><div class="thumbcaption">The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pollicipes_cornucopia" title="Pollicipes cornucopia">goose barnacle</a></div><div class="thumbcaption"> </div></div><div class="tsingle"><div class="thumbimage"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Branta_leucopsis.jpg"><img alt="" class="mw-file-element" data-file-height="1024" data-file-width="1544" height="266" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Branta_leucopsis.jpg/140px-Branta_leucopsis.jpg" width="400" /></a></span></div><div class="thumbcaption">The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Branta_leucopsis" title="Branta leucopsis">barnacle goose</a></div><div class="thumbcaption"> </div></div></div><div class="trow" style="display: flex;"><div class="thumbcaption">In the <a href="https://en.wikipedia.org/wiki/Middle_Ages" title="Middle Ages">Middle Ages</a>, it was thought that the goose barnacle gave birth to the barnacle goose, supporting the <a href="https://en.wikipedia.org/wiki/Virgin_birth_of_Jesus" title="Virgin birth of Jesus">virgin birth of Jesus</a>.</div></div></div></div>
<p>From the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Decline_of_the_Roman_Empire" title="Decline of the Roman Empire">fall of the Roman Empire</a> in 5th century to the <a href="https://en.wikipedia.org/wiki/East%E2%80%93West_Schism" title="East–West Schism">East–West Schism</a> in 1054, the influence of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Greek_science" title="Greek science">Greek science</a>
declined, although spontaneous generation generally went unchallenged.
New descriptions were made. Of the beliefs, some had doctrinal
implications. In 1188, <a href="https://en.wikipedia.org/wiki/Gerald_of_Wales" title="Gerald of Wales">Gerald of Wales</a>, after having traveled in Ireland, argued that the <a href="https://en.wikipedia.org/wiki/Barnacle_goose_myth" title="Barnacle goose myth">barnacle goose myth</a> was evidence for the <a href="https://en.wikipedia.org/wiki/Virgin_birth_of_Jesus" title="Virgin birth of Jesus">virgin birth of Jesus</a>. Where the practice of fasting during <a href="https://en.wikipedia.org/wiki/Lent" title="Lent">Lent</a>
allowed fish, but prohibited fowl, the idea that the goose was in fact a
fish suggested that its consumption be permitted during Lent. The
practice was eventually prohibited by decree of <a href="https://en.wikipedia.org/wiki/Pope_Innocent_III" title="Pope Innocent III">Pope Innocent III</a> in 1215.
</p><p>After Aristotle’s works were reintroduced to Western Europe, they
were translated into Latin from the original Greek or Arabic. They
reached their greatest level of acceptance during the 13th century. With
the availability of Latin translations, the German philosopher <a href="https://en.wikipedia.org/wiki/Albertus_Magnus" title="Albertus Magnus">Albertus Magnus</a> and his student <a href="https://en.wikipedia.org/wiki/Thomas_Aquinas" title="Thomas Aquinas">Thomas Aquinas</a> raised Aristotelianism to its greatest prominence. Albert wrote a paraphrase of Aristotle, <i>De causis et processu universitatis</i>, in which he removed some commentaries by Arabic scholars and incorporated others.
The influential writings of Aquinas, on both the physical and
metaphysical, are predominantly Aristotelian, but show numerous other
influences.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Trees_that_generate_both_fishes_and_birds._Wellcome_M0005642.jpg"><img class="mw-file-element" data-file-height="4076" data-file-width="2575" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Trees_that_generate_both_fishes_and_birds._Wellcome_M0005642.jpg/170px-Trees_that_generate_both_fishes_and_birds._Wellcome_M0005642.jpg" width="253" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Claude_Duret" title="Claude Duret">Claude Duret</a>'s 1605 <i>Histoire admirable des plantes et herbes esmerueillables et miraculeuses en nature...</i> illustrated numerous supposed examples of spontaneous generation, such as this tree generating both fishes and birds</figcaption></figure>
<p>Spontaneous generation is described in literature as if it were a fact well into the <a href="https://en.wikipedia.org/wiki/Renaissance" title="Renaissance">Renaissance</a>. <a href="https://en.wikipedia.org/wiki/William_Shakespeare" title="William Shakespeare">Shakespeare</a> wrote of snakes and crocodiles forming from the mud of the <a href="https://en.wikipedia.org/wiki/Nile" title="Nile">Nile</a>:
</p>
<blockquote class="templatequote"><div class="poem">
<p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marcus_Aemilius_Lepidus_(triumvir)" title="Marcus Aemilius Lepidus (triumvir)">Lepidus</a>: You’ve strange serpents there?<br />
<a href="https://en.wikipedia.org/wiki/Mark_Antony" title="Mark Antony">Antony</a>: Ay, Lepidus.<br />
Lepidus: Your serpent of Egypt is bred now of your mud by the operation of your sun; so is your crocodile.<br />
Antony: They are so.
</p>
</div><p> Shakespeare: <i><a href="https://en.wikipedia.org/wiki/Antony_and_Cleopatra" title="Antony and Cleopatra">Antony and Cleopatra</a></i>: Act 2, scene 7</p></blockquote>
<p>The author of <i><a href="https://en.wikipedia.org/wiki/The_Compleat_Angler" title="The Compleat Angler">The Compleat Angler</a></i>, <a href="https://en.wikipedia.org/wiki/Izaak_Walton" title="Izaak Walton">Izaak Walton</a>
repeats the question of the origin of eels "as rats and mice, and many
other living creatures, are bred in Egypt, by the sun's heat when it
shines upon the overflowing of the river...". While the ancient question
of the origin of eels remained unanswered and the additional idea that
eels reproduced from corruption of age was mentioned, the spontaneous
generation of rats and mice stirred up no debate.
</p><p>The Dutch biologist and microscopist <a href="https://en.wikipedia.org/wiki/Jan_Swammerdam" title="Jan Swammerdam">Jan Swammerdam</a> rejected the concept that one animal could arise from another or from putrification by chance because it was <a href="https://en.wikipedia.org/wiki/Impiety" title="Impiety">impious</a>; he found the concept of spontaneous generation irreligious, and he associated it with <a href="https://en.wikipedia.org/wiki/Atheism" title="Atheism">atheism</a>.
</p>
<h2><span class="mw-headline" id="Previous_beliefs">Previous beliefs</span></h2><ul><li><a href="https://en.wikipedia.org/wiki/Frog" title="Frog">Frogs</a> were believed to have spontaneously generated from mud.</li><li><a href="https://en.wikipedia.org/wiki/Mouse" title="Mouse">Mice</a> were believed to become pregnant though the act of licking salt, or grew from the moisture of the earth.</li><li><a href="https://en.wikipedia.org/wiki/Barnacle_goose" title="Barnacle goose">Barnacle geese</a> were thought to have emerged from a <a href="https://en.wikipedia.org/wiki/Crustacean" title="Crustacean">crustacean</a>, the <a href="https://en.wikipedia.org/wiki/Goose_barnacle" title="Goose barnacle">goose barnacle</a> (see the <a href="https://en.wikipedia.org/wiki/Barnacle_goose_myth" title="Barnacle goose myth">barnacle goose myth</a>).</li><li><a href="https://en.wikipedia.org/wiki/Snake" title="Snake">Snakes</a> could generate from the marrow of the human <a href="https://en.wikipedia.org/wiki/Vertebral_column" title="Vertebral column">spine</a>, and had previously generated from the blood of <a href="https://en.wikipedia.org/wiki/Medusa" title="Medusa">Medusa</a>.</li><li><a href="https://en.wikipedia.org/wiki/Eel" title="Eel">Eels</a> had multiple stories. Aristotle claimed that <a href="https://en.wikipedia.org/wiki/Eel" title="Eel">eels</a> emerged from <a href="https://en.wikipedia.org/wiki/Earthworm" title="Earthworm">earthworms</a>, and were lacking in <a href="https://en.wikipedia.org/wiki/Sex" title="Sex">sex</a> and <a href="https://en.wikipedia.org/wiki/Milt" title="Milt">milt</a>, <a href="https://en.wikipedia.org/wiki/Spawn_(biology)" title="Spawn (biology)">spawn</a> and passages for these. Later authors dissented. The Roman author and natural historian <a href="https://en.wikipedia.org/wiki/Pliny_the_Elder" title="Pliny the Elder">Pliny the Elder</a>
did not argue against the anatomic limits of eels, but stated that eels
reproduce by budding, scraping themselves against rocks, liberating
particles that become eels. The Greek author <a href="https://en.wikipedia.org/wiki/Athenaeus" title="Athenaeus">Athenaeus</a> described eels as entwining and discharging a fluid which would settle on mud and generate life.</li><li><a href="https://en.wikipedia.org/wiki/Bookworm_(insect)" title="Bookworm (insect)">Bookworms</a> could generate from excessive wind. <a href="https://en.wikipedia.org/wiki/Vitruvius" title="Vitruvius">Vitruvius</a>, a <a href="https://en.wikipedia.org/wiki/Ancient_Rome" title="Ancient Rome">Roman</a> <a href="https://en.wikipedia.org/wiki/Architect" title="Architect">architect</a> and writer of the 1st century BCE, advised that to stop their generation, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Libraries" title="Libraries">libraries</a>
be placed facing eastwards to benefit from morning light, but not
towards the south or the west as those winds were particularly
offensive.</li><li><a href="https://en.wikipedia.org/wiki/Bee" title="Bee">Bees</a> were generated in decomposing cows, through a process known as <a href="https://en.wikipedia.org/wiki/Bugonia" title="Bugonia">bugonia</a>. <a href="https://en.wikipedia.org/wiki/Samson%27s_riddle" title="Samson's riddle">Samson's riddle</a> led some to believe they could also generate through the body of a <a href="https://en.wikipedia.org/wiki/Lion" title="Lion">lion</a>.</li><li><a href="https://en.wikipedia.org/wiki/Wasp" title="Wasp">Wasps</a> could be generated from decomposing horses.</li><li><a href="https://en.wikipedia.org/wiki/Cicada" title="Cicada">Cicada</a> were generated from the spittle of the <a href="https://en.wikipedia.org/wiki/Cuckoo" title="Cuckoo">cuckoo</a>.</li></ul>
<h2><span class="mw-headline" id="Experimental_approach">Experimental approach</span></h2><h3><span class="mw-headline" id="Early_tests">Early tests</span></h3><p>The Brussels physician <a href="https://en.wikipedia.org/wiki/Jan_Baptist_van_Helmont" title="Jan Baptist van Helmont">Jan Baptist van Helmont</a> described a recipe for mice (a piece of dirty cloth plus wheat for 21 days) and scorpions (<a href="https://en.wikipedia.org/wiki/Basil" title="Basil">basil</a>, placed between two bricks and left in sunlight). His notes suggest he may have attempted to do these things.
</p><p>Where Aristotle held that the <a href="https://en.wikipedia.org/wiki/Embryo" title="Embryo">embryo</a> was formed by a <a href="https://en.wikipedia.org/wiki/Coagulation" title="Coagulation">coagulation</a> in the <a href="https://en.wikipedia.org/wiki/Uterus" title="Uterus">uterus</a>, the English physician <a href="https://en.wikipedia.org/wiki/William_Harvey" title="William Harvey">William Harvey</a> showed by way of <a href="https://en.wikipedia.org/wiki/Dissection" title="Dissection">dissection</a> of <a href="https://en.wikipedia.org/wiki/Deer" title="Deer">deer</a> that there was no visible embryo during the first month. Although his work predated the <a href="https://en.wikipedia.org/wiki/Microscope" title="Microscope">microscope</a>, this led him to suggest that life came from invisible eggs. In the <a href="https://en.wikipedia.org/wiki/Book_frontispiece" title="Book frontispiece">frontispiece</a> of his 1651 book <i>Exercitationes de Generatione Animalium</i> (<i>Essays on the Generation of Animals</i>), he denied spontaneous generation with the motto <i>omnia ex ovo</i> ("everything from eggs").
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Illustration_of_Redi%27s_1668_experiment_to_refute_spontaneous_generation.svg"><img class="mw-file-element" data-file-height="376" data-file-width="690" height="218" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Illustration_of_Redi%27s_1668_experiment_to_refute_spontaneous_generation.svg/330px-Illustration_of_Redi%27s_1668_experiment_to_refute_spontaneous_generation.svg.png" width="400" /></a><figcaption>Illustration of Redi's 1668 experiment to refute spontaneous generation</figcaption></figure>
<p>The ancient beliefs were subjected to testing. In 1668, the Italian physician and parasitologist <a href="https://en.wikipedia.org/wiki/Francesco_Redi" title="Francesco Redi">Francesco Redi</a> challenged the idea that maggots arose spontaneously from rotting meat. In the first major <a href="https://en.wikipedia.org/wiki/Experiment" title="Experiment">experiment</a> to challenge spontaneous generation, he placed meat in a variety of sealed, open, and partially covered containers.
Realizing that the sealed containers were deprived of air, he used
"fine Naples veil", and observed no worms on the meat, but they appeared
on the cloth.
Redi used his experiments to support the preexistence theory put forth
by the Catholic Church at that time, which maintained that living things
originated from parents. In scientific circles Redi's work very soon had great influence, as evidenced in a letter from the English <a href="https://en.wikipedia.org/wiki/Natural_theology" title="Natural theology">natural theologian</a> <a href="https://en.wikipedia.org/wiki/John_Ray" title="John Ray">John Ray</a> in 1671 to members of the <a href="https://en.wikipedia.org/wiki/Royal_Society" title="Royal Society">Royal Society</a> of London, in which he calls the spontaneous generation of insects "unlikely".
</p><p><a href="https://en.wikipedia.org/wiki/Pier_Antonio_Micheli" title="Pier Antonio Micheli">Pier Antonio Micheli</a>, <abbr title="circa">c.</abbr><span style="white-space: nowrap;"> 1729</span>, observed that when fungal <a href="https://en.wikipedia.org/wiki/Spore" title="Spore">spores</a>
were placed on slices of melon, the same type of fungi were produced
that the spores came from, and from this observation he noted that fungi
did not arise from spontaneous generation.
</p><p>In 1745, <a href="https://en.wikipedia.org/wiki/John_Needham" title="John Needham">John Needham</a> performed a series of experiments on boiled <a href="https://en.wikipedia.org/wiki/Broth" title="Broth">broths</a>.
Believing that boiling would kill all living things, he showed that
when sealed right after boiling, the broths would cloud, allowing the
belief in spontaneous generation to persist. His studies were rigorously
scrutinized by his peers, and many of them agreed.
</p><p><a href="https://en.wikipedia.org/wiki/Lazzaro_Spallanzani" title="Lazzaro Spallanzani">Lazzaro Spallanzani</a>
modified the Needham experiment in 1768, where he attempted to exclude
the possibility of introducing a contaminating factor between boiling
and sealing. His technique involved boiling the broth in a sealed
container with the air partially <a href="https://en.wikipedia.org/wiki/Vacuum" title="Vacuum">evacuated</a>
to prevent explosions. Although he did not see growth, the exclusion of
air left the question of whether air was an essential factor in
spontaneous generation. But attitudes were changing; by the start of the 19th century, a scientist such as <a href="https://en.wikipedia.org/wiki/Joseph_Priestley" title="Joseph Priestley">Joseph Priestley</a>
could write that "There is nothing in modern philosophy that appears to
me so extraordinary, as the revival of what has long been considered as
the exploded doctrine of equivocal, or, as Dr. Darwin calls it,
spontaneous generation."
</p><p>In 1837, <a href="https://en.wikipedia.org/wiki/Charles_Cagniard_de_la_Tour" title="Charles Cagniard de la Tour">Charles Cagniard de la Tour</a>, a physicist, and <a href="https://en.wikipedia.org/wiki/Theodor_Schwann" title="Theodor Schwann">Theodor Schwann</a>, one of the founders of cell theory, published their independent discovery of <a href="https://en.wikipedia.org/wiki/Yeast" title="Yeast">yeast</a> in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alcoholic_fermentation" title="Alcoholic fermentation">alcoholic fermentation</a>. They used the microscope to examine foam left over from the process of <a href="https://en.wikipedia.org/wiki/Brewing" title="Brewing">brewing</a> beer. Where the Dutch microscopist <a href="https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek" title="Antonie van Leeuwenhoek">Antonie van Leeuwenhoek</a> described "small spheroid globules", they observed yeast cells undergo <a href="https://en.wikipedia.org/wiki/Cell_division" title="Cell division">cell division</a>.
Fermentation would not occur when sterile air or pure oxygen was
introduced if yeast were not present. This suggested that airborne <a href="https://en.wikipedia.org/wiki/Microorganism" title="Microorganism">microorganisms</a>, not spontaneous generation, was responsible.
</p><p>However, although the idea of spontaneous generation had been in
decline for nearly a century, its supporters did not abandon it all at
once. As <a href="https://en.wikipedia.org/wiki/James_Rennie_(naturalist)" title="James Rennie (naturalist)">James Rennie</a> wrote in 1838, despite Redi's experiments, "distinguished naturalists, such as <a href="https://en.wikipedia.org/wiki/Johann_Friedrich_Blumenbach" title="Johann Friedrich Blumenbach">Blumenbach</a>, <a href="https://en.wikipedia.org/wiki/Georges_Cuvier" title="Georges Cuvier">Cuvier</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jean_Baptiste_Bory_de_Saint-Vincent" title="Jean Baptiste Bory de Saint-Vincent">Bory de St. Vincent</a>, <a href="https://en.wikipedia.org/wiki/Robert_Brown_(botanist,_born_1773)" title="Robert Brown (botanist, born 1773)">R. Brown</a>, &c." continued to support the theory.
</p>
<h3><span class="mw-headline" id="Pasteur_and_Tyndall">Pasteur and Tyndall</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Experiment_Pasteur_English.jpg"><img class="mw-file-element" data-file-height="703" data-file-width="938" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Experiment_Pasteur_English.jpg/260px-Experiment_Pasteur_English.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a>'s
1859 experiment showed that a boiled nutrient broth did not give rise
spontaneously to new life, but that if direct access to air was
permitted, the broth decomposed, implying that small organisms (in
modern terms, <a href="https://en.wikipedia.org/wiki/Endospore" title="Endospore">microbial spores</a>) had fallen in and started to grow in the broth.</figcaption></figure>
<p><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a>'s 1859 experiment is widely seen as having settled the question of spontaneous generation. He boiled a meat broth in a <a href="https://en.wikipedia.org/wiki/Swan_neck_flask" title="Swan neck flask">swan neck flask</a>;
the bend in the neck of the flask prevented falling particles from
reaching the broth, while still allowing the free flow of air. The flask
remained free of growth for an extended period. When the flask was
turned so that particles could fall down the bends, the broth quickly
became clouded.
However, minority objections were persistent and not always
unreasonable, given that the experimental difficulties were far more
challenging than the popular accounts suggest. The investigations of the
Irish physician <a href="https://en.wikipedia.org/wiki/John_Tyndall" title="John Tyndall">John Tyndall</a>,
a correspondent of Pasteur and an admirer of his work, were decisive in
disproving spontaneous generation. All the same, Tyndall encountered
difficulties in dealing with <a href="https://en.wikipedia.org/wiki/Endospore" title="Endospore">microbial spores</a>, which were not well understood in his day. Like Pasteur, he boiled his <a href="https://en.wikipedia.org/wiki/Microbiological_culture" title="Microbiological culture">cultures</a> to sterilize them, and some types of bacterial spores can survive boiling. The <a href="https://en.wikipedia.org/wiki/Autoclave" title="Autoclave">autoclave</a>,
which eventually came into universal application in medical practice
and microbiology to sterilise equipment, was introduced after these
experiments.
</p><p>In 1862, the <a href="https://en.wikipedia.org/wiki/French_Academy_of_Sciences" title="French Academy of Sciences">French Academy of Sciences</a>
paid special attention to the issue, establishing a prize "to him who
by well-conducted experiments throws new light on the question of the
so-called spontaneous generation" and appointed a commission to judge
the winner. Pasteur and others used the term <i>biogenesis</i>
as the opposite of spontaneous generation, to mean that life was
generated only from other life. Pasteur's claim followed the German
physician <a href="https://en.wikipedia.org/wiki/Rudolf_Virchow" title="Rudolf Virchow">Rudolf Virchow</a>'s doctrine <i>Omnis cellula e cellula</i> ("all cells from cells"), itself derived from the work of <a href="https://en.wikipedia.org/wiki/Robert_Remak" title="Robert Remak">Robert Remak</a>.<sup> </sup>After Pasteur's 1859 experiment, the term "spontaneous generation" fell
out of favor. Experimentalists used a variety of terms for the study of
the origin of life from nonliving materials. <i>Heterogenesis</i> was
applied to the generation of living things from once-living organic
matter (such as boiled broths), and the English physiologist <a href="https://en.wikipedia.org/wiki/Henry_Charlton_Bastian" title="Henry Charlton Bastian">Henry Charlton Bastian</a> proposed the term <i>archebiosis</i> for life originating from non-living materials. Disliking the randomness and unpredictability implied by the term <i>spontaneous generation</i>, in 1870 Bastian coined the term <i>biogenesis</i> for the formation of life from nonliving matter. Soon thereafter, however, the English biologist <a href="https://en.wikipedia.org/wiki/Thomas_Henry_Huxley" title="Thomas Henry Huxley">Thomas Henry Huxley</a> proposed the term <i>abiogenesis</i> for this same process, and adopted <i>biogenesis</i> for the process by which life arises from existing life.</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-61451897309469174172024-03-17T20:02:00.005-04:002024-03-17T20:02:28.931-04:00Vitalism<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Vitalism">https://en.wikipedia.org/wiki/Vitalism</a></div><div class="noprint" id="siteSub"><b> </b></div><div class="noprint" id="siteSub"><b>Vitalism</b> is a belief that starts from the premise that "living
organisms are fundamentally different from non-living entities because
they contain some non-physical element or are governed by different
principles than are inanimate things." Where vitalism explicitly invokes a vital principle, that element is often referred to as the "vital spark", "energy", "<i><a href="https://en.wikipedia.org/wiki/%C3%89lan_vital" title="Élan vital">élan vital</a></i>" (coined by vitalist <a href="https://en.wikipedia.org/wiki/Henri_Bergson" title="Henri Bergson">Henri Bergson</a>), "vital force", or "<i><b>vis vitalis</b></i>", which some equate with the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Soul_(spirit)" title="Soul (spirit)">soul</a>. In the 18th and 19th centuries, vitalism was <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alternatives_to_evolution_by_natural_selection" title="Alternatives to evolution by natural selection">discussed among biologists</a>,
between those who felt that the known mechanics of physics would
eventually explain the difference between life and non-life and
vitalists who argued that the processes of life could not be reduced to a
mechanistic process. Vitalist biologists such as <a href="https://en.wikipedia.org/wiki/Johannes_Reinke" title="Johannes Reinke">Johannes Reinke</a> proposed <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Testable" title="Testable">testable</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hypotheses" title="Hypotheses">hypotheses</a>
meant to show inadequacies with mechanistic explanations, but their
experiments failed to provide support for vitalism. Biologists now
consider vitalism in this sense to have been refuted by <a href="https://en.wikipedia.org/wiki/Scientific_evidence" title="Scientific evidence">empirical evidence</a>, and hence regard it either as a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Superseded_scientific_theories" title="Superseded scientific theories">superseded scientific theory</a>, or, since the mid-20th century, as a <a href="https://en.wikipedia.org/wiki/Pseudoscience" title="Pseudoscience">pseudoscience</a>.
</div></div></div><p>Vitalism has a long history in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Medical" title="Medical">medical</a> philosophies: many <a href="https://en.wikipedia.org/wiki/Traditional_medicine" title="Traditional medicine">traditional healing</a> practices posited that disease results from some imbalance in vital forces.
</p>
<h2><span class="mw-headline" id="History">History</span></h2><h3><span class="mw-headline" id="Ancient_times">Ancient times</span></h3><p>The
notion that bodily functions are due to a vitalistic principle existing
in all living creatures has roots going back at least to <a href="https://en.wikipedia.org/wiki/Ancient_Egypt" title="Ancient Egypt">ancient Egypt</a>. In <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Greek_philosophy" title="Greek philosophy">Greek philosophy</a>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Milesian_school" title="Milesian school">Milesian school</a> proposed natural explanations <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Deductive_argument" title="Deductive argument">deduced</a> from <a href="https://en.wikipedia.org/wiki/Materialism" title="Materialism">materialism</a> and <a href="https://en.wikipedia.org/wiki/Mechanism_(philosophy)" title="Mechanism (philosophy)">mechanism</a>. However, by the time of <a href="https://en.wikipedia.org/wiki/Lucretius" title="Lucretius">Lucretius</a>, this account was supplemented, (for example, by the unpredictable <i><a href="https://en.wikipedia.org/wiki/Clinamen" title="Clinamen">clinamen</a></i> of <a href="https://en.wikipedia.org/wiki/Epicurus" title="Epicurus">Epicurus</a>), and in <a href="https://en.wikipedia.org/wiki/Stoic_physics" title="Stoic physics">Stoic physics</a>, the <i><a href="https://en.wikipedia.org/wiki/Pneuma" title="Pneuma">pneuma</a></i> assumed the role of <i><a href="https://en.wikipedia.org/wiki/Logos" title="Logos">logos</a></i>. <a href="https://en.wikipedia.org/wiki/Galen" title="Galen">Galen</a> believed the lungs draw <i>pneuma</i> from the air, which the blood communicates throughout the body.
</p>
<h3><span class="mw-headline" id="Medieval">Medieval</span></h3><p>In Europe, medieval physics was influenced by the idea of <i>pneuma</i>, helping to shape later <a href="https://en.wikipedia.org/wiki/Aether_theories" title="Aether theories">aether theories</a>.
</p>
<h3><span class="mw-headline" id="Early_modern">Early modern</span></h3><p>Vitalists included English anatomist <a href="https://en.wikipedia.org/wiki/Francis_Glisson" title="Francis Glisson">Francis Glisson</a> (1597–1677) and the Italian doctor <a href="https://en.wikipedia.org/wiki/Marcello_Malpighi" title="Marcello Malpighi">Marcello Malpighi</a> (1628–1694). <a href="https://en.wikipedia.org/wiki/Caspar_Friedrich_Wolff" title="Caspar Friedrich Wolff">Caspar Friedrich Wolff</a> (1733–1794) is considered to be the father of <a href="https://en.wikipedia.org/wiki/Epigenesis_(biology)" title="Epigenesis (biology)">epigenesis</a> in <a href="https://en.wikipedia.org/wiki/Embryology" title="Embryology">embryology</a>,
that is, he marks the point when embryonic development began to be
described in terms of the proliferation of cells rather than the
incarnation of a preformed soul. However, this degree of empirical
observation was not matched by a mechanistic philosophy: in his <i><a class="new" href="https://en.wikipedia.org/w/index.php?title=Theoria_Generationis&action=edit&redlink=1" title="Theoria Generationis (page does not exist)">Theoria Generationis</a></i> (1759), he tried to explain the emergence of the organism by the actions of a <i>vis essentialis</i> (an organizing, formative force). <a href="https://en.wikipedia.org/wiki/Carl_Reichenbach" title="Carl Reichenbach">Carl Reichenbach</a> (1788–1869) later developed the theory of <a href="https://en.wikipedia.org/wiki/Odic_force" title="Odic force">Odic force</a>, a form of life-energy that permeates living things.
</p><p>In the 17th century, modern science responded to <a href="https://en.wikipedia.org/wiki/Isaac_Newton" title="Isaac Newton">Newton</a>'s <a href="https://en.wikipedia.org/wiki/Action_at_a_distance" title="Action at a distance">action at a distance</a> and the mechanism of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cartesian_dualism" title="Cartesian dualism">Cartesian dualism</a>
with vitalist theories: that whereas the chemical transformations
undergone by non-living substances are reversible, so-called "organic"
matter is permanently altered by chemical transformations (such as
cooking).
</p><p>As worded by <a href="https://en.wikipedia.org/wiki/Charles_Birch" title="Charles Birch">Charles Birch</a> and <a href="https://en.wikipedia.org/wiki/John_B._Cobb" title="John B. Cobb">John B. Cobb</a>, "the claims of the vitalists came to the fore again" in the 18th century: "<a href="https://en.wikipedia.org/wiki/Georg_Ernst_Stahl" title="Georg Ernst Stahl">Georg Ernst Stahl</a>'s followers were active as were others, such as the physician genius <a href="https://en.wikipedia.org/wiki/Xavier_Bichat" title="Xavier Bichat">Francis Xavier Bichat</a> of the Hotel Dieu." However, "Bichat moved from the tendency typical of the French vitalistic tradition to progressively free himself from <a href="https://en.wikipedia.org/wiki/Metaphysics" title="Metaphysics">metaphysics</a> in order to combine with hypotheses and theories which accorded to the scientific criteria of physics and chemistry." <a href="https://en.wikipedia.org/wiki/John_Hunter_(surgeon)" title="John Hunter (surgeon)">John Hunter</a> recognised "a 'living principle' in addition to mechanics."
</p><p><a href="https://en.wikipedia.org/wiki/Johann_Friedrich_Blumenbach" title="Johann Friedrich Blumenbach">Johann Friedrich Blumenbach</a> was influential in establishing epigenesis in the life sciences in 1781 with his publication of <i>Über den Bildungstrieb und das Zeugungsgeschäfte</i>. Blumenbach cut up freshwater <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydra_(zoology)" title="Hydra (zoology)">Hydra</a></i> and established that the removed parts would regenerate. He inferred the presence of a "formative drive" (<i>Bildungstrieb</i>) in living matter. But he pointed out that this name,
</p>
<blockquote class="templatequote"><p>like names applied to every other
kind of vital power, of itself, explains nothing: it serves merely to
designate a peculiar power formed by the combination of the mechanical
principle with that which is susceptible of modification.</p></blockquote>
<h3><span class="mw-headline" id="19th_century">19th century</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alternatives_to_Darwinism" title="Alternatives to Darwinism">Alternatives to Darwinism</a></div>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Sample_of_Urea.jpg"><img class="mw-file-element" data-file-height="2894" data-file-width="2551" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Sample_of_Urea.jpg/220px-Sample_of_Urea.jpg" width="352" /></a><figcaption>The synthesis of <a href="https://en.wikipedia.org/wiki/Urea" title="Urea">urea</a> in the early 19th century from <a href="https://en.wikipedia.org/wiki/Inorganic_chemistry" title="Inorganic chemistry">inorganic compounds</a> was <a href="https://en.wikipedia.org/wiki/Counterevidence" title="Counterevidence">counterevidence</a> for the vitalist hypothesis that only organisms could make the components of living things.</figcaption></figure>
<p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/J%C3%B6ns_Jakob_Berzelius" title="Jöns Jakob Berzelius">Jöns Jakob Berzelius</a>, one of the early 19th century founders of modern <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, argued that a regulative force must exist within living matter to maintain its functions. Berzelius contended that compounds could be distinguished by whether they required any organisms in their <a href="https://en.wikipedia.org/wiki/Biosynthesis" title="Biosynthesis">synthesis</a> (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Organic_compounds" title="Organic compounds">organic compounds</a>) or whether they did not (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Inorganic_compounds" title="Inorganic compounds">inorganic compounds</a>). Vitalist chemists predicted that organic materials could not be synthesized from inorganic components, but <a href="https://en.wikipedia.org/wiki/Friedrich_W%C3%B6hler" title="Friedrich Wöhler">Friedrich Wöhler</a> synthesised <a href="https://en.wikipedia.org/wiki/Urea" title="Urea">urea</a> from inorganic components in 1828. However, contemporary accounts do not support the common belief that vitalism died when Wöhler made urea. This <i>Wöhler Myth</i>,
as historian Peter Ramberg called it, originated from a popular history
of chemistry published in 1931, which, "ignoring all pretense of
historical accuracy, turned Wöhler into a crusader who made attempt
after attempt to synthesize a natural product that would refute vitalism
and lift the veil of ignorance, until 'one afternoon the miracle
happened'".
</p><p>Between 1833 and 1844, <a href="https://en.wikipedia.org/wiki/Johannes_Peter_M%C3%BCller" title="Johannes Peter Müller">Johannes Peter Müller</a> wrote a book on <a href="https://en.wikipedia.org/wiki/Physiology" title="Physiology">physiology</a> called <i>Handbuch der Physiologie</i>,
which became the leading textbook in the field for much of the
nineteenth century. The book showed Müller's commitments to vitalism; he
questioned why organic matter differs from inorganic, then proceeded to
chemical analyses of the blood and lymph. He describes in detail the
circulatory, lymphatic, respiratory, digestive, endocrine, nervous, and
sensory systems in a wide variety of animals but explains that the
presence of a <a href="https://en.wikipedia.org/wiki/Soul" title="Soul">soul</a>
makes each organism an indivisible whole. He claimed that the behaviour
of light and sound waves showed that living organisms possessed a
life-energy for which physical laws could never fully account.
</p>
<figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg"><img class="mw-file-element" data-file-height="2532" data-file-width="2082" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg/170px-Albert_Edelfelt_-_Louis_Pasteur_-_1885.jpg" width="329" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> argued that only life could catalyse <a href="https://en.wikipedia.org/wiki/Fermentation" title="Fermentation">fermentation</a>. Painting by <a href="https://en.wikipedia.org/wiki/Albert_Edelfelt" title="Albert Edelfelt">Albert Edelfelt</a>, 1885</figcaption></figure>
<p><a href="https://en.wikipedia.org/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> (1822–1895) after his famous rebuttal of <a href="https://en.wikipedia.org/wiki/Spontaneous_generation" title="Spontaneous generation">spontaneous generation</a>,
performed several experiments that he felt supported vitalism.
According to Bechtel, Pasteur "fitted fermentation into a more general
programme describing special reactions that only occur in living
organisms. These are irreducibly vital phenomena." Rejecting the claims
of Berzelius, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Liebig" title="Liebig">Liebig</a>, <a href="https://en.wikipedia.org/wiki/Moritz_Traube" title="Moritz Traube">Traube</a>
and others that fermentation resulted from chemical agents or catalysts
within cells, Pasteur concluded that fermentation was a "vital action".
</p>
<h3><span class="mw-headline" id="20th_century">20th century</span></h3><p><a href="https://en.wikipedia.org/wiki/Hans_Driesch" title="Hans Driesch">Hans Driesch</a> (1867–1941) interpreted his experiments as showing that life is not run by physicochemical laws.
His main argument was that when one cuts up an embryo after its first
division or two, each part grows into a complete adult. Driesch's
reputation as an experimental biologist deteriorated as a result of his
vitalistic theories, which scientists have seen since his time as
pseudoscience. Vitalism is a superseded scientific hypothesis, and the term is sometimes used as a <a href="https://en.wikipedia.org/wiki/Pejorative" title="Pejorative">pejorative</a> <a href="https://en.wikipedia.org/wiki/Epithet" title="Epithet">epithet</a>. <a href="https://en.wikipedia.org/wiki/Ernst_Mayr" title="Ernst Mayr">Ernst Mayr</a> (1904–2005) wrote:
</p>
<blockquote class="templatequote"><p>It would be ahistorical to ridicule
vitalists. When one reads the writings of one of the leading vitalists
like Driesch one is forced to agree with him that many of the basic
problems of biology simply cannot be solved by a philosophy as that of
Descartes, in which the organism is simply considered a machine... The
logic of the critique of the vitalists was impeccable.</p></blockquote>
<blockquote class="templatequote"><p>Vitalism has become so disreputable
a belief in the last fifty years that no biologist alive today would
want to be classified as a vitalist. Still, the remnants of vitalist
thinking can be found in the work of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alistair_Hardy" title="Alistair Hardy">Alistair Hardy</a>, <a href="https://en.wikipedia.org/wiki/Sewall_Wright" title="Sewall Wright">Sewall Wright</a>, and <a href="https://en.wikipedia.org/wiki/Charles_Birch" title="Charles Birch">Charles Birch</a>, who seem to believe in some sort of nonmaterial principle in organisms.</p></blockquote>
<p>Other vitalists included <a href="https://en.wikipedia.org/wiki/Johannes_Reinke" title="Johannes Reinke">Johannes Reinke</a> and <a href="https://en.wikipedia.org/wiki/Oscar_Hertwig" title="Oscar Hertwig">Oscar Hertwig</a>. Reinke used the word <i>neovitalism</i>
to describe his work, claiming that it would eventually be verified
through experimentation, and that it was an improvement over the other
vitalistic theories. The work of Reinke influenced <a href="https://en.wikipedia.org/wiki/Carl_Jung" title="Carl Jung">Carl Jung</a>.
</p><p><a href="https://en.wikipedia.org/wiki/John_Scott_Haldane" title="John Scott Haldane">John Scott Haldane</a> adopted an anti-mechanist approach to biology and an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Idealist" title="Idealist">idealist</a> philosophy early on in his career. Haldane saw his work as a vindication of his belief that <a href="https://en.wikipedia.org/wiki/Teleology" title="Teleology">teleology</a> was an essential concept in biology. His views became widely known with his first book <i>Mechanism, life and personality</i> in 1913.
Haldane borrowed arguments from the vitalists to use against mechanism;
however, he was not a vitalist. Haldane treated the organism as
fundamental to biology: "we perceive the organism as a self-regulating
entity", "every effort to analyze it into components that can be reduced
to a mechanical explanation violates this central experience". The work of Haldane was an influence on <a href="https://en.wikipedia.org/wiki/Organicism" title="Organicism">organicism</a>.
Haldane stated that a purely mechanist interpretation could not account
for the characteristics of life. Haldane wrote a number of books in
which he attempted to show the invalidity of both vitalism and mechanist
approaches to science. Haldane explained:
</p>
<blockquote class="templatequote"><p>We must find a different
theoretical basis of biology, based on the observation that all the
phenomena concerned tend towards being so coordinated that they express
what is normal for an adult organism.</p></blockquote>
<p>By 1931, biologists had "almost unanimously abandoned vitalism as an acknowledged belief."
</p>
<h2><span class="mw-headline" id="Emergentism">Emergentism</span></h2><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Emergentism" title="Emergentism">Emergentism</a></div>
<p>Contemporary science and engineering sometimes describe <a href="https://en.wikipedia.org/wiki/Emergence" title="Emergence">emergent processes</a>, in which the properties of a system cannot be fully described in terms of the properties of the constituents.
This may be because the properties of the constituents are not fully
understood, or because the interactions between the individual
constituents are important for the behavior of the system.
</p><p>Whether emergence should be grouped with traditional vitalist concepts is a matter of semantic controversy. According to Emmeche <i>et al.</i> (1997):
</p>
<blockquote class="templatequote"><p>On the one hand, many scientists
and philosophers regard emergence as having only a pseudo-scientific
status. On the other hand, new developments in physics, biology,
psychology, and cross-disciplinary fields such as cognitive science,
artificial life, and the study of non-linear dynamical systems have
focused strongly on the high level 'collective behaviour' of complex
systems, which is often said to be truly emergent, and the term is
increasingly used to characterize such systems.</p></blockquote>
<h2><span class="mw-headline" id="Mesmerism">Mesmerism</span></h2><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Animal_magnetism" title="Animal magnetism">Animal magnetism</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Franz_Anton_Mesmer.jpg"><img class="mw-file-element" data-file-height="1335" data-file-width="1000" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Franz_Anton_Mesmer.jpg/170px-Franz_Anton_Mesmer.jpg" width="300" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Franz_Mesmer" title="Franz Mesmer">Franz Mesmer</a> proposed the vitalist force of <i><a href="https://en.wikipedia.org/wiki/Animal_magnetism" title="Animal magnetism">magnétisme animal</a></i> in animals with breath.</figcaption></figure>
<p>A popular vitalist theory of the 18th century was "<a href="https://en.wikipedia.org/wiki/Animal_magnetism" title="Animal magnetism">animal magnetism</a>", in the theories of <a href="https://en.wikipedia.org/wiki/Franz_Mesmer" title="Franz Mesmer">Franz Mesmer</a> (1734–1815). However, the use of the (conventional) English term <i>animal magnetism</i> to translate Mesmer's <b>magnétisme animal</b> can be misleading for three reasons:
</p>
<ul><li>Mesmer chose his term to clearly distinguish his variant of <i>magnetic</i> force from those referred to, at that time, as <i>mineral magnetism</i>, <i>cosmic magnetism</i> and <i>planetary magnetism</i>.</li><li>Mesmer felt that this particular force/power only resided in the bodies of humans and animals.</li><li>Mesmer chose the word "<i>animal</i>," for its root meaning (from Latin <i>animus</i>="breath")
specifically to identify his force as a quality that belonged to all
creatures with breath; viz., the animate beings: humans <b>and</b> animals.</li></ul>
<p>Mesmer's ideas became so influential that King <a href="https://en.wikipedia.org/wiki/Louis_XVI" title="Louis XVI">Louis XVI</a> of France appointed two commissions to investigate <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mesmerism" title="Mesmerism">mesmerism</a>; one was led by <a href="https://en.wikipedia.org/wiki/Joseph-Ignace_Guillotin" title="Joseph-Ignace Guillotin">Joseph-Ignace Guillotin</a>, the other, led by <a href="https://en.wikipedia.org/wiki/Benjamin_Franklin" title="Benjamin Franklin">Benjamin Franklin</a>, included <a href="https://en.wikipedia.org/wiki/Jean_Sylvain_Bailly" title="Jean Sylvain Bailly">Bailly</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lavoisier" title="Lavoisier">Lavoisier</a>. The commissioners learned about Mesmeric theory, and saw its patients fall into fits and <a href="https://en.wikipedia.org/wiki/Trance" title="Trance">trances</a>.
In Franklin's garden, a patient was led to each of five trees, one of
which had been "mesmerized"; he hugged each in turn to receive the
"vital fluid," but fainted at the foot of a 'wrong' one. At Lavoisier's
house, four normal cups of water were held before a "sensitive" woman;
the fourth produced convulsions, but she calmly swallowed the mesmerized
contents of a fifth, believing it to be plain water. The commissioners
concluded that "the fluid without imagination is powerless, whereas
imagination without the fluid can produce the effects of the fluid."
</p>
<h2><span class="mw-headline" id="Medical_philosophies">Medical philosophies</span></h2><p>Vitalism has a long history in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Medical" title="Medical">medical</a> philosophies: many <a href="https://en.wikipedia.org/wiki/Traditional_medicine" title="Traditional medicine">traditional healing</a> practices posited that disease results from some imbalance in vital forces. In the Western tradition founded by <a href="https://en.wikipedia.org/wiki/Hippocrates" title="Hippocrates">Hippocrates</a>, these vital forces were associated with the <a href="https://en.wikipedia.org/wiki/Four_temperaments" title="Four temperaments">four temperaments</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/The_four_humours" title="The four humours">humours</a>; Eastern traditions posited an imbalance or blocking of <a href="https://en.wikipedia.org/wiki/Qi" title="Qi">qi</a> or <a href="https://en.wikipedia.org/wiki/Prana" title="Prana">prana</a>. One example of a similar notion in Africa is the <a href="https://en.wikipedia.org/wiki/Yoruba_people" title="Yoruba people">Yoruba</a> concept of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ase_(Yoruba)" title="Ase (Yoruba)">ase</a>. Today forms of vitalism continue to exist as philosophical positions or as tenets in some religious traditions.
</p><p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Complementary_and_alternative_medicine" title="Complementary and alternative medicine">Complementary and alternative medicine</a> therapies include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Energy_therapy" title="Energy therapy">energy therapies</a>, associated with vitalism, especially biofield therapies such as <a href="https://en.wikipedia.org/wiki/Therapeutic_touch" title="Therapeutic touch">therapeutic touch</a>, <a href="https://en.wikipedia.org/wiki/Reiki" title="Reiki">Reiki</a>, external <a href="https://en.wikipedia.org/wiki/Qi" title="Qi">qi</a>, <a href="https://en.wikipedia.org/wiki/Chakra" title="Chakra">chakra</a> healing and SHEN therapy. In these therapies, the "<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Subtle_energy" title="Subtle energy">subtle energy</a>"
field of a patient is manipulated by a practitioner. The subtle energy
is held to exist beyond the electromagnetic energy produced by the heart
and brain. Beverly Rubik describes the biofield as a "complex, dynamic,
extremely weak EM field within and around the human body...."
</p><p>The founder of <a href="https://en.wikipedia.org/wiki/Homeopathy" title="Homeopathy">homeopathy</a>, <a href="https://en.wikipedia.org/wiki/Samuel_Hahnemann" title="Samuel Hahnemann">Samuel Hahnemann</a>,
promoted an immaterial, vitalistic view of disease: "...they are solely
spirit-like (dynamic) derangements of the spirit-like power (the vital
principle) that animates the human body." The view of disease as a
dynamic disturbance of the immaterial and dynamic vital force is taught
in many homeopathic colleges and constitutes a fundamental principle for
many contemporary practising homeopaths.
</p>
<h2><span class="mw-headline" id="Criticism">Criticism</span></h2><figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Pierre_Mignard_-_Portrait_de_Jean-Baptiste_Poquelin_dit_Moli%C3%A8re_(1622-1673)_-_Google_Art_Project_(cropped).jpg"><img class="mw-file-element" data-file-height="4214" data-file-width="3716" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d1/Pierre_Mignard_-_Portrait_de_Jean-Baptiste_Poquelin_dit_Moli%C3%A8re_%281622-1673%29_-_Google_Art_Project_%28cropped%29.jpg/170px-Pierre_Mignard_-_Portrait_de_Jean-Baptiste_Poquelin_dit_Moli%C3%A8re_%281622-1673%29_-_Google_Art_Project_%28cropped%29.jpg" width="352" /></a><figcaption>The 17th century French playwright <a href="https://en.wikipedia.org/wiki/Moli%C3%A8re" title="Molière">Molière</a> mocked vitalism in his 1673 play <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Le_Malade_imaginaire" title="Le Malade imaginaire">Le Malade imaginaire</a></i>.</figcaption></figure>
<p>Vitalism has sometimes been criticized as <a href="https://en.wikipedia.org/wiki/Begging_the_question" title="Begging the question">begging the question</a> by inventing a name. <a href="https://en.wikipedia.org/wiki/Moli%C3%A8re" title="Molière">Molière</a> had famously parodied this fallacy in <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Le_Malade_imaginaire" title="Le Malade imaginaire">Le Malade imaginaire</a></i>, where a quack "answers" the question of "Why does <a href="https://en.wikipedia.org/wiki/Opium" title="Opium">opium</a> cause sleep?" with "Because of its <b>dormitive virtue</b> (i.e., <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Soporific" title="Soporific">soporific</a> power)." <a href="https://en.wikipedia.org/wiki/Thomas_Henry_Huxley" title="Thomas Henry Huxley">Thomas Henry Huxley</a> compared vitalism to stating that water is the way it is because of its "aquosity". His grandson <a href="https://en.wikipedia.org/wiki/Julian_Huxley" title="Julian Huxley">Julian Huxley</a> in 1926 compared "vital force" or <i>élan vital</i> to explaining a railroad locomotive's operation by its <i>élan locomotif</i> ("locomotive force").
</p><p>Another criticism is that vitalists have failed to rule out mechanistic explanations. This is rather obvious in retrospect for <a href="https://en.wikipedia.org/wiki/Organic_chemistry" title="Organic chemistry">organic chemistry</a> and <a href="https://en.wikipedia.org/wiki/Developmental_biology" title="Developmental biology">developmental biology</a>, but the criticism goes back at least a century. In 1912, <a href="https://en.wikipedia.org/wiki/Jacques_Loeb" title="Jacques Loeb">Jacques Loeb</a> published <i>The Mechanistic Conception of Life</i>, in which he described experiments on how a sea urchin could have a pin for its father, as <a href="https://en.wikipedia.org/wiki/Bertrand_Russell" title="Bertrand Russell">Bertrand Russell</a> put it (<i>Religion and Science</i>). He offered this challenge:
</p>
<dl><dd>"... we must either succeed in producing living matter
artificially, or we must find the reasons why this is impossible."
(pp. 5–6)</dd></dl>
<p>Loeb addressed vitalism more explicitly:
</p>
<dl><dd>"It is, therefore, unwarranted to continue the statement that in
addition to the acceleration of oxidations the beginning of individual
life is determined by the entrance of a metaphysical "life principle"
into the egg; and that death is determined, aside from the cessation of
oxidations, by the departure of this "principle" from the body. In the
case of the evaporation of water we are satisfied with the explanation
given by the kinetic theory of gases and do not demand that to repeat a
well-known jest of Huxley the disappearance of the "aquosity" be also
taken into consideration." (pp. 14–15)</dd></dl>
<p>Bechtel states that vitalism "is often viewed as <a href="https://en.wikipedia.org/wiki/Falsifiability" title="Falsifiability">unfalsifiable</a>, and therefore a pernicious metaphysical doctrine."
For many scientists, "vitalist" theories were unsatisfactory "holding
positions" on the pathway to mechanistic understanding. In 1967, <a href="https://en.wikipedia.org/wiki/Francis_Crick" title="Francis Crick">Francis Crick</a>, the co-discoverer of the structure of <a href="https://en.wikipedia.org/wiki/DNA" title="DNA">DNA</a>,
stated "And so to those of you who may be vitalists I would make this
prophecy: what everyone believed yesterday, and you believe today, only <a href="https://en.wikipedia.org/wiki/Crank_(person)" title="Crank (person)">cranks</a> will believe tomorrow."
</p><p>While many vitalistic theories have in fact been falsified, notably Mesmerism, the <a href="https://en.wikipedia.org/wiki/Pseudoscience" title="Pseudoscience">pseudoscientific</a> retention of untested and <a href="https://en.wikipedia.org/wiki/Testability" title="Testability">untestable</a> theories continues to this day. <a href="https://en.wikipedia.org/wiki/Alan_Sokal" title="Alan Sokal">Alan Sokal</a>
published an analysis of the wide acceptance among professional nurses
of "scientific theories" of spiritual healing. (Pseudoscience and
Postmodernism: Antagonists or Fellow-Travelers?). Use of a technique called <a href="https://en.wikipedia.org/wiki/Therapeutic_touch" title="Therapeutic touch">therapeutic touch</a>
was especially reviewed by Sokal, who concluded, "nearly all the
pseudoscientific systems to be examined in this essay are based
philosophically on vitalism" and added that "Mainstream science has
rejected vitalism since at least the 1930s, for a plethora of good
reasons that have only become stronger with time."
</p><p>Joseph C. Keating, Jr. discusses vitalism's past and present roles in <a href="https://en.wikipedia.org/wiki/Chiropractic" title="Chiropractic">chiropractic</a> and calls vitalism "a form of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bio-theology" title="Bio-theology">bio-theology</a>." He further explains that:
</p>
<dl><dd>"Vitalism is that rejected tradition in biology which proposes
that life is sustained and explained by an unmeasurable, intelligent
force or energy. The supposed effects of vitalism are the manifestations
of life itself, which in turn are the basis for inferring the concept
in the first place. This circular reasoning offers pseudo-explanation,
and may deceive us into believing we have explained some aspect of
biology when in fact we have only labeled our ignorance. 'Explaining an
unknown (life) with an unknowable (Innate),' suggests chiropractor
Joseph Donahue, 'is absurd'."</dd></dl>
<p>Keating views vitalism as incompatible with scientific thinking:
</p>
<dl><dd>"Chiropractors are not unique in recognizing a tendency and
capacity for self-repair and auto-regulation of human physiology. But we
surely stick out like a sore thumb among professions which claim to be
scientifically based by our unrelenting commitment to vitalism. So long
as we propound the 'One cause, one cure' rhetoric of Innate, we should
expect to be met by ridicule from the wider health science community.
Chiropractors can't have it both ways. Our theories cannot be both
dogmatically held vitalistic constructs and be scientific at the same
time. The purposiveness, consciousness and rigidity of the Palmers'
Innate should be rejected."</dd></dl>
<p>Keating also mentions Skinner's viewpoint:
</p>
<dl><dd>"Vitalism has many faces and has sprung up in many areas of scientific inquiry. Psychologist <a class="mw-redirect" href="https://en.wikipedia.org/wiki/B.F._Skinner" title="B.F. Skinner">B.F. Skinner</a>,
for example, pointed out the irrationality of attributing behavior to
mental states and traits. Such 'mental way stations,' he argued, amount
to excess theoretical baggage which fails to advance cause-and-effect
explanations by substituting an unfathomable psychology of 'mind'."</dd></dl>
<p>According to Williams, "[t]oday, vitalism is one of the ideas that
form the basis for many pseudoscientific health systems that claim that
illnesses are caused by a disturbance or imbalance of the body's vital
force."
"Vitalists claim to be scientific, but in fact they reject the
scientific method with its basic postulates of cause and effect and of
provability. They often regard subjective experience to be more valid
than objective material reality."
</p><p><a href="https://en.wikipedia.org/wiki/Victor_J._Stenger" title="Victor J. Stenger">Victor Stenger</a> states that the term "bioenergetics" "is applied in biochemistry to refer to the readily measurable <a href="https://en.wikipedia.org/wiki/Biological_thermodynamics" title="Biological thermodynamics">exchanges of energy</a>
within organisms, and between organisms and the environment, which
occur by normal physical and chemical processes. This is not, however,
what the new vitalists have in mind. They imagine the <a href="https://en.wikipedia.org/wiki/Energy_(esotericism)" title="Energy (esotericism)">bioenergetic</a> field as a holistic living force that goes beyond reductionist physics and chemistry."
</p><p>Such a field is sometimes explained as electromagnetic, though some advocates also make confused appeals to quantum physics. Joanne Stefanatos states that "The principles of energy medicine originate in quantum physics." Stenger
offers several explanations as to why this line of reasoning may be
misplaced. He explains that energy exists in discrete packets called
quanta. Energy fields are composed of their component parts and so only
exist when quanta are present. Therefore, energy fields are not
holistic, but are rather a system of discrete parts that must obey the
laws of physics. This also means that energy fields are not
instantaneous. These facts of quantum physics place limitations on the
infinite, continuous field that is used by some theorists to describe
so-called "human energy fields".
Stenger continues, explaining that the effects of EM forces have been
measured by physicists as accurately as one part in a billion and there
is yet to be any evidence that living organisms emit a unique field.
</p><p>Vitalistic thinking has been identified in the naive biological
theories of children: "Recent experimental results show that a majority
of preschoolers tend to choose vitalistic explanations as most
plausible. Vitalism, together with other forms of intermediate
causality, constitute unique causal devices for naive biology as a core
domain of thought."<sup class="reference" id="cite_ref-45"><a href="https://en.wikipedia.org/wiki/Vitalism#cite_note-45"></a></sup></p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-38814449727753621692024-03-17T19:01:00.003-04:002024-03-17T19:01:21.594-04:00Seaweed fertiliser<div class="vector-column-end">
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<p><b>Seaweed fertiliser</b> (or <b>fertilizer</b>) is <a href="https://en.wikipedia.org/wiki/Organic_fertilizer" title="Organic fertilizer">organic fertilizer</a> made from <a href="https://en.wikipedia.org/wiki/Seaweed" title="Seaweed">seaweed</a>
that is used in agriculture to increase soil fertility and plant
growth. The use of seaweed fertilizer dates back to antiquity and has a
broad array of benefits for soils. Seaweed fertilizer can be applied in a
number of different forms, including refined liquid <a href="https://en.wikipedia.org/wiki/Extract" title="Extract">extracts</a> and dried, pulverized organic material. Through its composition of various bioactive molecules, seaweed functions as a strong <a href="https://en.wikipedia.org/wiki/Soil_conditioner" title="Soil conditioner">soil conditioner</a>, <a href="https://en.wikipedia.org/wiki/Bioremediation" title="Bioremediation">bio-remediator</a>, and <a href="https://en.wikipedia.org/wiki/Biological_pest_control" title="Biological pest control">biological pest control</a>, with each seaweed <a href="https://en.wikipedia.org/wiki/Phylum" title="Phylum">phylum</a> offering various benefits to soil and crop health.
These benefits can include increased tolerance to abiotic stressors,
improved soil texture and water retention, and reduced occurrence of
diseases.
</p><p>On a broader socio-ecological scale, seaweed <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">aquaculture</a> and fertilizer development have significant roles in biogeochemical <a href="https://en.wikipedia.org/wiki/Nutrient_cycle" title="Nutrient cycle">nutrient cycling</a> through carbon storage and the uptake of nitrogen and phosphorus. Seaweed fertilizer application to soils can also alter the structure and function of <a href="https://en.wikipedia.org/wiki/Microorganism" title="Microorganism">microbial</a> communities. Seaweed aquaculture has the potential to yield <a href="https://en.wikipedia.org/wiki/Ecosystem_service" title="Ecosystem service">ecosystem services</a>
by providing a source of nutrition to human communities and a mechanism
for improving water quality in natural systems and aquaculture
operations. The rising popularity of organic farming practices is drawing increased
attention towards the various applications of seaweed-derived
fertilizers and soil additives. While the seaweed fertilizer industry is
still in its infancy, it holds significant potential for sustainable
economic development as well as the reduction of <a href="https://en.wikipedia.org/wiki/Surface_runoff" title="Surface runoff">nutrient runoff</a> in coastal systems.
There are however ongoing challenges associated with the use and
production of seaweed fertilizer including the spread of diseases and <a href="https://en.wikipedia.org/wiki/Invasive_species" title="Invasive species">invasive species</a>, the risk of <a href="https://en.wikipedia.org/wiki/Heavy_metals" title="Heavy metals">heavy-metal</a> accumulation, and the efficiency and refinement of production methods.
</p>
<h2><span class="mw-headline" id="Nomenclature_and_taxonomy">Nomenclature and taxonomy</span></h2></div></div></div><p>“Seaweed" is one of the common names given to multicellular macroalgae, such as green algae (<a href="https://en.wikipedia.org/wiki/Chlorophyta" title="Chlorophyta">Chlorophyta</a>), brown algae (<a href="https://en.wikipedia.org/wiki/Brown_algae" title="Brown algae">Phaeophyceae</a>), and red algae (<a href="https://en.wikipedia.org/wiki/Red_algae" title="Red algae">Rhodophyta</a>). The term, seaweed is sometimes used to refer to <a href="https://en.wikipedia.org/wiki/Microalgae" title="Microalgae">microalgae</a> and plants as well. Seaweeds are typically <a href="https://en.wikipedia.org/wiki/Benthic_zone" title="Benthic zone">benthic</a>
organisms which have a structure called a holdfast, that keeps them
anchored to the sea floor; they also have a stipe, otherwise known as a
stem, and blade-shaped foliage. Sargassum seaweed is one exception to this anatomy and function, as it does not attach to the benthic environment.
The color of seaweeds generally follows depth/light, with green
seaweeds, brown seaweeds, and red seaweeds corresponding to shallow,
moderate, and deeper waters respectively; red seaweeds are sometimes
found up to 30 meters in depth. The smallest seaweeds grow only a few millimeters in height, while the largest seaweeds can grow up to 50 meters in height.
There are an estimated 1,800 green, 1,800 brown, and 6,200 red seaweed
species in existence. Brown seaweeds are generally known as kelp, but
are also known by other common names such as rockweed and wracks.
Red seaweeds are the most diverse group of seaweed, and along with
green seaweeds, are most closely related to terrestrial plants, whereas
brown seaweeds are the most distantly related to terrestrial plants. Seaweeds are found extensively in shallow natural environments, and farmed both in the ocean and in land-based <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">aquaculture</a> operations. Most brown seaweeds that are found in the wild are from the genera <i><a href="https://en.wikipedia.org/wiki/Laminaria" title="Laminaria">Laminaria</a></i>, <i><a href="https://en.wikipedia.org/wiki/Undaria" title="Undaria">Undaria</a></i>, <i><a href="https://en.wikipedia.org/wiki/Hijiki" title="Hijiki">Hizikia</a>,</i> whereas most brown seaweeds that are farmed for uses such as fertilizer and heavy metal indication, are from the species <i><a href="https://en.wikipedia.org/wiki/Ascophyllum" title="Ascophyllum">Ascophyllum</a></i>, <i><a href="https://en.wikipedia.org/wiki/Ecklonia" title="Ecklonia">Ecklonia</a></i>, <i><a href="https://en.wikipedia.org/wiki/Fucus" title="Fucus">Fucus</a></i>, <i><a href="https://en.wikipedia.org/wiki/Sargassum" title="Sargassum">Sargassum</a></i>. Green seaweeds that are used as bioindicators, for heavy metal indication for example, are from the genera <i>Ulva</i> and <i>Enteromorpha</i>. Red seaweed from the genus <i>Poryphora,</i> is commonly used for human food.
</p>
<h2><span class="mw-headline" id="History">History</span></h2><p>The
first written record of agricultural use seaweed was from ancient Greek
and Roman civilizations in the 2nd century, where foraged beach castings
were used to feed livestock and wrap plant roots for preservation. However, <a href="https://en.wikipedia.org/wiki/Isotope_analysis" title="Isotope analysis">stable isotope analysis</a> of prehistoric sheep teeth in the <a href="https://en.wikipedia.org/wiki/Orkney" title="Orkney">Orkneys</a> indicate that early peoples used seaweed as livestock <a href="https://en.wikipedia.org/wiki/Fodder" title="Fodder">fodder</a>
over 5,000 years ago, and researchers speculate that foraged seaweed
was also used as fertilizer because ashed remnants of seaweed were found
in archeological sites.
Such agricultural techniques might have been key to the survival of
early settlements in Scotland. Historical records and archaeological
evidence of seaweed fertilizer use in the coastal <a href="https://en.wikipedia.org/wiki/Atlantic_Ocean" title="Atlantic Ocean">Atlantic</a> are vast and scattered, ranging from <a href="https://en.wikipedia.org/wiki/Scandinavia" title="Scandinavia">Scandinavia</a> to <a href="https://en.wikipedia.org/wiki/Portugal" title="Portugal">Portugal</a>, from the <a href="https://en.wikipedia.org/wiki/Neolithic" title="Neolithic">neolithic</a> period through the 20th century. Most details of seaweed fertilizer use come from the <a href="https://en.wikipedia.org/wiki/British_Isles" title="British Isles">British Isles</a>, <a href="https://en.wikipedia.org/wiki/Channel_Islands" title="Channel Islands">Channel Islands</a>, Normandy and <a href="https://en.wikipedia.org/wiki/Brittany" title="Brittany">Brittany</a>
(France), where a variety of application techniques were used over the
centuries, and some continue to this day. Ireland has a long history
(12th century) of harvesting seaweed for fertilizing nutrient-poor post
glacial soils using composted <a href="https://en.wikipedia.org/wiki/Manure" title="Manure">manure</a> as enrichment and the increased agricultural productivity allowed the Irish population to grow substantially. The Channel Islands (12th century) used a dried blend of red and brown seaweeds, called "Vraic" or "<a href="https://en.wikipedia.org/wiki/Wrack_(seaweed)" title="Wrack (seaweed)">wrack</a>", to spread over potato fields during the winter months to enrich before planting the crop in the spring.
Similarly, coastal people in Normandy and Brittany have been collecting
"wrack" using wood rakes since the neolithic period, though the
fertilizer composition originally included all <a href="https://en.wikipedia.org/wiki/Marine_debris" title="Marine debris">marine debris</a> that washed ashore. In 17th–19th century <a href="https://en.wikipedia.org/wiki/Scotland" title="Scotland">Scotland</a>, <i>Fucus spp</i>. were cultivated by placing rocky substrate in the <a href="https://en.wikipedia.org/wiki/Intertidal_zone" title="Intertidal zone">intertidal</a> zones to encourage seaweed settlement.
The seaweed biomass was then used in composted trenches, where crops
(potatoes, oats, wheat, onions) were grown directly in the sandy
fertilizer mixture. This ‘<a href="https://en.wikipedia.org/wiki/Lazy_bed" title="Lazy bed">lazy bed</a>’
method afforded minimal crop rotation and allowed rugged landscape and
acidic soils to be farmed, where plant growth was otherwise unsuitable. The high value of seaweed in these regions caused political disputes
over harvesting rights and in Ireland such rights were established
before the country itself.
These early applications of seaweed fertilizer were limited to
coastlines, where the macroalgae could be harvested from the intertidal
or collected after a storm washed it to shore. However, dried wrack
mixtures or ashed ‘fucus’ <a href="https://en.wikipedia.org/wiki/Potash" title="Potash">potash</a> could be transported further inland because it weighs less than wet seaweed.
</p><p>Seaweed fertilizer spread inland when a <a href="https://en.wikipedia.org/wiki/Kelp" title="Kelp">kelp</a> industry developed in Scotland, Norway, and Brittany in the 18th and 19th century. The industry developed out of demand for ashed soda, or potash, which
was used to create glass and soap, and led to shortages for agricultural
applications in traditional coastal communities. Potash is a
water-soluble <a href="https://en.wikipedia.org/wiki/Potassium" title="Potassium">potassium</a> rich concentrate made from plant matter, so it was also exported as a fertilizer. Coastal communities in the seaweed industry both expanded and struggled to keep up with the demand.
Early commercial kelp export in Scotland devastated traditional
agriculture in the region because intensive labor was needed during the
seaweed growing season to harvest and process the kelp, which led to a
labor transition from farming to kelp processing. Additionally,
exploitation of kelp resources for potash production left little kelp
behind for local fertilizer and coastal land became more desirable than
inland regions. The Scottish seaweed industry went through multiple boom and bust
cycles, employing 10,000 families and producing 3,000 tonnes of ash per
year during its peak. The export price of kelp ash dropped in 1822, leading to a sudden
emigration from the area because the crop was no longer profitable
enough to support such a large industry. Kelp exploitation and toxic ash
processing caused ecological and economic damage in Orkney and left
many people sick and blinded. The kelp industry picked up again for <a href="https://en.wikipedia.org/wiki/Iodine" title="Iodine">iodine</a> production in 1845, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alginate" title="Alginate">alginate</a> (a thickening agent) production in the early 1900s, which reinvigorated kelp harvest.
</p><p>Global production of seaweed fertilizer largely phased out when <a href="https://en.wikipedia.org/wiki/Fertilizer" title="Fertilizer">chemical fertilizers</a> were developed in the 1920s, due to the cheaper production cost. Chemical fertilizers revolutionized the agriculture industry and
allowed the human population to grow far beyond the limits of
traditional food production methods. Synthetic fertilizers are still the predominant global source for
commercial agricultural applications due to the cheap cost of production
and widespread access. However, small scale organic farmers and coastal
communities continued traditional seaweed techniques in regions with a
rich seaweed history. The first industrial kelp liquid fertilizer, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Maxicrop" title="Maxicrop">Maxicrop</a>, was created by Reginald Milton in 1947.
The creation of liquid fertilizer has allowed for more widespread
application of seaweed-derived fertilizer to inland regions and sparked a
growing <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Agronomic" title="Agronomic">agronomic</a> interest in seaweed for a variety of agricultural applications, including foliage spray, biostimulants, and soil conditioning. Interestingly, the historic rise of seaweed <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">aquaculture</a>
did not align with fertilizer production because the European countries
that produce seaweed fertilizer haven't developed a significant
aquaculture industry; <a href="https://en.wikipedia.org/wiki/Seaweed_farming" title="Seaweed farming">seaweed farming</a> is also currently dominated by China and Indonesia, where the crop is grown for food and other lucrative uses.
</p>
<h2><span class="mw-headline" id="Aquaculture">Aquaculture</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed_Farms_in_South_Korea_(detail)_(17322757055).jpg"><img class="mw-file-element" data-file-height="2623" data-file-width="4302" height="244" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bd/Seaweed_Farms_in_South_Korea_%28detail%29_%2817322757055%29.jpg/220px-Seaweed_Farms_in_South_Korea_%28detail%29_%2817322757055%29.jpg" width="400" /></a><figcaption>A
satellite image of seaweed aquaculture off the southern coast of South
Korea. The dark squares displayed in the image are fields of seaweed
growing.</figcaption></figure>
<p>The development of modern seaweed <a href="https://en.wikipedia.org/wiki/Mariculture" title="Mariculture">mariculture</a>/aquaculture has allowed the expansion of seaweed fertilizer research and improved processing methods since the 1950s. Seaweed has been cultivated in Asian countries for food production for
centuries, but seaweed aquaculture is now growing rapidly across the
world for specialty use in <a href="https://en.wikipedia.org/wiki/Biofuel" title="Biofuel">biofuel</a>, <a href="https://en.wikipedia.org/wiki/Agar" title="Agar">agar</a>, cosmetics, medicine, and <a href="https://en.wikipedia.org/wiki/Bioplastic" title="Bioplastic">bioplastics</a>. The nascent agricultural seaweed sector, including animal feed, soil additives, and <a href="https://en.wikipedia.org/wiki/Agrochemical" title="Agrochemical">agrochemicals</a>, makes up less than 1% of the overall global value of seaweed aquaculture.
However, significant interest in agricultural applications of the crop
has increased dramatically since 1950, as specialty agrochemical uses
for seaweed materials have been demonstrated through scientific
research. Increased concern over the depletion and degradation of marine resources in the past century, coupled with the threats of <a href="https://en.wikipedia.org/wiki/Climate_change" title="Climate change">climate change</a>, has increased global interest in sustainable solutions for <a href="https://en.wikipedia.org/wiki/The_Blue_Economy" title="The Blue Economy">blue economic</a> development of the oceans.
Seaweed aquaculture is promoted as a solution to expand novel industry
development and food security while simultaneously restoring damaged
ecosystems.
Unlike terrestrial crops, growing seaweed requires no land, feed,
fertilizers, pesticides, and water resources. Different seaweeds also
offer a variety of <a href="https://en.wikipedia.org/wiki/Ecosystem_service" title="Ecosystem service">ecosystem services</a> (discussed below), which contribute to the growing popularity of seaweed as a <a href="https://en.wikipedia.org/wiki/Bioremediation" title="Bioremediation">bioremediation</a> crop.
Fertilizer plays and important role in sustainable seaweed aquaculture
development because seaweed farming can help alleviate excess nutrient
loading associated with terrestrial chemical fertilizer run-off and
applying organic seaweed fertilizer on soil closes the nutrient loop
between land and sea.
Additionally, seaweed fertilizer can be produced using by-products from
other industries or raw materials that are unsuitable for human
consumption, such as rotting or infected biomass or biowaste products
from carrageenan processing methods.
Seaweed aquaculture is also important for supporting sustainble growth
of the seaweed fertilizer industry because it limits the potential for
exploitation of native seaweed for commercial interests. However, the nascent seaweed aquaculture industry faces a number of challenges to sustainable development, as discussed below.
Environmental impacts of seaweed harvest and production need to be
carefully scrutinized to protect coastal communities and maintain the
socioeconomic benefits of using seaweed resources in industry.
</p>
<h3><span class="mw-headline" id="Ecosystem_services">Ecosystem services</span></h3><p>Seaweed
mariculture for purposes including fertilizer production, has the
potential to improve environmental conditions in coastal habitats,
especially with regards to toxic algal blooms, as mariculture seaweeds
uptake excess nutrients that have resulted from runoff, thereby
inhibiting the growth of toxic algal blooms that harm local ecosystems.
Seaweed fertilizers can also be more biodegradable, less toxic, and
less hazardous than chemical fertilizers, depending on the type of
seaweed fertilizer. Seaweeds are used in aquaculture operations to uptake fish waste as nutrients and improve water quality parameters.
Humans use seaweeds nutritionally as food, industrially for animal feed
and plant fertilizer, and ecologically to improve environmental
conditions. Seaweeds have been consumed by humans for centuries because they have excellent nutritional profiles, contain minerals, <a href="https://en.wikipedia.org/wiki/Trace_element" title="Trace element">trace elements</a>, <a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acids</a>, and <a href="https://en.wikipedia.org/wiki/Vitamin" title="Vitamin">vitamins</a>, and are high in fiber and low in calories. Red seaweeds have the highest protein content and brown seaweeds have the lowest protein content. Of all the red seaweeds, <i>Porphyra</i>, is the genus most frequently used for human consumption. Brown seaweeds are so plentiful that they most used for industrial animal feeds and fertilizers.
Furthermore, seaweeds are currently being investigated as a potential
source of sustainable biofuel, as well as being investigated as a
potential component of wastewater treatment, because some species are
able to absorb and remove heavy metals and other toxicants from water
bodies, and also generally serve as water quality indicators.
</p>
<h3><span class="mw-headline" id="Ecosystem_impacts">Ecosystem impacts</span></h3><p>Any ecosystem impacts of using seaweed for plant and crop fertilizer are primarily due to how the seaweed is harvested.
Large-scale, unsustainable seaweed farming can lead to the displacement
and alteration of native habitats due to the presence of farming
infrastructure in the water, and day-to-day anthropogenic operations in
the area. Seaweed is currently harvested from farmed sources, wild sources, and from beach collection efforts.
Harvesting wild seaweed will tend to have negative impacts on local
ecosystems, especially if existing populations are overexploited and
rendered unable to provide <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ecosystem_services" title="Ecosystem services">ecosystem services</a>.
There is also a risk that large, industrial scale seaweed monocultures
will be established in natural benthic environments, leading to the
competitive exclusion of native seaweeds and sea grasses, which inhabit
the depths underneath seaweed farms.
Furthermore, large, industrial scale seaweed farming can alter the
natural benthic environment that they are established in, by altering
environmental parameters such as light availability, the movement of
water, sedimentation rates and nutrient levels, and due to the general,
overall stress caused by anthropogenic factors.
</p>
<h2><span class="mw-headline" id="Production_and_application_methods">Production and application methods</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Mineral_Compositions_of_Seaweeds.png"><img class="mw-file-element" data-file-height="784" data-file-width="1434" height="218" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Mineral_Compositions_of_Seaweeds.png/220px-Mineral_Compositions_of_Seaweeds.png" width="400" /></a><figcaption>The composition of various minerals found in three different species of seaweed.</figcaption></figure>
<p>Brown seaweeds are most commonly used for fertilizer production, at present and historically. Seaweed fertilizer can be used as a crude addition to soil as <a href="https://en.wikipedia.org/wiki/Mulch" title="Mulch">mulch</a>,
composted to break down the hardy raw material, or dried and pulverized
to make the nutrients more bioavailable to plant roots. Compost fertilization is a technique that any small-scale organic farm can readily use if they have access to seaweed, though extracts are more common for large-scale commercial applications.
Commercial manufacturing processes are often more technical than
traditional techniques using raw biomass and use different biochemical
processes to concentrate and extract the most beneficial nutrients from
seaweed.
</p><p>A simple liquid fertilizer can be created by <a href="https://en.wikipedia.org/wiki/Fermentation" title="Fermentation">fermenting</a> seaweed leaves in water, though the process is intensified and hastened industrially through heat and pressure. Other methods for liquid extraction include a soft-extraction with low
temperature milling to suspend fine particles in water, heating the raw
material with alkaline sodium or potassium to extract nutrients, and the
addition of enzymes to aid in biochemical decomposition.Extraction of bioavailable nutrients from raw seaweed is achieved by breaking down the hardy <a href="https://en.wikipedia.org/wiki/Cell_wall" title="Cell wall">cell walls</a> through physical techniques, such as <a href="https://en.wikipedia.org/wiki/Ultrasound" title="Ultrasound">ultrasound</a> extraction, boiling, or freeze-thaw. Biological fermentation techniques are also used to degrade the cells. Physical extraction techniques are often faster, but more expensive and result in poorer crop yield in trials. Since seaweed extract has <a href="https://en.wikipedia.org/wiki/Chelation" title="Chelation">chelating</a> properties that maintain trace metal ions bioavailability to plants, additional <a href="https://en.wikipedia.org/wiki/Micronutrient" title="Micronutrient">micronutrients</a> are often added to solution to increase the fertilization benefit to specific crops.
Organic fertilization techniques have lower environmental consequences
in comparison to the production of artificial chemical fertilizers,
because they use no harsh caustic or organic <a href="https://en.wikipedia.org/wiki/Solvent" title="Solvent">solvents</a>
to produce fertilizer and the seaweed raw material is a renewable
resource, as opposed to mineral deposits and fossil fuels needed to
synthesize chemical fertilizer.
Large-scale agricultural use of synthetic fertilizer depletes soil
fertility and increases water hardness over time, so recent trends in
agricultural development are following an organic approach to sustain
food production through improved soil management and bio-fertilization
techniques.
Seaweed extracts are bio-fertilizers that can also be used as
biostimulants, which are applied to enhance nutrient efficiency and
abiotic stress tolerance.
New extraction technologies are being developed to improve efficiency
and target the isolation of specific compounds for specialized
applications of seaweed biostimulants, though specific extraction
techniques are frequently trade secrets. Additionally, many liquid fertilizer extraction processes can complement other industrial uses for seaweed, such as <a href="https://en.wikipedia.org/wiki/Carrageenan" title="Carrageenan">carrageenan</a> production, which increases the economic benefit of the same seaweed crop.
</p>
<h2><span class="mw-headline" id="Nutrient_cycling">Nutrient cycling</span></h2><p>To
support a growing seaweed aquaculture industry many studies have
evaluated the nutrient cycle dynamics of different seaweed species in
addition to exploring co-production applications including
bioremediation and carbon sequestration. Seaweeds can form highly productive communities in coastal regions, dominating the nutrient cycles within these ecosystems.
As primary producers, seaweeds incorporate inorganic carbon, light, and
nutrients (such as nitrogen and phosphorus), into biomass through
photosynthesis.
Harvesting seaweed from marine environments results in the net removal
of these elements from these ecosystems in addition to the removal of
heavy metals and contaminants.
</p><p>For photosynthesis, seaweeds utilize both inorganic nitrogen, in the forms of <a href="https://en.wikipedia.org/wiki/Nitrate" title="Nitrate">nitrate</a> (NO<sub>3</sub><sup>−</sup>) and <a href="https://en.wikipedia.org/wiki/Ammonium" title="Ammonium">ammonium</a> (NH<sub>4</sub><sup>+</sup>), and organic nitrogen in the form of <a href="https://en.wikipedia.org/wiki/Urea" title="Urea">urea</a>. Primary production using nitrate is generally considered <a href="https://en.wikipedia.org/wiki/New_production" title="New production">new production</a> because nitrate is externally supplied through <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a>
and riverine input, and often has been converted from forms of nitrogen
that are released from biological respiration. However, primary
production using ammonium is denoted as recycled production because
ammonium is internally supplied through regeneration by <a href="https://en.wikipedia.org/wiki/Heterotroph" title="Heterotroph">heterotrophs</a> within ecosystems.
For example, the ammonium excreted by fish and invertebrates within the
same coastal ecosystems as seaweeds can support seaweed production
through providing a nitrogen source. Phosphorus is supplied inorganically as <a href="https://en.wikipedia.org/wiki/Phosphate" title="Phosphate">phosphate</a> (PO<sub>4</sub><sup>3-</sup>) and generally follows similar seasonal patterns to nitrate. Additionally, seaweeds require inorganic carbon, typically supplied from the environment in the form of carbon dioxide (CO<sub>2</sub>) or <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate</a> (HCO<sub>3</sub><sup>−</sup>).
</p><p>Similar to other marine photosynthesizing organisms like <a href="https://en.wikipedia.org/wiki/Phytoplankton" title="Phytoplankton">phytoplankton</a>, seaweeds also experience nutrient limitations impacting their ability to grow. Nitrogen is the most commonly found limiting nutrient for seaweed
photosynthesis, although phosphorus has also been found to be limiting. The ratio of inorganic carbon, nitrogen, and phosphorus is also important to ensure balanced growth.
Generally the N:P ratio for seaweeds is 30:1, however, the ratio can
differ significantly among species and requires experimental testing to
identify the specific ratio for a given species.
Exploring the relationship between nutrient cycling and seaweed growth
is vital to optimizing seaweed aquaculture and understanding the
functions and benefits of seaweed applications, including its use as a
fertilizer, bio-remediator, and in the blue economy.
</p>
<h3><span class="mw-headline" id="Coastal_eutrophication">Coastal eutrophication</span></h3><p>A
growing population and intensification of industry and agriculture have
increased the volume of wastewater discharged into coastal marine
ecosystems.
These waters typically contain high concentrations of nitrogen and
phosphorus, and relatively high heavy metal concentrations, leading to <a href="https://en.wikipedia.org/wiki/Eutrophication" title="Eutrophication">eutrophication</a> of many coastal ecosystems.
Eutrophication results from the excessive nutrient load within these
ecosystems resulting from the pollution of waters entering the oceans
from industry, animal feed, and synthetic fertilizers, and thus
over-fertilizes these systems. Eutrophication leads to high productivity in coastal systems, which can result in coastal <a href="https://en.wikipedia.org/wiki/Hypoxia_(environmental)" title="Hypoxia (environmental)">hypoxia</a> and <a href="https://en.wikipedia.org/wiki/Ocean_acidification" title="Ocean acidification">ocean acidification</a>, two major concerns for coastal ecosystems. A notable service of seaweed farming is its ability to act as a
bio-remediator through uptake and removal of excessive nutrients in
coastal ecosystems with their application to land uses.
Brown algae, due in part to their large size, have been noted for their
high productivity and corresponding high nutrient uptake in coastal
ecosystems.
Additionally, studies have focused on how brown algae growth can be
optimized to increase biomass production and therefore increase the
quantity of nutrients removed from these ecosystems. Studies have also explored the potential of brown algae to sequester large volumes of carbon (<a href="https://en.wikipedia.org/wiki/Blue_carbon" title="Blue carbon">blue carbon</a>).
</p>
<h3><span class="mw-headline" id="Bio-remediation_in_eutrophic_ecosystems">Bio-remediation in eutrophic ecosystems</span></h3><p>Seaweeds
have received significant attention for their potential to mitigate
eutrophication in coastal ecosystems through nutrient uptake during
primary production in <a href="https://en.wikipedia.org/wiki/Integrated_multi-trophic_aquaculture" title="Integrated multi-trophic aquaculture">integrated multi-trophic aquaculture</a> (IMTA).
Bioremediation involves the use of biological organisms to lower the
concentrations of nitrogen, phosphorus, and heavy metal concentrations
in marine ecosystems.
The bioremediation potential of seaweeds depends, in part, on their
growth rate which is controlled by numerous factors including water
movement, light, <a href="https://en.wikipedia.org/wiki/Desiccation" title="Desiccation">desiccation</a>, temperature, salinity, life stage, and age class.
It has also been proposed that in eutrophic ecosystems phosphorus can
become limiting to seaweed growth due to the high N:P ratio of the
wastewater entering these ecosystems.
Bioremediation practices have been widely used due to their
cost-effective ability to reduce excess nutrients in coastal ecosystems
leading to a decrease in <a href="https://en.wikipedia.org/wiki/Harmful_algal_bloom" title="Harmful algal bloom">harmful algal blooms</a> and an oxygenation of the water column. Seaweeds have also been studied for their potential use in the <a href="https://en.wikipedia.org/wiki/Biosorption" title="Biosorption">biosorption</a> and accumulation of heavy metals in polluted waters, although the accumulation of heavy metals may impact algal growth.
</p>
<h3><span class="mw-headline" id="Blue_carbon">Blue carbon</span></h3><p>
Blue carbon methods involve the use of marine ecosystems for carbon
storage and burial. Seaweed aquaculture shows potential to act as a CO<sub>2</sub>
sink through the uptake of carbon during photosynthesis, transformation
of inorganic carbon into biomass, and ultimately the fixation of carbon
which can later be exported and buried. Duarte et al. (2017) outline a potential strategy for a seaweed farming blue carbon initiative.
However the contribution of seaweed to blue carbon has faced
controversy over the ability of seaweed to act as a net sink for
atmospheric carbon.
Krause-Jensen et al., (2018) discuss two main criteria for seaweed
farming to be considered a blue carbon initiative: it must be both
extensive in size and sequestration rate and possess the ability to be
actionable by humans, that the sequestration rate can be managed by
human action.
Seaweed farming, including the use of seaweed as fertilizer could
become an important contributor in climate mitigation strategies through
carbon sequestration and storage.</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed_Fertilizer_Benefits.jpg"><img class="mw-file-element" data-file-height="927" data-file-width="761" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/Seaweed_Fertilizer_Benefits.jpg/220px-Seaweed_Fertilizer_Benefits.jpg" width="328" /></a><figcaption>The positive impacts conferred by seaweed fertilizer on crops.</figcaption></figure>
<h2><span class="mw-headline" id="Functions_and_benefits_of_seaweed_fertilizer">Functions and benefits of seaweed fertilizer</span></h2><h3><span class="mw-headline" id="Fertilization">Fertilization</span></h3><p>Seaweed functions as an organic bio-fertilizer. Because seaweed is rich in micro and <a href="https://en.wikipedia.org/wiki/Nutrient" title="Nutrient">macronutrients</a>, <a href="https://en.wikipedia.org/wiki/Humic_substance" title="Humic substance">humic acids</a>, and <a href="https://en.wikipedia.org/wiki/Plant_hormone" title="Plant hormone">phytohormones</a>, it enhances <a href="https://en.wikipedia.org/wiki/Soil_fertility" title="Soil fertility">soil fertility</a>. In addition, seaweed-derived fertilizers contain <a href="https://en.wikipedia.org/wiki/Polysaccharide" title="Polysaccharide">polysaccharides</a>, <a href="https://en.wikipedia.org/wiki/Protein" title="Protein">proteins</a>, and <a href="https://en.wikipedia.org/wiki/Fatty_acid" title="Fatty acid">fatty acids</a> which improve the moisture and nutrient retention of soil, contributing to improved crop growth. More trace minerals are found in seaweed than those produced with animal byproducts.
</p><p>The application of seaweed fertilizers can also result in
enhanced tolerance to abiotic stressors that generally inhibit crop
growth and yield such as low moisture, high salinity, and freezing
temperatures.
These stress tolerance benefits appear to be driven by physiological
changes induced in crops by the seaweed, including improved energy
storage, enhanced root morphology, and greater metabolic potential,
enhancing the plant's ability to survive unfavorable conditions. <i><a href="https://en.wikipedia.org/wiki/Kappaphycus_alvarezii" title="Kappaphycus alvarezii">Kappaphycus alvarezzi</a></i> extracts have also resulted in considerable reductions in the leakage of <a href="https://en.wikipedia.org/wiki/Electrolyte" title="Electrolyte">electrolytes</a>, as well as enhanced <a href="https://en.wikipedia.org/wiki/Chlorophyll" title="Chlorophyll">chlorophyll</a> and <a href="https://en.wikipedia.org/wiki/Carotenoid" title="Carotenoid">carotenoid</a> production, and water content. Research has also demonstrated that wheat plants treated with seaweed extracts have accumulated key <a href="https://en.wikipedia.org/wiki/Osmoprotectant" title="Osmoprotectant">osmoprotectants</a> such as <a href="https://en.wikipedia.org/wiki/Proline" title="Proline">proline</a>, other amino acids, and total protein.
</p><p><a href="https://en.wikipedia.org/wiki/Leaf" title="Leaf">Foliar</a>
applications of seaweed fertilizer extract have been shown to improve
the uptake of nitrogen, phosphorus, potassium, and sulfur in soybeans
such as G<i>lycine max</i>.
Research has also demonstrated that brown algae seaweed extracts can
improve tomato plant growth, overall crop yield, and resistance to
environmental stressors. Additional documented benefits of using seaweed as a fertilizer include reduced <a href="https://en.wikipedia.org/wiki/Transplanting" title="Transplanting">transplant shock</a>, increased leaf surface area, and increased sugar content.
</p>
<h3><span class="mw-headline" id="Soil_conditioning">Soil conditioning</span></h3><p>As a soil conditioner, seaweed fertilizer can improve the physical qualities of soil, such as aeration and water retention. Clay soils that lack organic matter and <a href="https://en.wikipedia.org/wiki/Porosity" title="Porosity">porosity</a> benefit from the <a href="https://en.wikipedia.org/wiki/Humic_substance" title="Humic substance">humic acid</a> and soluble <a href="https://en.wikipedia.org/wiki/Alginic_acid" title="Alginic acid">alginates</a> found in seaweed. These compounds bond with metallic radicals which cause the <a href="https://en.wikipedia.org/wiki/Clay" title="Clay">clay</a> particles to aggregate, thereby improving the texture, aeration, and retention of the soil by stimulating clay disaggregation. The degradation of alginates also supplements the soil with organic matter, enhancing its fertility. In particular, brown seaweeds such as <i>Sargassum</i> are known
to have valuable soil conditioning properties. This seaweed contains
soluble alginates as well as alginic acid, which catalyzes the bacterial
decomposition of organic matter. This process improves <a href="https://en.wikipedia.org/wiki/Soil_quality" title="Soil quality">soil quality</a> by enhancing populations of <a href="https://en.wikipedia.org/wiki/Nitrogen_fixation" title="Nitrogen fixation">nitrogen-fixing</a> bacteria and by supplementing the soil with additional conditioners through the waste products produced by these bacteria.
</p>
<h3><span class="mw-headline" id="Bio-remediation_of_polluted_soils">Bio-remediation of polluted soils</span></h3><p>Seaweed functions as a bio-remediator through its <a href="https://en.wikipedia.org/wiki/Adsorption" title="Adsorption">adsorption</a> of harmful pollutants. <a href="https://en.wikipedia.org/wiki/Functional_group" title="Functional group">Functional groups</a> on the algal surface such as <a href="https://en.wikipedia.org/wiki/Ester" title="Ester">ester</a>, hydroxyl, carbonyl amino, sulfhydryl, and phosphate groups drive the biosorption of heavy metal ions. Seaweeds such as <i>Gracilaria corticata varcartecala</i> and <i>Grateloupia lithophila</i> effectively remove a wide variety of heavy metals, including <a href="https://en.wikipedia.org/wiki/Chromium" title="Chromium">chromium</a> (III) and (IV), <a href="https://en.wikipedia.org/wiki/Mercury_(element)" title="Mercury (element)">mercury</a> (II), lead (II), and cadmium (II) from their environment. In addition, <i>Ulva spp.</i> and <i>Gelidium spp.</i> have been shown to enhance the degradation of <a href="https://en.wikipedia.org/wiki/DDT" title="DDT">DDT</a> in polluted soils and may reduce its bioavailability.
Although there is significant potential for seaweed to serve as a
bio-remediator for polluted soils, more research is needed to fully
develop the mechanisms for this process in the context of agriculture.
Heavy metals accumulated by seaweed fertilizer may transfer to crops in
some cases, causing significant implications for public health.
</p><p>The application of <a href="https://en.wikipedia.org/wiki/Biochar" title="Biochar">biochar</a>
is another strategy that can remediate and enhance infertile soils.
Seaweed can be transformed into biochar and used as a means of
increasing the organic matter and nutrient content of the soil.
Different types of seaweed appear to yield unique nutrients and
parameters; red seaweeds, for example, create biochar that is rich in
potassium and sulfur and is more acidic than biochar generated from
brown seaweeds.
While this is a new field of research, current data shows that targeted
breeding of seaweeds may result in biochars that can be tailored to
different types of soil and crops.
</p>
<h3><span class="mw-headline" id="Integrated_pest_management">Integrated pest management</span></h3><p>The addition of seaweed to soil can increase crop health and resistance to diseases. Seaweeds contain a diverse array of bioactive molecules that can respond to diseases and pests, including <a href="https://en.wikipedia.org/wiki/Steroid" title="Steroid">steroids</a>, <a href="https://en.wikipedia.org/wiki/Terpene" title="Terpene">terpenes</a>, <a href="https://en.wikipedia.org/wiki/Acetogenin" title="Acetogenin">acetogenins</a>, and amino acid-derived <a href="https://en.wikipedia.org/wiki/Polymer" title="Polymer">polymers</a>. The application of seaweed extracts reduces the presence of harmful pests including <a href="https://en.wikipedia.org/wiki/Nematode" title="Nematode">nematodes</a> and insects. While the application of seaweed seems to reduce the harmful effects of
nematode infestation, the combination of seaweed application and <a href="https://en.wikipedia.org/wiki/Carbofuran" title="Carbofuran">carbofuran</a>, a chemical <a href="https://en.wikipedia.org/wiki/Nematicide" title="Nematicide">nematocide</a>, seems to be most effective.
In addition, several species of seaweed appear to hinder the early
growth and development of numerous detrimental insects, including <i>Sargassum swartzii</i>, <i><a href="https://en.wikipedia.org/wiki/Padina_pavonica" title="Padina pavonica">Padina pavonica</a></i>, and <i>Caulerpa denticulata</i>.
</p>
<h2><span class="mw-headline" id="Soil_microbial_response_to_seaweed_fertilizer_treatment">Soil microbial response to seaweed fertilizer treatment</span></h2><p>Shifts in bacterial and fungal communities, in response to seaweed fertilizer treatment, have only recently been studied. Soil <a href="https://en.wikipedia.org/wiki/Microbial_consortium" title="Microbial consortium">Microbial community</a> composition and functionality is largely driven by underlying soil health and abiotic properties. Many DNA sequencing and <a href="https://en.wikipedia.org/wiki/Omics" title="Omics">omics</a>-based approaches, combined with <a href="https://en.wikipedia.org/wiki/Greenhouse" title="Greenhouse">greenhouse</a> experiments, have been used to characterize microbial responses to seaweed fertilizer treatment on a wide variety of crops. Deep <a href="https://en.wikipedia.org/wiki/16S_ribosomal_RNA" title="16S ribosomal RNA">16S ribosomal RNA</a> (rRNA) <a href="https://en.wikipedia.org/wiki/Amplicon" title="Amplicon">amplicon</a> sequencing of the bacteria found in the soils of tomato plots, treated with a <i>Sargassum horneri</i> fermented seaweed fertilizer, showed a large shift in <a href="https://en.wikipedia.org/wiki/Alpha_diversity" title="Alpha diversity">alpha diversity</a> and <a href="https://en.wikipedia.org/wiki/Beta_diversity" title="Beta diversity">beta diversity</a> indices between untreated soils and soils after 60 days. This shift in community composition was correlated with a 1.48-1.83 times increase in tomato yield in treated soils. Though dominant bacterial phyla remained similar between treatment groups, changes in the abundance of the class, <a href="https://en.wikipedia.org/wiki/Bacilli" title="Bacilli">Bacilli</a> and family, <i><a href="https://en.wikipedia.org/wiki/Micrococcaceae" title="Micrococcaceae">Micrococcaceae</a></i> were noted. Enzyme assays also displayed an increase in <a href="https://en.wikipedia.org/wiki/Protease" title="Protease">protease</a>, <a href="https://en.wikipedia.org/wiki/Polyphenol_oxidase" title="Polyphenol oxidase">polyphenol oxidase</a>, <a href="https://en.wikipedia.org/wiki/Dehydrogenase" title="Dehydrogenase">dehydrogenase</a>, <a href="https://en.wikipedia.org/wiki/Invertase" title="Invertase">invertase</a>, and <a href="https://en.wikipedia.org/wiki/Urease" title="Urease">urease</a> activity, which was thought to be induced by microbial community alterations.
Each of the microbial and enzymatic results listed above were noted to
improve the nutrient turnover and quality in soils treated with
fertilizer. To investigate interactions between plant growth-promoting <a href="https://en.wikipedia.org/wiki/Rhizobacteria" title="Rhizobacteria">rhizobacteria</a> (PGPR) and seaweed-derived extract, Ngoroyemoto et al. treated <i><a href="https://en.wikipedia.org/wiki/Amaranthus_hybridus" title="Amaranthus hybridus">Amaranthus hybridus</a></i> with both Kelpak and PGPR and measured impacts on plant growth. It was found that the treatment of plants with Kelpak® and the bacteria, <i><a href="https://en.wikipedia.org/wiki/Pseudomonas_fluorescens" title="Pseudomonas fluorescens">Pseudomonas fluorescens</a></i> and <i><a href="https://en.wikipedia.org/wiki/Bacillus_licheniformis" title="Bacillus licheniformis">Bacillus licheniformis</a></i>, decreased plant stress responses and increased production.
The most recently mentioned study provides implications for crop
benefits when the application of seaweed fertilizer to soils favors the
growth of PGPR.
</p><p>Wang et al. found that apple <a href="https://en.wikipedia.org/wiki/Seedling" title="Seedling">seedlings</a>
treated with seaweed fertilizer differed markedly in fungal diversity
and species richness, when compared to no-treatment control groups.
These findings were complemented by increases in soil quality and
enzyme activities in treated soil groups, which supports the hypothesis
that the fertilizer promoted the growth of plant-beneficial fungal
species. With the use of 16S rRNA and fungal <a href="https://en.wikipedia.org/wiki/Internal_transcribed_spacer" title="Internal transcribed spacer">internal transcribed spacer</a> (ITS) sequencing, Renaut et al. examined the effect of <i>Ascophyllum nodosum</i> extract treatment on the <a href="https://en.wikipedia.org/wiki/Rhizosphere" title="Rhizosphere">rhizospheres</a> of pepper and tomato plants in greenhouses. This group found that bacterial and fungal <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Species_composition" title="Species composition">species composition</a> and community structures differed based on treatment. A rise of the abundance of certain <a href="https://en.wikipedia.org/wiki/Amplicon_sequence_variant" title="Amplicon sequence variant">amplicon sequence variants</a> (ASVs) were also directly correlated with increases in plant health and growth. These ASVs included fungi in the family, <i>Microascaceae</i>, the genus, <i><a href="https://en.wikipedia.org/wiki/Mortierella" title="Mortierella">Mortierella</a> spp.</i>, and several other uncultured ASVs. A large diversity of bacterial ASVs were identified to be positively correlated with growth in this same study, including <i><a href="https://en.wikipedia.org/wiki/Rhizobium" title="Rhizobium">Rhizobium</a></i>, <i><a href="https://en.wikipedia.org/wiki/Sphingomonas" title="Sphingomonas">Sphingomonas</a></i>, <i><a href="https://en.wikipedia.org/wiki/Sphingobium" title="Sphingobium">Sphingobium</a></i>, and <i><a href="https://en.wikipedia.org/wiki/Bradyrhizobium" title="Bradyrhizobium">Bradyrhizobium</a></i>.
</p>
<h3><span class="mw-headline" id="Resistance_to_plant_pathogens">Resistance to plant pathogens</span></h3><p>The
application of seaweed fertilizer may also increase resistance to plant
pathogens. In greenhouse samples, Ali et al. tested the treatment of <i>Ascophyllum nodosum</i>
extract on tomato and sweet pepper crops and found that it both
increased plant health and reduced the incidence of plant pathogens. Further investigation showed that the up-regulation of pathogen defense-related enzymes led to the reduction of the pathogens, <i><a href="https://en.wikipedia.org/wiki/Xanthomonas_campestris_pv._vesicatoria" title="Xanthomonas campestris pv. vesicatoria">Xanthomonas campestris pv. vesicatoria</a></i> and <i><a href="https://en.wikipedia.org/wiki/Alternaria_solani" title="Alternaria solani">Alternaria solani</a></i>. Chen et al. found that <i>Ascophyllum nodosum</i> treatment positively impacted the community composition of maize rhizospheres.
This may have critical implications for plant health because the
structure of rhizosphere microbial communities can aid in the resistance
of plants to soil-borne pathogens.
</p><p>Other pathogen reductions include the mitigation of carrot foliar fungal diseases following <i>Ascophyllum nodosum</i> treatment and inoculation with the fungal pathogens, <i><a href="https://en.wikipedia.org/wiki/Alternaria_radicina" title="Alternaria radicina">Alternaria radicina</a></i> and <i><a href="https://en.wikipedia.org/wiki/Botrytis_cinerea" title="Botrytis cinerea">Botrytis cinerea</a></i>.
Reduced disease severity was noted at 10 and 20 days post-inoculation
in comparison to control plants, and the seaweed treatment was found to
be more effective at reducing disease pathology than <a href="https://en.wikipedia.org/wiki/Salicylic_acid" title="Salicylic acid">salicylic acid</a>, a known plant protector from biotic and abiotic stresses. Islam et al. had similar results when treating <i><a href="https://en.wikipedia.org/wiki/Arabidopsis_thaliana" title="Arabidopsis thaliana">Arabidopsis thaliana</a></i> with brown algal extracts, followed by inoculation with the fungal pathogen <i><a href="https://en.wikipedia.org/wiki/Phytophthora_cinnamomi" title="Phytophthora cinnamomi">Phytophthora cinnamomi</a></i>. This group analyzed plant <a href="https://en.wikipedia.org/wiki/Transcription_(biology)" title="Transcription (biology)">RNA transcripts</a> and found that the seaweed extract primed <i>A. thaliana</i>
to defend against the fungal pathogen before its inoculation, which led
to increased host survival and decreased susceptibility to infection.
</p><p>Fewer studies have analyzed the impact of seaweed fertilizer treatment on plant resistance to <a href="https://en.wikipedia.org/wiki/Viral_pathogenesis" title="Viral pathogenesis">viral pathogens</a>, however limited auspicious results have been demonstrated.
It has been shown that green, brown, and red seaweeds contain
polysaccharides that illicit pathogen response pathways in plants, which
primes defense against viruses, along with bacteria and fungi. Specifically, defense enzymes, including <a href="https://en.wikipedia.org/wiki/Phenylalanine_ammonia-lyase" title="Phenylalanine ammonia-lyase">phenylalanine ammonia lyase</a> and <a href="https://en.wikipedia.org/wiki/Lipoxygenase" title="Lipoxygenase">lipoxygenase</a>, are activated and lead to viral defense. Aqueous and ethanolic extracts from the brown alga, <i><a href="https://en.wikipedia.org/wiki/Durvillaea_antarctica" title="Durvillaea antarctica">Durvillaea antarctica</a></i> was shown to decrease pathological symptoms of <a href="https://en.wikipedia.org/wiki/Tobacco_mosaic_virus" title="Tobacco mosaic virus">tobacco mosaic virus</a> (TMV) in tobacco leaves. Another study done on tobacco plants found that sulfated fucan <a href="https://en.wikipedia.org/wiki/Oligosaccharide" title="Oligosaccharide">oligosaccharides</a>, extracted from brown algae, induced local and <a href="https://en.wikipedia.org/wiki/Systemic_acquired_resistance" title="Systemic acquired resistance">systemic acquired resistance</a> to TMV.
Based on the above results, it can be stated that the application of
seaweed fertilizers has considerable potential to provide broad benefits
to agricultural crops and resistance to bacterial, fungal, and viral
plant pathogens.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-51168550118999778052024-03-17T18:24:00.002-04:002024-03-17T18:24:44.346-04:00Seaweed<div class="vector-column-end">
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<div class="hatnote navigation-not-searchable" role="note"><a href="https://en.wikipedia.org/wiki/Seaweed">https://en.wikipedia.org/wiki/Seaweed</a><br /></div><div class="hatnote navigation-not-searchable" role="note"><br /></div>
<table class="infobox biota biota-infobox">
<tbody><tr>
<th class="section-header" colspan="2" style="background: rgb(245,215,255);">Seaweed<div style="font-size: smaller; font-weight: normal;">Informal group of macroscopic marine algae</div>
</th></tr>
<tr>
<td class="image-section" colspan="2"><span class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Fucus_serratus_2015-09-08_ag_M0010140.jpg"><img alt=""Fucus serratus"" class="mw-file-element" data-file-height="2736" data-file-width="3648" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Fucus_serratus_2015-09-08_ag_M0010140.jpg/220px-Fucus_serratus_2015-09-08_ag_M0010140.jpg" width="400" /></a></span>
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<td class="image-section" colspan="2"><i><a href="https://en.wikipedia.org/wiki/Fucus_serratus" title="Fucus serratus">Fucus serratus</a></i>
</td></tr>
<tr>
<th class="section-header" colspan="2" style="background: rgb(245,215,255); min-width: 15em; text-align: center;"><a href="https://en.wikipedia.org/wiki/Taxonomy_(biology)" title="Taxonomy (biology)">Scientific classification</a><span class="plainlinks" style="float: right; font-size: smaller; margin-left: -3em; padding-right: 0.4em;"><span><a href="https://en.wikipedia.org/wiki/Template:Taxonomy/Eukaryota" title="Edit this classification"><img alt="Edit this classification" class="mw-file-element" data-file-height="20" data-file-width="20" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/OOjs_UI_icon_edit-ltr.svg/15px-OOjs_UI_icon_edit-ltr.svg.png" width="15" /></a></span></span>
</th></tr>
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<td>Domain:
</td>
<td><a href="https://en.wikipedia.org/wiki/Eukaryote" title="Eukaryote">Eukaryota</a>
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<th class="section-header" colspan="2" style="background: rgb(245,215,255);">Seaweeds can be found in the following groups
</th></tr>
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<td class="section-content" colspan="2">
<ul><li><a href="https://en.wikipedia.org/wiki/Chlorophyta" title="Chlorophyta">Chlorophyta</a> (green algae)</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Phaeophyceae" title="Phaeophyceae">Phaeophyceae</a> (brown algae)</li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Phaeothamniophyceae" title="Phaeothamniophyceae">Phaeothamniophyceae</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chrysophyceae" title="Chrysophyceae">Chrysophyceae</a> (gold algae)</li><li><a href="https://en.wikipedia.org/wiki/Cyanobacteria" title="Cyanobacteria">Cyanobacteria</a></li><li><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rhodophyta" title="Rhodophyta">Rhodophyta</a> (red algae)</li></ul>
</td></tr></tbody></table>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Ascophyllum_nodosum.jpg"><img alt="Photo of seaweed with small swollen areas at the end of each frond" class="mw-file-element" data-file-height="1000" data-file-width="635" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Ascophyllum_nodosum.jpg/170px-Ascophyllum_nodosum.jpg" width="254" /></a><figcaption><i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ascophyllum_nodosum" title="Ascophyllum nodosum">Ascophyllum nodosum</a></i> exposed to the sun in <a href="https://en.wikipedia.org/wiki/Nova_Scotia" title="Nova Scotia">Nova Scotia</a>, <a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a></figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Codiumfragile.jpg"><img alt="Photo of detached seaweed frond lying on sand" class="mw-file-element" data-file-height="1704" data-file-width="2272" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Codiumfragile.jpg/220px-Codiumfragile.jpg" width="400" /></a><figcaption>Dead man's fingers (<i><a href="https://en.wikipedia.org/wiki/Codium_fragile" title="Codium fragile">Codium fragile</a></i>) off the <a href="https://en.wikipedia.org/wiki/Massachusetts" title="Massachusetts">Massachusetts</a> coast in the United States</figcaption></figure>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Kelp_forest_Otago_1s.JPG"><img alt="Photo of seaweed with the tip floating at the surface" class="mw-file-element" data-file-height="972" data-file-width="1296" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Kelp_forest_Otago_1s.JPG/220px-Kelp_forest_Otago_1s.JPG" width="400" /></a><figcaption>The top of a <a href="https://en.wikipedia.org/wiki/Kelp_forest" title="Kelp forest">kelp forest</a> in <a href="https://en.wikipedia.org/wiki/Otago" title="Otago">Otago</a>, New Zealand</figcaption></figure>
<p><b>Seaweed</b>, or <b>macroalgae</b>, refers to thousands of species of <a href="https://en.wikipedia.org/wiki/Macroscopic_scale" title="Macroscopic scale">macroscopic</a>, <a href="https://en.wikipedia.org/wiki/Multicellular_organism" title="Multicellular organism">multicellular</a>, <a href="https://en.wikipedia.org/wiki/Ocean" title="Ocean">marine</a> <a href="https://en.wikipedia.org/wiki/Algae" title="Algae">algae</a>. The term includes some types of <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Rhodophyta" title="Rhodophyta">Rhodophyta</a></i> (red), <i><a href="https://en.wikipedia.org/wiki/Brown_algae" title="Brown algae">Phaeophyta</a></i> (brown) and <i><a href="https://en.wikipedia.org/wiki/Chlorophyta" title="Chlorophyta">Chlorophyta</a></i> (green) macroalgae. Seaweed species such as <a href="https://en.wikipedia.org/wiki/Kelp" title="Kelp">kelps</a> provide essential nursery habitat for fisheries and other marine species and thus protect food sources; other species, such as <a href="https://en.wikipedia.org/wiki/Plankton" title="Plankton">planktonic</a> algae, play a vital role in <a href="https://en.wikipedia.org/wiki/Blue_carbon" title="Blue carbon">capturing carbon</a> and producing at least 50% of Earth's oxygen.
</p><p>Natural seaweed ecosystems are sometimes under threat from human activity. For example, mechanical <a href="https://en.wikipedia.org/wiki/Dredging" title="Dredging">dredging</a> of kelp destroys the resource and dependent fisheries. Other forces also threaten some seaweed ecosystems; for example, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Wasting_disease" title="Wasting disease">wasting disease</a> in predators of <a href="https://en.wikipedia.org/wiki/Strongylocentrotus_purpuratus" title="Strongylocentrotus purpuratus">purple urchins</a> has led to an urchin population surge which has destroyed large <a href="https://en.wikipedia.org/wiki/Kelp_forest" title="Kelp forest">kelp forest</a> regions off the coast of California.
</p><p>Humans have a long history of cultivating seaweeds for their uses. In recent years, <a href="https://en.wikipedia.org/wiki/Seaweed_farming" title="Seaweed farming">seaweed farming</a> has become a global agricultural practice, providing food, source material for various chemical uses (such as <a href="https://en.wikipedia.org/wiki/Carrageenan" title="Carrageenan">carrageenan</a>),
cattle feeds and fertilizers. Due to their importance in marine
ecologies and for absorbing carbon dioxide, recent attention has been on
cultivating seaweeds as a potential <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">climate change mitigation</a> strategy for <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Biosequestration" title="Biosequestration">biosequestration of carbon dioxide</a>, alongside other benefits like <a href="https://en.wikipedia.org/wiki/Nutrient_pollution" title="Nutrient pollution">nutrient pollution</a> reduction, increased habitat for coastal aquatic species, and reducing local <a href="https://en.wikipedia.org/wiki/Ocean_acidification" title="Ocean acidification">ocean acidification</a>. The <a href="https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Climate_Change" title="Intergovernmental Panel on Climate Change">IPCC</a> <a href="https://en.wikipedia.org/wiki/Special_Report_on_the_Ocean_and_Cryosphere_in_a_Changing_Climate" title="Special Report on the Ocean and Cryosphere in a Changing Climate">Special Report on the Ocean and Cryosphere in a Changing Climate</a> recommends "further research attention" as a mitigation tactic.
</p>
<h2><span class="mw-headline" id="Taxonomy">Taxonomy</span></h2></div></div></div><p>"Seaweed"
lacks a formal definition, but seaweed generally lives in the ocean and
is visible to the naked eye. The term refers to both flowering plants
submerged in the ocean, like <a href="https://en.wikipedia.org/wiki/Zostera" title="Zostera">eelgrass</a>, as well as larger marine algae. Generally, it is one of several groups of multicellular <a href="https://en.wikipedia.org/wiki/Algae" title="Algae">algae</a>; <a href="https://en.wikipedia.org/wiki/Red_algae" title="Red algae">red</a>, <a href="https://en.wikipedia.org/wiki/Green_algae" title="Green algae">green</a> and <a href="https://en.wikipedia.org/wiki/Brown_algae" title="Brown algae">brown</a>. They lack one common multicellular ancestor, forming a <a href="https://en.wikipedia.org/wiki/Polyphyly" title="Polyphyly">polyphyletic</a> group. In addition, blue-green algae (<a href="https://en.wikipedia.org/wiki/Cyanobacteria" title="Cyanobacteria">Cyanobacteria</a>) are occasionally considered in seaweed literature.
</p><p>The number of seaweed species is still a topic of discussed among
scientists, but it is most likely that there are several thousand
species of seaweed.
</p>
<h3><span class="mw-headline" id="Genera">Genera</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Claudea_elegans_tetrasporangia.jpg"><img class="mw-file-element" data-file-height="1980" data-file-width="3000" height="264" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Claudea_elegans_tetrasporangia.jpg/220px-Claudea_elegans_tetrasporangia.jpg" width="400" /></a><figcaption><i>Claudea elegans tetrasporangia</i></figcaption></figure>
<p>The following table lists a very few example genera of seaweed.
</p>
<table class="wikitable">
<tbody><tr>
<th>Genus</th>
<th><br /></th>
<th>Algae<br />Phylum</th>
<th>Remarks
</th></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Caulerpa" title="Caulerpa">Caulerpa</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Caulerpa_prolifera.JPG"><img class="mw-file-element" data-file-height="2806" data-file-width="2518" height="111" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/62/Caulerpa_prolifera.JPG/100px-Caulerpa_prolifera.JPG" width="100" /></a></span></td>
<td>Green</td>
<td>Submerged.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Fucus" title="Fucus">Fucus</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Fucus_serratus2.jpg"><img class="mw-file-element" data-file-height="600" data-file-width="800" height="113" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/89/Fucus_serratus2.jpg/150px-Fucus_serratus2.jpg" width="150" /></a></span></td>
<td>Brown</td>
<td>In intertidal zones on rocky shores.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Gracilaria" title="Gracilaria">Gracilaria</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Gracilaria2.JPG"><img class="mw-file-element" data-file-height="1704" data-file-width="2272" height="113" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Gracilaria2.JPG/150px-Gracilaria2.JPG" width="150" /></a></span></td>
<td>Red</td>
<td>Cultivated for food.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Laminaria" title="Laminaria">Laminaria</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Laminaria_hyperborea_-_K%C3%B6hler%E2%80%93s_Medizinal-Pflanzen-214.jpg"><img class="mw-file-element" data-file-height="597" data-file-width="491" height="122" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Laminaria_hyperborea_-_K%C3%B6hler%E2%80%93s_Medizinal-Pflanzen-214.jpg/100px-Laminaria_hyperborea_-_K%C3%B6hler%E2%80%93s_Medizinal-Pflanzen-214.jpg" width="100" /></a></span></td>
<td>Brown</td>
<td>Also known as kelp<br />8–30 m under water and<br />cultivated for food.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Macrocystis" title="Macrocystis">Macrocystis</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Giantkelp2_300.jpg"><img class="mw-file-element" data-file-height="839" data-file-width="1271" height="99" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Giantkelp2_300.jpg/150px-Giantkelp2_300.jpg" width="150" /></a></span></td>
<td>Brown</td>
<td>Giant kelp<br />forming floating canopies.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Monostroma" title="Monostroma">Monostroma</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed-farmer.JPG"><img class="mw-file-element" data-file-height="960" data-file-width="1280" height="113" src="https://upload.wikimedia.org/wikipedia/en/thumb/b/b3/Seaweed-farmer.JPG/150px-Seaweed-farmer.JPG" width="150" /></a></span></td>
<td>Green</td>
<td>
<br /></td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Porphyra" title="Porphyra">Porphyra</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Pyropia_yezoensis.jpg"><img class="mw-file-element" data-file-height="600" data-file-width="800" height="113" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Pyropia_yezoensis.jpg/150px-Pyropia_yezoensis.jpg" width="150" /></a></span></td>
<td>Red</td>
<td>Intertidal zones in temperate climate and<br />cultivated for food.
</td></tr>
<tr>
<td><i><a href="https://en.wikipedia.org/wiki/Sargassum" title="Sargassum">Sargassum</a></i></td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Sargassum_weeds_closeup.jpg"><img class="mw-file-element" data-file-height="450" data-file-width="600" height="113" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/63/Sargassum_weeds_closeup.jpg/150px-Sargassum_weeds_closeup.jpg" width="150" /></a></span></td>
<td>Brown</td>
<td>Pelagic especially in the Sargasso Sea.
</td></tr></tbody></table>
<h2><span class="mw-headline" id="Anatomy">Anatomy</span></h2><p>Seaweed's appearance resembles non-<a href="https://en.wikipedia.org/wiki/Wood" title="Wood">woody</a> terrestrial <a href="https://en.wikipedia.org/wiki/Plant" title="Plant">plants</a>. Its anatomy includes:
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/Thallus" title="Thallus">Thallus</a>: algal body
<ul><li><a href="https://en.wikipedia.org/wiki/Lamina_(algae)" title="Lamina (algae)">Lamina</a> or blade: flattened structure that is somewhat leaf-like
<ul><li><a href="https://en.wikipedia.org/wiki/Sorus" title="Sorus">Sorus</a>: <a href="https://en.wikipedia.org/wiki/Spore" title="Spore">spore</a> cluster</li><li><i><a href="https://en.wikipedia.org/wiki/Pneumatocyst" title="Pneumatocyst">pneumatocyst</a></i>, air bladder: a flotation-assisting organ on the blade</li><li><a href="https://en.wikipedia.org/wiki/Kelp" title="Kelp">Kelp</a>, float: a flotation-assisting organ between the lamina and stipe</li></ul></li><li><a href="https://en.wikipedia.org/wiki/Stipe_(botany)" title="Stipe (botany)">Stipe</a>: stem-like structure, may be absent</li><li><a href="https://en.wikipedia.org/wiki/Holdfast_(biology)" title="Holdfast (biology)">Holdfast</a>: basal structure providing attachment to a substrate
<ul><li><a href="https://en.wikipedia.org/wiki/Holdfast_(biology)" title="Holdfast (biology)">Haptera</a>: finger-like extension of the holdfast that anchors to a <a href="https://en.wikipedia.org/wiki/Benthic_zone" title="Benthic zone">benthic</a> substrate</li></ul></li></ul></li></ul>
<p>The stipe and blade are collectively known as the <a href="https://en.wikipedia.org/wiki/Frond" title="Frond">frond</a>.
</p>
<h2><span class="mw-headline" id="Ecology">Ecology</span></h2><figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:NSW_seabed_2.JPG"><img class="mw-file-element" data-file-height="3000" data-file-width="4000" height="165" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/NSW_seabed_2.JPG/220px-NSW_seabed_2.JPG" width="220" /></a><figcaption>Seaweed covers this rocky seabed on the east coast of Australia</figcaption></figure>
<p>Two environmental requirements dominate seaweed <a href="https://en.wikipedia.org/wiki/Ecology" title="Ecology">ecology</a>. These are seawater (or at least <a href="https://en.wikipedia.org/wiki/Brackish_water" title="Brackish water">brackish water</a>) and light sufficient to support <a href="https://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a>. Another common requirement is an attachment point, and therefore seaweed most commonly inhabits the <a href="https://en.wikipedia.org/wiki/Littoral_zone" title="Littoral zone">littoral zone</a> (nearshore waters) and within that zone, on rocky shores more than on sand or shingle. In addition, there are few <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genera" title="Genera">genera</a> (e.g., <i><a href="https://en.wikipedia.org/wiki/Sargassum" title="Sargassum">Sargassum</a></i> and <i><a href="https://en.wikipedia.org/wiki/Gracilaria" title="Gracilaria">Gracilaria</a></i>) which do not live attached to the sea floor, but float freely.
</p><p>Seaweed occupies various ecological niches. At the surface, they
are only wetted by the tops of sea spray, while some species may attach
to a substrate several meters deep. In some areas, littoral seaweed
colonies can extend miles out to sea. The deepest living seaweed are some species of <a href="https://en.wikipedia.org/wiki/Red_algae" title="Red algae">red algae</a>. Others have adapted to live in <a href="https://en.wikipedia.org/wiki/Tide_pool" title="Tide pool">tidal rock pools</a>. In this habitat, seaweed must withstand rapidly changing temperature and <a href="https://en.wikipedia.org/wiki/Salinity" title="Salinity">salinity</a> and occasional drying.
</p><p>Macroalgae and macroalgal detritus have also been shown to be an
important food source for benthic organisms, because macroalgae shed old
<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fronds" title="Fronds">fronds</a>.
These macroalgal fronds tend to be utilized by <a href="https://en.wikipedia.org/wiki/Benthos" title="Benthos">benthos</a> in the <a href="https://en.wikipedia.org/wiki/Intertidal_zone" title="Intertidal zone">intertidal zone</a> close to the shore.
Alternatively, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pneumatocysts" title="Pneumatocysts">pneumatocysts</a> (gas filled "bubbles") can keep the macroalgae <a href="https://en.wikipedia.org/wiki/Thallus" title="Thallus">thallus</a> afloat; fronds are transported by wind and currents from the coast into the deep ocean. It has been shown that <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Benthic_organisms" title="Benthic organisms">benthic organisms</a> also at several 100 m tend to utilize these macroalgae remnants.
</p><p>As macroalgae takes up <a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a> and releases <a href="https://en.wikipedia.org/wiki/Oxygen" title="Oxygen">oxygen</a> in the <a href="https://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a>, macroalgae fronds can also contribute to <a href="https://en.wikipedia.org/wiki/Carbon_sequestration" title="Carbon sequestration">carbon sequestration</a> in the ocean, when the macroalgal fronds drift offshore into the deep <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_basins" title="Ocean basins">ocean basins</a> and sink to the sea floor without being remineralized by organisms. The importance of this process for the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Blue_Carbon" title="Blue Carbon">Blue Carbon</a> storage is currently a topic of discussion among scientists.
</p>
<h3><span class="mw-headline" id="Biogeographic_expansion">Biogeographic expansion</span></h3><p>Nowadays
a number of vectors - e.g., transport on ship hulls, exchanges among
shellfish farmers, global warming, opening of trans-oceanic canals -
all combine to enhance the transfer of exotic seaweeds to new
environments. Since the piercing of the Suez Canal, the situation is
particularly acute in the Mediterranean Sea, a 'marine biodiversity
hotspot' that now registers over 120 newly introduced seaweed species
-the largest number in the world.
</p>
<h2><span class="mw-headline" id="Production">Production</span></h2><p>As of 2019, 35,818,961 tonnes were produced, of which 97.38% were produced in Asian countries.
</p>
<table border="1" style="text-align: right;">
<caption>Seaweed production
</caption>
<tbody><tr>
<th>Country
</th>
<th>tonns<br /> per year,<br />cultured and wild
</th></tr>
<tr>
<td>China
</td>
<td>20,351,442
</td></tr>
<tr>
<td>Indonesia
</td>
<td>9,962,900
</td></tr>
<tr>
<td>South Korea
</td>
<td>1,821,475
</td></tr>
<tr>
<td>Philippines
</td>
<td>1,500,326
</td></tr>
<tr>
<td>North Korea
</td>
<td>603,000
</td></tr>
<tr>
<td>Chile
</td>
<td>427,508
</td></tr>
<tr>
<td>Japan
</td>
<td>412,300
</td></tr>
<tr>
<td>Malaysia
</td>
<td>188,110
</td></tr>
<tr>
<td>Norway
</td>
<td>163,197
</td></tr>
<tr>
<td>United Republic of Tanzania
</td>
<td>106,069
</td></tr></tbody></table>
<h3><span class="mw-headline" id="Farming">Farming</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<p><a href="https://en.wikipedia.org/wiki/Seaweed_farming" title="Seaweed farming">Seaweed farming</a> or <a href="https://en.wikipedia.org/wiki/Kelp" title="Kelp">kelp</a> farming is the practice of <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">cultivating</a> and <a href="https://en.wikipedia.org/wiki/Harvest" title="Harvest">harvesting</a> seaweed. In its simplest form farmers gather from natural beds, while at the other extreme farmers fully control the crop's <a href="https://en.wikipedia.org/wiki/Biological_life_cycle" title="Biological life cycle">life cycle</a>.
</p><p>The seven most cultivated <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Taxa" title="Taxa">taxa</a> are <i><a href="https://en.wikipedia.org/wiki/Eucheuma" title="Eucheuma">Eucheuma</a></i> spp., <i><a href="https://en.wikipedia.org/wiki/Kappaphycus_alvarezii" title="Kappaphycus alvarezii">Kappaphycus alvarezii</a></i>, <i><a href="https://en.wikipedia.org/wiki/Gracilaria" title="Gracilaria">Gracilaria</a></i> spp., <i><a href="https://en.wikipedia.org/wiki/Saccharina_japonica" title="Saccharina japonica">Saccharina japonica</a></i>, <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Undaria_pinnatifida" title="Undaria pinnatifida">Undaria pinnatifida</a></i>, <i><a href="https://en.wikipedia.org/wiki/Pyropia" title="Pyropia">Pyropia</a></i> spp., and <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sargassum_fusiforme" title="Sargassum fusiforme">Sargassum fusiforme</a></i>. <i>Eucheuma</i> and <i>K. alvarezii</i> are attractive for <a href="https://en.wikipedia.org/wiki/Carrageenan" title="Carrageenan">carrageenan</a> (a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gelling_agent" title="Gelling agent">gelling agent</a>); <i>Gracilaria</i> is farmed for <a href="https://en.wikipedia.org/wiki/Agar" title="Agar">agar</a>; the rest are eaten after limited processing. Seaweeds are different from <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mangroves" title="Mangroves">mangroves</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seagrasses" title="Seagrasses">seagrasses</a>, as they are photosynthetic algal organisms and are non-flowering.
</p><p>The largest seaweed-producing countries as of 2022 are <a href="https://en.wikipedia.org/wiki/China" title="China">China</a> (58.62%) and <a href="https://en.wikipedia.org/wiki/Indonesia" title="Indonesia">Indonesia</a> (28.6%); followed by <a href="https://en.wikipedia.org/wiki/South_Korea" title="South Korea">South Korea</a> (5.09%) and the <a href="https://en.wikipedia.org/wiki/Philippines" title="Philippines">Philippines</a> (4.19%). Other notable producers include <a href="https://en.wikipedia.org/wiki/North_Korea" title="North Korea">North Korea</a> (1.6%), <a href="https://en.wikipedia.org/wiki/Japan" title="Japan">Japan</a> (1.15%), <a href="https://en.wikipedia.org/wiki/Malaysia" title="Malaysia">Malaysia</a> (0.53%), <a href="https://en.wikipedia.org/wiki/Zanzibar" title="Zanzibar">Zanzibar</a> (<a href="https://en.wikipedia.org/wiki/Tanzania" title="Tanzania">Tanzania</a>, 0.5%), and <a href="https://en.wikipedia.org/wiki/Chile" title="Chile">Chile</a> (0.3%). Seaweed farming has frequently been developed to improve economic conditions and to reduce fishing pressure.
</p><p>The <a href="https://en.wikipedia.org/wiki/Food_and_Agriculture_Organization" title="Food and Agriculture Organization">Food and Agriculture Organization</a>
(FAO), reported that world production in 2019 was over 35 million
tonnes. North America produced some 23,000 tonnes of wet seaweed.
Alaska, Maine, France, and Norway each more than doubled their seaweed
production since 2018<i>.</i> As of 2019, seaweed represented 30% of marine <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">aquaculture</a>.
</p>
Seaweed farming is a <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_removal" title="Carbon dioxide removal">carbon negative</a> crop, with a high potential for <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">climate change mitigation</a>.<sup> </sup>The IPCC <a href="https://en.wikipedia.org/wiki/Special_Report_on_the_Ocean_and_Cryosphere_in_a_Changing_Climate" title="Special Report on the Ocean and Cryosphere in a Changing Climate">Special Report on the Ocean and Cryosphere in a Changing Climate</a> recommends "further research attention" as a mitigation tactic. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/World_Wildlife_Fund" title="World Wildlife Fund">World Wildlife Fund</a>, Oceans 2050, and <a href="https://en.wikipedia.org/wiki/The_Nature_Conservancy" title="The Nature Conservancy">The Nature Conservancy</a> publicly support expanded seaweed cultivation.</div></div>
<h2><span class="mw-headline" id="Uses">Uses</span></h2><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Seaweed_farming#Uses" title="Seaweed farming">Seaweed farming § Uses</a></div>
<p>Seaweed has a variety of uses, for which it is <a href="https://en.wikipedia.org/wiki/Seaweed_farming" title="Seaweed farming">farmed</a> or foraged.
</p>
<h3><span class="mw-headline" id="Food">Food</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Edible_seaweed" title="Edible seaweed">Edible seaweed</a></div>
<p>Seaweed is consumed across the world, particularly in <a href="https://en.wikipedia.org/wiki/East_Asia" title="East Asia">East Asia</a>, e.g., <a href="https://en.wikipedia.org/wiki/Japan" title="Japan">Japan</a>, <a href="https://en.wikipedia.org/wiki/China" title="China">China</a>, <a href="https://en.wikipedia.org/wiki/Korea" title="Korea">Korea</a>, <a href="https://en.wikipedia.org/wiki/Taiwan" title="Taiwan">Taiwan</a> and <a href="https://en.wikipedia.org/wiki/Southeast_Asia" title="Southeast Asia">Southeast Asia</a>, e.g. <a href="https://en.wikipedia.org/wiki/Brunei" title="Brunei">Brunei</a>, <a href="https://en.wikipedia.org/wiki/Singapore" title="Singapore">Singapore</a>, <a href="https://en.wikipedia.org/wiki/Thailand" title="Thailand">Thailand</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Burma" title="Burma">Burma</a>, <a href="https://en.wikipedia.org/wiki/Cambodia" title="Cambodia">Cambodia</a>, <a href="https://en.wikipedia.org/wiki/Vietnam" title="Vietnam">Vietnam</a>, <a href="https://en.wikipedia.org/wiki/Indonesia" title="Indonesia">Indonesia</a>, the <a href="https://en.wikipedia.org/wiki/Philippines" title="Philippines">Philippines</a>, and <a href="https://en.wikipedia.org/wiki/Malaysia" title="Malaysia">Malaysia</a>, as well as in <a href="https://en.wikipedia.org/wiki/South_Africa" title="South Africa">South Africa</a>, <a href="https://en.wikipedia.org/wiki/Belize" title="Belize">Belize</a>, <a href="https://en.wikipedia.org/wiki/Peru" title="Peru">Peru</a>, <a href="https://en.wikipedia.org/wiki/Chile" title="Chile">Chile</a>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Canadian_Maritimes" title="Canadian Maritimes">Canadian Maritimes</a>, <a href="https://en.wikipedia.org/wiki/Scandinavia" title="Scandinavia">Scandinavia</a>, <a href="https://en.wikipedia.org/wiki/South_West_England" title="South West England">South West England</a>, <a href="https://en.wikipedia.org/wiki/Ireland" title="Ireland">Ireland</a>, <a href="https://en.wikipedia.org/wiki/Wales" title="Wales">Wales</a>, <a href="https://en.wikipedia.org/wiki/Limu_(algae)" title="Limu (algae)">Hawaii</a> and <a href="https://en.wikipedia.org/wiki/California" title="California">California</a>, and <a href="https://en.wikipedia.org/wiki/Scotland" title="Scotland">Scotland</a>.
</p><p><a href="https://en.wikipedia.org/wiki/Gim_(food)" title="Gim (food)">Gim</a> (김, Korea), <a href="https://en.wikipedia.org/wiki/Nori" title="Nori">nori</a> (海苔, Japan) and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Zicai" title="Zicai">zicai</a> (紫菜, China) are sheets of dried <i><a href="https://en.wikipedia.org/wiki/Porphyra" title="Porphyra">Porphyra</a></i> used in soups, <a href="https://en.wikipedia.org/wiki/Sushi" title="Sushi">sushi</a> or <i><a href="https://en.wikipedia.org/wiki/Onigiri" title="Onigiri">onigiri</a></i> (rice balls). <i><a href="https://en.wikipedia.org/wiki/Gamet" title="Gamet">Gamet</a></i> in the Philippines, from dried <i><a href="https://en.wikipedia.org/wiki/Pyropia" title="Pyropia">Pyropia</a></i>, is also used as a flavoring ingredient for soups, salads and <a href="https://en.wikipedia.org/wiki/Omelette" title="Omelette">omelettes</a>. <i><a href="https://en.wikipedia.org/wiki/Chondrus_crispus" title="Chondrus crispus">Chondrus crispus</a></i> ('Irish moss' or <a href="https://en.wikipedia.org/wiki/Carrageenan" title="Carrageenan">carrageenan</a> moss) is used in food additives, along with <i><a href="https://en.wikipedia.org/wiki/Kappaphycus" title="Kappaphycus">Kappaphycus</a></i> and <a href="https://en.wikipedia.org/wiki/Gigartinales" title="Gigartinales">G<i>igartinoid</i></a> seaweed. <i>Porphyra</i> is used in <a href="https://en.wikipedia.org/wiki/Wales" title="Wales">Wales</a> to make <a href="https://en.wikipedia.org/wiki/Laverbread" title="Laverbread">laverbread</a> (sometimes with <a href="https://en.wikipedia.org/wiki/Oat" title="Oat">oat</a> flour). In northern <a href="https://en.wikipedia.org/wiki/Belize" title="Belize">Belize</a>, seaweed is mixed with <a href="https://en.wikipedia.org/wiki/Milk" title="Milk">milk</a>, <a href="https://en.wikipedia.org/wiki/Nutmeg" title="Nutmeg">nutmeg</a>, <a href="https://en.wikipedia.org/wiki/Cinnamon" title="Cinnamon">cinnamon</a> and <a href="https://en.wikipedia.org/wiki/Vanilla" title="Vanilla">vanilla</a> to make "<span title="Spanish-language text"><i lang="es">dulce</i></span>" ("sweet").
</p><p><a href="https://en.wikipedia.org/wiki/Alginic_acid" title="Alginic acid">Alginate</a>, <a href="https://en.wikipedia.org/wiki/Agar" title="Agar">agar</a> and <a href="https://en.wikipedia.org/wiki/Carrageenan" title="Carrageenan">carrageenan</a> are gelatinous seaweed products collectively known as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydrocolloid" title="Hydrocolloid">hydrocolloids</a> or <a href="https://en.wikipedia.org/wiki/Phycocolloid" title="Phycocolloid">phycocolloids</a>. Hydrocolloids are food additives.
The food industry exploits their gelling, water-retention, emulsifying
and other physical properties. Agar is used in foods such as
confectionery, meat and poultry products, desserts and beverages and
moulded foods. Carrageenan is used in salad dressings and sauces,
dietetic foods, and as a preservative in meat and fish, dairy items and
baked goods.
</p><p>Seaweeds are used as animal feeds. They have long been grazed by
sheep, horses and cattle in Northern Europe, even though their
nutritional benefits are questionable. Their protein content is low and
their heavy metal content is high, especially for arsenic and iodine,
which are respectively toxic and nutritious.
</p><p>They are valued for fish production. Adding seaweed to livestock feed can substantially reduce <a href="https://en.wikipedia.org/wiki/Methane_emissions" title="Methane emissions">methane emissions</a> from cattle, but only from their feedlot emissions. As of 2021, feedlot emissions account for 11% of overall emissions from cattle.
</p>
<h3><span class="mw-headline" id="Medicine_and_herbs">Medicine and herbs</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Fucoidan" title="Fucoidan">Fucoidan</a></div>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed_600.jpg"><img alt="Photo of rocks covered by dried plant matter" class="mw-file-element" data-file-height="450" data-file-width="600" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Seaweed_600.jpg/220px-Seaweed_600.jpg" width="400" /></a><figcaption>Seaweed-covered rocks in the <a href="https://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a></figcaption></figure>
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed_on_rocks_at_Atlantic_Ocean.jpg"><img alt="Photo of a rock jetty covered with seaweed" class="mw-file-element" data-file-height="2736" data-file-width="3648" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/41/Seaweed_on_rocks_at_Atlantic_Ocean.jpg/220px-Seaweed_on_rocks_at_Atlantic_Ocean.jpg" width="400" /></a><figcaption>Seaweed on rocks on <a href="https://en.wikipedia.org/wiki/Long_Island" title="Long Island">Long Island</a></figcaption></figure>
<p>Alginates are used in wound dressings (see <a href="https://en.wikipedia.org/wiki/Alginate_dressing" title="Alginate dressing">alginate dressing</a>), and dental moulds. In <a href="https://en.wikipedia.org/wiki/Microbiology" title="Microbiology">microbiology</a>, <a href="https://en.wikipedia.org/wiki/Agar" title="Agar">agar</a> is used as a culture medium. Carrageenans, alginates and agaroses, with other macroalgal polysaccharides, have <a href="https://en.wikipedia.org/wiki/Biomedicine" title="Biomedicine">biomedicine</a> applications. <i>Delisea pulchra</i> may interfere with bacterial colonization. Sulfated saccharides from red and green algae inhibit some <a href="https://en.wikipedia.org/wiki/DNA" title="DNA">DNA</a> and <a href="https://en.wikipedia.org/wiki/RNA" title="RNA">RNA</a>-enveloped <a href="https://en.wikipedia.org/wiki/Virus" title="Virus">viruses</a>.
</p><p>Seaweed extract is used in some diet pills. Other seaweed pills exploit the same effect as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gastric_banding" title="Gastric banding">gastric banding</a>, expanding in the stomach to make the stomach feel more full.
</p>
<h3><span class="mw-headline" id="Climate_change_mitigation">Climate change mitigation</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Carbon_sequestration" title="Carbon sequestration">Carbon sequestration</a> and <a href="https://en.wikipedia.org/wiki/Blue_carbon" title="Blue carbon">blue carbon</a></div>
<div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"><br /></div><div class="excerpt">
Seaweed cultivation in the open ocean can act as a form of carbon sequestration to mitigate climate change. Studies have reported that nearshore seaweed forests constitute a source of <a href="https://en.wikipedia.org/wiki/Blue_carbon" title="Blue carbon">blue carbon</a>, as seaweed detritus is carried into the middle and deep ocean thereby sequestering carbon. <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Macrocystis_pyrifera" title="Macrocystis pyrifera">Macrocystis pyrifera</a></i>
(also known as giant kelp) sequesters carbon faster than any other
species. It can reach 60 m in length and grow as rapidly as 50 cm a day. According to one study, covering 9% of the world’s oceans with kelp forests could produce “sufficient <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Biomethane" title="Biomethane">biomethane</a>
to replace all of today’s needs in fossil fuel energy, while removing
53 billion tons of CO2 per year from the atmosphere, restoring
pre-industrial levels”.</div></div>
<h3><span class="mw-headline" id="Other_uses">Other uses</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seaweed_fertilizer" title="Seaweed fertilizer">Seaweed fertilizer</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seaweed_fuel" title="Seaweed fuel">Seaweed fuel</a></div>
<p>Other seaweed may be used as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seaweed_fertilizer" title="Seaweed fertilizer">fertilizer</a>, <a href="https://en.wikipedia.org/wiki/Compost" title="Compost">compost</a> for landscaping, or to combat <a href="https://en.wikipedia.org/wiki/Coastal_erosion" title="Coastal erosion">beach erosion</a> through burial in beach dunes.
</p><p>Seaweed is under consideration as a potential source of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bioethanol" title="Bioethanol">bioethanol</a>.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Harvesting_(cleaning)_algae_that_have_grown_in_an_algae_scrubber.jpg"><img class="mw-file-element" data-file-height="215" data-file-width="288" height="298" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/05/Harvesting_%28cleaning%29_algae_that_have_grown_in_an_algae_scrubber.jpg/220px-Harvesting_%28cleaning%29_algae_that_have_grown_in_an_algae_scrubber.jpg" width="400" /></a><figcaption>Seaweed is lifted out of the top of an algae scrubber/cultivator, to be discarded or used as food, fertilizer, or skin care</figcaption></figure>
<p>Alginates are used in industrial products such as paper coatings,
adhesives, dyes, gels, explosives and in processes such as paper sizing,
textile printing, hydro-mulching and drilling. Seaweed is an ingredient
in toothpaste, cosmetics and paints. Seaweed is used for the production
of bio yarn (a textile).
</p><p>Several of these resources can be obtained from seaweed through <a href="https://en.wikipedia.org/wiki/Biorefinery" title="Biorefinery">biorefining</a>.
</p>
<p><a href="https://en.wikipedia.org/wiki/Seaweed_collecting" title="Seaweed collecting">Seaweed collecting</a>
is the process of collecting, drying and pressing seaweed. It was a
popular pastime in the Victorian era and remains a hobby today. In some
emerging countries, seaweed is harvested daily to support communities.</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Harvesting_seaweed_in_Jambiani.jpg"><img class="mw-file-element" data-file-height="3560" data-file-width="5457" height="262" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Harvesting_seaweed_in_Jambiani.jpg/220px-Harvesting_seaweed_in_Jambiani.jpg" width="400" /></a><figcaption>Women
in Tanzania grow "Mwani" (seaweed in Swahili). The farms are made up of
little sticks in neat rows in the warm, shallow water. Once they
harvest the seaweed, it is used for many purposes: food, cosmetics,
fabric, etc.</figcaption></figure>
<p>Seaweed is sometimes used to build roofs on houses on <a href="https://en.wikipedia.org/wiki/L%C3%A6s%C3%B8" title="Læsø">Læsø</a> in <a href="https://en.wikipedia.org/wiki/Denmark" title="Denmark">Denmark</a>
</p>
<ul class="gallery mw-gallery-traditional"><li class="gallerybox">
<div class="thumb"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Onigiri_at_an_onigiri_restaurant_by_zezebono_in_Tokyo.jpg" title="Onigiri and wakame miso soup, Japan"><img alt="Onigiri and wakame miso soup, Japan" class="mw-file-element" data-file-height="800" data-file-width="600" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Onigiri_at_an_onigiri_restaurant_by_zezebono_in_Tokyo.jpg/150px-Onigiri_at_an_onigiri_restaurant_by_zezebono_in_Tokyo.jpg" width="300" /></a></span></div>
<div class="gallerytext"><i><a href="https://en.wikipedia.org/wiki/Onigiri" title="Onigiri">Onigiri</a></i> and <i><a href="https://en.wikipedia.org/wiki/Wakame" title="Wakame">wakame</a></i> <i><a href="https://en.wikipedia.org/wiki/Miso_soup" title="Miso soup">miso soup</a></i>, Japan</div><div class="gallerytext"> </div>
</li><li class="gallerybox">
<div class="thumb"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Laver_and_toast.JPG" title="Laverbread and toast"><img alt="Laverbread and toast" class="mw-file-element" data-file-height="2099" data-file-width="2299" height="366" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Laver_and_toast.JPG/200px-Laver_and_toast.JPG" width="400" /></a></span></div>
<div class="gallerytext"><a href="https://en.wikipedia.org/wiki/Laverbread" title="Laverbread">Laverbread</a> and toast</div><div class="gallerytext"> </div>
</li><li class="gallerybox">
<div class="thumb"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Seaweed_Farms_in_Indonesia.jpg" title="Small plots being used to farm seaweed in Indonesia, with each rectangle belonging to a different family"><img alt="Photo of near-shore ocean, divided into rectangles, most containing a yards-long, narrow boat" class="mw-file-element" data-file-height="2368" data-file-width="3496" height="270" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Seaweed_Farms_in_Indonesia.jpg/200px-Seaweed_Farms_in_Indonesia.jpg" width="400" /></a></span></div>
<div class="gallerytext">Small plots being used to farm seaweed in <a href="https://en.wikipedia.org/wiki/Indonesia" title="Indonesia">Indonesia</a>, with each rectangle belonging to a different family</div>
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<h2><span class="mw-headline" id="Health_risks">Health risks</span></h2><p>Rotting seaweed is a potent source of <a href="https://en.wikipedia.org/wiki/Hydrogen_sulfide" title="Hydrogen sulfide">hydrogen sulfide</a>, a highly toxic gas, and has been implicated in some incidents of apparent hydrogen-sulphide poisoning. It can cause vomiting and diarrhea.
</p><p>The so-called "stinging seaweed" <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Microcoleus_lyngbyaceus" title="Microcoleus lyngbyaceus">Microcoleus lyngbyaceus</a></i> is a filamentous <a href="https://en.wikipedia.org/wiki/Cyanobacteria" title="Cyanobacteria">cyanobacteria</a> which contains toxins including <a href="https://en.wikipedia.org/wiki/Lyngbyatoxin-a" title="Lyngbyatoxin-a">lyngbyatoxin-a</a> and <a href="https://en.wikipedia.org/wiki/Debromoaplysiatoxin" title="Debromoaplysiatoxin">debromoaplysiatoxin</a>. Direct skin contact can cause <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seaweed_dermatitis" title="Seaweed dermatitis">seaweed dermatitis</a> characterized by painful, burning lesions that last for days.
</p>
<h2><span class="mw-headline" id="Threats">Threats</span></h2><p>Bacterial disease <a href="https://en.wikipedia.org/wiki/Ice-ice" title="Ice-ice">ice-ice</a> infects <i>Kappaphycus</i> (red seaweed), turning its branches white. The disease caused heavy crop losses in the Philippines, Tanzania and Mozambique.
</p><p>Sea <a href="https://en.wikipedia.org/wiki/Urchin_barren" title="Urchin barren">urchin barrens</a>
have replaced kelp forests in multiple areas. They are "almost immune
to starvation". Lifespans can exceed 50 years. When stressed by hunger,
their jaws and teeth enlarge, and they form "fronts" and hunt for food
collectively</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-20450253495275767642024-03-17T16:53:00.003-04:002024-03-17T16:53:20.585-04:00Special Report on the Ocean and Cryosphere in a Changing Climate<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Special_Report_on_the_Ocean_and_Cryosphere_in_a_Changing_Climate">https://en.wikipedia.org/wiki/Special_Report_on_the_Ocean_and_Cryosphere_in_a_Changing_Climate</a></div><div class="noprint" id="siteSub"> <br /></div>
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<div><a href="https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Climate_Change" title="Intergovernmental Panel on Climate Change">Intergovernmental Panel on<br />Climate Change</a><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Intergovernmental_Panel_on_Climate_Change_Logo.svg"><img class="mw-file-element" data-file-height="280" data-file-width="512" height="219" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/10/Intergovernmental_Panel_on_Climate_Change_Logo.svg/250px-Intergovernmental_Panel_on_Climate_Change_Logo.svg.png" width="400" /></a></span>
<div class="sidebar-list mw-collapsible mw-collapsed mw-made-collapsible"></div><br /></div></div></div></div><table class="sidebar sidebar-collapse nomobile nowraplinks"><tbody><tr><td class="sidebar-content"><div class="sidebar-list mw-collapsible mw-collapsed mw-made-collapsible"><div class="sidebar-list-title">IPCC Assessment Reports</div></div></td>
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<div class="sidebar-list mw-collapsible mw-collapsed mw-made-collapsible"></div><br /></td></tr></tbody></table><table class="sidebar sidebar-collapse nomobile nowraplinks"><tbody><tr><td class="sidebar-content"><div class="sidebar-list mw-collapsible mw-collapsed mw-made-collapsible"><div class="sidebar-list-title">IPCC Special Reports</div></div></td>
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<ul><li><a href="https://en.wikipedia.org/wiki/United_Nations_Framework_Convention_on_Climate_Change" title="United Nations Framework Convention on Climate Change">UNFCCC</a></li><li><a href="https://en.wikipedia.org/wiki/World_Meteorological_Organization" title="World Meteorological Organization">WMO</a></li><li><a href="https://en.wikipedia.org/wiki/United_Nations_Environment_Programme" title="United Nations Environment Programme">UNEP</a></li></ul></td></tr></tbody></table>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:IPCC_Special_Report_on_the_Ocean_and_Cryosphere_LR.jpg"><img class="mw-file-element" data-file-height="163" data-file-width="611" height="107" src="https://upload.wikimedia.org/wikipedia/en/thumb/3/33/IPCC_Special_Report_on_the_Ocean_and_Cryosphere_LR.jpg/220px-IPCC_Special_Report_on_the_Ocean_and_Cryosphere_LR.jpg" width="400" /></a><figcaption>Cover of IPCC SROCC</figcaption></figure>
<p>The <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a>' <a href="https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Climate_Change" title="Intergovernmental Panel on Climate Change">Intergovernmental Panel on Climate Change</a>'s (IPCC) <b>Special Report on the Ocean and Cryosphere in a Changing Climate</b> (SROCC) is a report about the <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change" title="Effects of climate change">effects of climate change</a> on the <a href="https://en.wikipedia.org/wiki/Ocean" title="Ocean">world's seas</a>, <a href="https://en.wikipedia.org/wiki/Sea_ice" title="Sea ice">sea ice</a>, <a href="https://en.wikipedia.org/wiki/Ice_cap" title="Ice cap">icecaps</a> and <a href="https://en.wikipedia.org/wiki/Glacier" title="Glacier">glaciers</a>. It was approved at the IPCC's 51st Session (IPCC-51) in September 2019 in <a href="https://en.wikipedia.org/wiki/Monaco" title="Monaco">Monaco</a>. The SROCC's approved <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Summary_for_policymakers" title="Summary for policymakers">Summary for Policymakers</a> (SPM) was released on 25 September 2019. The 1,300-page report by 104 authors and editors representing 36 countries referred to 6,981 publications.
The report is the third in the series of three Special Reports in the
current Sixth Assessment Report (AR6) cycle, which began in 2015 and
will be completed in 2022. The first was the <a href="https://en.wikipedia.org/wiki/Special_Report_on_Global_Warming_of_1.5_%C2%B0C" title="Special Report on Global Warming of 1.5 °C">Special Report on Global Warming of 1.5 °C</a>, while the second was the <a href="https://en.wikipedia.org/wiki/Special_Report_on_Climate_Change_and_Land" title="Special Report on Climate Change and Land">Special Report on Climate Change and Land</a> (SRCCL), also known as the "Special Report on climate change, <a href="https://en.wikipedia.org/wiki/Desertification" title="Desertification">desertification</a>, <a href="https://en.wikipedia.org/wiki/Land_degradation" title="Land degradation">land degradation</a>, <a href="https://en.wikipedia.org/wiki/Sustainable_land_management" title="Sustainable land management">sustainable land management</a>, <a href="https://en.wikipedia.org/wiki/Food_security" title="Food security">food security</a>, and greenhouse gas fluxes in terrestrial ecosystems", which was released on 7 August 2019.
</p>
<h2><span class="mw-headline" id="Main_statements">Main statements</span></h2><h3><span class="mw-headline" id="SROCC_summary_for_policymakers">SROCC summary for policymakers</span></h3><div class="quotebox pullquote floatright" style="width: 33%;">
<blockquote class="quotebox-quote left-aligned">
<p>"This highlights the urgency of prioritising timely, ambitious, coordinated and enduring action."
</p>
</blockquote>
<p style="padding-bottom: 0em;"><cite class="left-aligned">SRCCL summary for policymakers (SPM)</cite></p>
</div>
<p>In its Summary for Policymakers (SPM), the report said that, since
1970, the "global ocean has warmed unabated" and "has taken up more than
90% of the <a href="https://en.wikipedia.org/wiki/Ocean_heat_content" title="Ocean heat content">excess heat</a> in the climate system." The rate of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_warming" title="Ocean warming">ocean warming</a>
has "more than doubled" since 1993. Marine heatwaves are increasing in
intensity and since 1982, they have "very likely doubled in frequency".
Surface acidification has increased as the oceans absorb more CO<sub>2</sub>. <a href="https://en.wikipedia.org/wiki/Ocean_deoxygenation" title="Ocean deoxygenation">Ocean deoxygenation</a> "has occurred from the surface to 1,000 m (3,300 ft)."
</p>
<h3><span class="mw-headline" id="Rising_sea_levels">Rising sea levels</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Sea_level_rise" title="Sea level rise">Sea level rise</a></div>
<p><a class="new" href="https://en.wikipedia.org/w/index.php?title=Global_mean_sea_levels&action=edit&redlink=1" title="Global mean sea levels (page does not exist)">Global mean sea levels</a> (GMSL) rose by 3.66 mm (0.144 in) per year which is "2.5 times faster than the rate from 1900 to 1990".
At the rate of acceleration, it "could reach around 30 cm (12 in) to
60 cm (24 in) by 2100 even if greenhouse gas emissions are sharply
reduced and global warming is limited to well below 2 °C, but around
60 cm (24 in) to 110 cm (43 in) if emissions continue to increase
strongly. In their summary of the SROCC, <a href="https://en.wikipedia.org/wiki/Carbon_Brief" title="Carbon Brief">Carbon Brief</a> said that rate of <a href="https://en.wikipedia.org/wiki/Sea_level_rise" title="Sea level rise">rising sea levels</a>
is "unprecedented" over the past century. Worst-case projections are
higher than thought and a 2 metres (6.6 ft) rise by 2100 "cannot be
ruled out", if greenhouse gas emissions continue to increase strongly."
</p>
<h3><span class="mw-headline" id="Ocean_deoxygenation">Ocean deoxygenation</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Ocean_deoxygenation" title="Ocean deoxygenation">Ocean deoxygenation</a></div>
<p>The viability of species is being disrupted throughout the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_food_web" title="Ocean food web">ocean food web</a> due to changes in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_chemistry" title="Ocean chemistry">ocean chemistry</a>. As the ocean warms, <a href="https://en.wikipedia.org/wiki/Mixed_layer" title="Mixed layer">mixing between water layers</a> decreases, resulting in less oxygen and nutrients being available for <a href="https://en.wikipedia.org/wiki/Marine_life" title="Marine life">marine life</a>.
</p>
<h3><span class="mw-headline" id="Meridional_overturning_circulation_in_the_Atlantic">Meridional overturning circulation in the Atlantic</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Atlantic_meridional_overturning_circulation" title="Atlantic meridional overturning circulation">Atlantic meridional overturning circulation</a></div>
<p>Chapter 6 which deals with ..., <a href="https://en.wikipedia.org/wiki/Atlantic_meridional_overturning_circulation" title="Atlantic meridional overturning circulation">Atlantic meridional overturning circulation</a> (AMOC) "will very likely weaken over the 21st century" but it is unlikely that AMOC will collapse.
A weakening of AMOC would result in "a decrease in marine productivity
in the North Atlantic, more winter storms in Europe, a reduction in
Sahelian and South Asian summer rainfall, a decrease in the number of
tropical cyclones in the Atlantic, and an increase in regional sea-level
around the Atlantic especially along the northeast coast of North
America." <a href="https://en.wikipedia.org/wiki/Carbon_Brief" title="Carbon Brief">Carbon Brief</a>
described AMOC as "the system of currents in the Atlantic Ocean that
brings warm water up to Europe from the tropics. It is driven by the
formation of North Atlantic Deep Water – the sinking of cold, salty
water in the high latitudes of the North Atlantic."
</p>
<h3><span class="mw-headline" id="Melting_glaciers">Melting glaciers</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850" title="Retreat of glaciers since 1850">Retreat of glaciers since 1850</a></div>
<p>There has been an acceleration of glaciers melting in Greenland and
Antarctica as well as in mountain glaciers around the world, from 2006
to 2015. This now represents a loss of 720 billion tons (653 billion metric tons) of ice a year. </p><p><a href="https://en.wikipedia.org/wiki/Carbon_Brief" title="Carbon Brief">Carbon Brief</a> said that the melting of Greenland's ice sheets is "unprecedented in at least 350 years." The combined melting of Antarctic and <a href="https://en.wikipedia.org/wiki/Greenland_ice_sheet" title="Greenland ice sheet">Greenland ice sheets</a> has contributed "700% more to sea levels" than in the 1990s.
</p>
<h3><span class="mw-headline" id="Arctic_sea_ice_decline">Arctic sea ice decline</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Arctic_sea_ice_decline" title="Arctic sea ice decline">Arctic sea ice decline</a></div>
<p>The <a href="https://en.wikipedia.org/wiki/Arctic_Ocean" title="Arctic Ocean">Arctic Ocean</a>
could be ice free in September "one year in three" if global warming
continues to rise to 2 °C. Prior to industrialization, it was only "once
in every hundred years".
</p>
<h3><span class="mw-headline" id="Global_marine_animal_biomass_and_fish_catch_decline">Global marine animal biomass and fish catch decline</span></h3><div class="quotebox pullquote floatright" style="width: 33%;">
<blockquote class="quotebox-quote left-aligned">
<p>"Since about 1950 many marine species across various groups have
undergone shifts in geographical range and seasonal activities in
response to ocean warming, sea ice change and biogeochemical changes,
such as oxygen loss, to their habitats."
</p>
</blockquote>
<p style="padding-bottom: 0em;"><cite class="left-aligned">SRCCL summary for policymakers (SPM)</cite></p>
</div>
<p>In "Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent
Communities", the authors warn that marine organisms are being affected
by ocean warming with direct impacts on human communities, fisheries,
and food production.<sup class="reference nowrap"><span title="Page / location: 5–6"> </span></sup> The <i>Times</i>
said that it is likely that there will be a 15% decrease in the number
of marine animals and a decrease of 21% to 24% in the "catches by
fisheries in general" by the end of the 21st century because of climate
change.
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<h3><span class="mw-headline" id="Decline_of_snow_and_lake_ice_cover">Decline of snow and lake ice cover</span></h3><p>In
"Chapter 3: Polar Regions", the authors reported that there has been a
decline of snow and lake ice cover. From 1967 to 2018, the extent of
snow in June decreased at a rate of "13.4 ± 5.4% per decade".
</p>
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<h3><span class="mw-headline" id="Thawing_permafrost">Thawing permafrost</span></h3><p>Future climate-induced changes to <a href="https://en.wikipedia.org/wiki/Permafrost" title="Permafrost">permafrost</a> "will drive habitat and biome shifts, with associated changes in the ranges and abundance of ecologically-important species." As <a href="https://en.wikipedia.org/wiki/Permafrost" title="Permafrost">permafrost</a> soil melts, there is a possibility that carbon will be unleashed. The permafrost <a href="https://en.wikipedia.org/wiki/Soil_carbon" title="Soil carbon">soil carbon</a> pool is much "larger than carbon stored in plant biomass".<sup class="reference nowrap"><span title="Page / location: 98"> </span></sup>
"Expert assessment and laboratory soil incubation studies suggest that
substantial quantities of C (tens to hundreds Pg C) could potentially be
transferred from the permafrost carbon pool into the atmosphere under
the <a href="https://en.wikipedia.org/wiki/Representative_Concentration_Pathway" title="Representative Concentration Pathway">Representative Concentration Pathway</a> (RCP) 8.5" projection.
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<h3><span class="mw-headline" id="Low-lying_islands_and_coasts">Low-lying islands and coasts</span></h3><p>In
the final section on low-lying islands and coasts (LLIC), the report
says that cities and megacities—including New York City, Tokyo, Jakarta,
Mumbai, Shanghai, Lagos And Cairo—are "at serious risk from
climate-related ocean and <a href="https://en.wikipedia.org/wiki/Cryosphere" title="Cryosphere">cryosphere</a> changes." If emissions remain high, some low-lying islands are likely to become "uninhabitable" by the end of the 21st century. Low lying areas including islands and the <a href="https://en.wikipedia.org/wiki/Low_Elevation_Coastal_Zone" title="Low Elevation Coastal Zone">Low Elevation Coastal Zone</a>
were estimated have approximately 625 million people living in them
based on 2000 estimates, with most in "non-developed contexts."
</p>
<h2><span class="mw-headline" id="Reactions">Reactions</span></h2><p><i><a href="https://en.wikipedia.org/wiki/The_New_York_Times" title="The New York Times">The New York Times</a></i> headlined their 25 September article with "We're All in Big Trouble". According to the <i>Times</i>, "Sea levels are rising at an ever-faster rate as ice and snow shrink, and oceans are getting more acidic and losing oxygen." The article cited <a href="https://en.wikipedia.org/wiki/Princeton_University" title="Princeton University">Princeton University</a>'s <a href="https://en.wikipedia.org/wiki/Michael_Oppenheimer" title="Michael Oppenheimer">Michael Oppenheimer</a>,
who was one of the report's lead authors who said that, "The oceans and
the icy parts of the world are in big trouble, and that means we're all
in big trouble, too. The changes are accelerating." IPCC Working Group I Co-Chair, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Val%C3%A9rie_Masson-Delmotte" title="Valérie Masson-Delmotte">Valérie Masson-Delmotte</a>,
was quoted as saying in Monaco, that "Climate change is already
irreversible. Due to the heat uptake in the ocean, we can't go back."
</p><p>The <a href="https://en.wikipedia.org/wiki/BBC" title="BBC">BBC</a> headline referred to a red alert on the <a href="https://en.wikipedia.org/wiki/Earth" title="Earth">Blue Planet</a>.
</p><p><i><a href="https://en.wikipedia.org/wiki/The_Economist" title="The Economist">The Economist</a></i> said that the "world's oceans are getting warmer, stormier and more acidic. They are becoming less productive as the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ecosystems" title="Ecosystems">ecosystems</a>
within them collapse. Melting glaciers and ice sheets are causing sea
levels to rise, increasing the risk of inundation and devastation to
hundreds of millions of people living in coastal areas."
</p><p><i><a href="https://en.wikipedia.org/wiki/PBS_NewsHour" title="PBS NewsHour">PBS NewsHour</a></i> cited <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">National Oceanic and Atmospheric Administration</a>'s (NOAA) <a class="new" href="https://en.wikipedia.org/w/index.php?title=Ko_Barrett&action=edit&redlink=1" title="Ko Barrett (page does not exist)">Ko Barrett</a>,
who is also a vice chair of IPCC, saying, "Taken together, these
changes show that the world's ocean and cryosphere have been taking the
heat for climate change for decades. The consequences for nature are
sweeping and severe."
</p><p><i><a href="https://en.wikipedia.org/wiki/The_Atlantic" title="The Atlantic">The Atlantic</a></i> called it a blockbuster report.
</p><p><i><a href="https://en.wikipedia.org/wiki/National_Geographic" title="National Geographic">National Geographic</a></i>
said that according to the report, "These challenges are only going to
get worse unless countries make lightning-fast moves to eliminate
greenhouse gas emissions... But strong, decisive action could still
forestall or evade some of the worst impacts."</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-62205780842745893402024-03-17T16:37:00.005-04:002024-03-17T16:37:46.555-04:00Ocean deoxygenation<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Ocean_deoxygenation">https://en.wikipedia.org/wiki/Ocean_deoxygenation</a><br /></div>
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<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Global_areas_of_hypoxia.jpg"><img class="mw-file-element" data-file-height="613" data-file-width="1350" height="200" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Global_areas_of_hypoxia.jpg/440px-Global_areas_of_hypoxia.jpg" width="440" /></a><figcaption>Global map of low and declining oxygen levels in coastal waters (mainly due to <a href="https://en.wikipedia.org/wiki/Eutrophication" title="Eutrophication">eutrophication</a>) and in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Open_ocean" title="Open ocean">open ocean</a> (due to <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans">climate change</a>). The map indicates coastal sites where oxygen levels have declined to less than 2 mg/L (red dots), as well as expanding ocean <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a> at 300 metres (blue shaded regions).</figcaption></figure>
<p><b>Ocean deoxygenation</b> is the reduction of the <a href="https://en.wikipedia.org/wiki/Oxygen_saturation" title="Oxygen saturation">oxygen content</a> in different parts of the <a href="https://en.wikipedia.org/wiki/Ocean" title="Ocean">ocean</a> due to human activities. It occurs firstly in <a href="https://en.wikipedia.org/wiki/Coast" title="Coast">coastal zones</a> where <a href="https://en.wikipedia.org/wiki/Eutrophication" title="Eutrophication">eutrophication</a> has driven some quite rapid (in a few decades) declines in oxygen to very low levels. This type of ocean deoxygenation is also called "<a href="https://en.wikipedia.org/wiki/Dead_zone_(ecology)" title="Dead zone (ecology)">dead zones</a>".
Secondly, there is now an ongoing reduction in oxygen levels in the
open ocean: naturally occurring low oxygen areas (so called <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a> (OMZs)) are now expanding slowly. This expansion is happening as a consequence of human caused <a href="https://en.wikipedia.org/wiki/Climate_change" title="Climate change">climate change</a>. The resulting decrease in oxygen content of the oceans poses a threat to <a href="https://en.wikipedia.org/wiki/Marine_life" title="Marine life">marine life</a>, as well as to people who depend on marine life for nutrition or livelihood. Ocean deoxygenation poses implications for <a href="https://en.wikipedia.org/wiki/Primary_production" title="Primary production">ocean productivity</a>, nutrient cycling, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_cycling" title="Carbon cycling">carbon cycling</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marine_habitats" title="Marine habitats">marine habitats</a>.
</p><p><a href="https://en.wikipedia.org/wiki/Ocean_heat_content" title="Ocean heat content">Ocean warming</a> exacerbates ocean deoxygenation and further stresses marine organisms, reducing nutrient availability by increasing <a href="https://en.wikipedia.org/wiki/Ocean_stratification" title="Ocean stratification">ocean stratification</a> through density and solubility effects while at the same time increasing metabolic demand.
The rising temperatures in the oceans cause a reduced solubility of
oxygen in the water, which can explain about 50% of oxygen loss in the
upper level of the ocean (>1000 m). Warmer ocean water holds less
oxygen and is more buoyant than cooler water. This leads to reduced
mixing of oxygenated water near the surface with deeper water, which
naturally contains less oxygen. Warmer water also raises oxygen demand
from living organisms; as a result, less oxygen is available for marine
life.
</p><p>Studies have shown that oceans have already lost 1-2% of their oxygen since the middle of the 20th century, and model simulations predict a decline of up to 7% in the global ocean O<sub>2</sub> content over the next hundred years. The decline of oxygen is projected to continue for a thousand years or more.
</p>
<h2><span class="mw-headline" id="Terminology">Terminology</span></h2></div></div></div><p>The term <i>ocean deoxygenation</i>
has been used increasingly by international scientific bodies because
it captures the decreasing trend of the world ocean's oxygen inventory.
Oceanographers and others have discussed what phrase best describes the
phenomenon to non-specialists. Among the options considered have been <i>ocean suffocation</i>, <i>ocean oxygen deprivation</i>, <i>decline in ocean oxygen</i>, <i>marine deoxygenation</i>, <i>ocean oxygen depletion</i> and <i>ocean <a href="https://en.wikipedia.org/wiki/Hypoxia_(environmental)" title="Hypoxia (environmental)">hypoxia</a></i>.
</p>
<h2><span class="mw-headline" id="Types_and_mechanisms">Types and mechanisms</span></h2><p>There
are two types of ocean deoxygenation, taking place in two different
zones and having different causes: the reduction of oxygen in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Coastal_zone" title="Coastal zone">coastal zones</a> versus in the open ocean as well as deep ocean (<a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a>). These are coupled but different.
</p>
<h3><span class="mw-headline" id="Coastal_zones">Coastal zones</span></h3><div class="excerpt-block"><div class="excerpt">
<figure class="mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Aquatic_Dead_Zones.jpg"><img class="mw-file-element" data-file-height="2094" data-file-width="3577" height="234" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Aquatic_Dead_Zones.jpg/400px-Aquatic_Dead_Zones.jpg" width="400" /></a><figcaption>Red
circles show the location and size of many dead zones (in 2008). Black
dots show dead zones of unknown size. The size and number of marine dead
zones—areas where the deep water is so low in dissolved oxygen that sea
creatures cannot survive (except for some specialized bacteria)—have
grown in the past half-century.</figcaption></figure>
Coastal regions, such as the <a href="https://en.wikipedia.org/wiki/Baltic_Sea" title="Baltic Sea">Baltic Sea</a>, the northern <a href="https://en.wikipedia.org/wiki/Gulf_of_Mexico" title="Gulf of Mexico">Gulf of Mexico</a>, and the <a href="https://en.wikipedia.org/wiki/Chesapeake_Bay" title="Chesapeake Bay">Chesapeake Bay</a>, as well as large enclosed water bodies like <a href="https://en.wikipedia.org/wiki/Lake_Erie" title="Lake Erie">Lake Erie</a>, have been affected by deoxygenation due to <a href="https://en.wikipedia.org/wiki/Eutrophication" title="Eutrophication">eutrophication</a>.
Excess nutrients are input into these systems by rivers, ultimately
from urban and agricultural runoff and exacerbated by deforestation.
These nutrients lead to high productivity that produces organic material
that sinks to the bottom and is respired. The respiration of that
organic material uses up the oxygen and causes <a href="https://en.wikipedia.org/wiki/Hypoxia_(environmental)" title="Hypoxia (environmental)">hypoxia</a> or <a href="https://en.wikipedia.org/wiki/Anoxic_waters" title="Anoxic waters">anoxia</a>.</div></div>
<h3><span id="Open_and_deep_ocean_zones_.28oxygen_minimum_zones.29"></span><span class="mw-headline" id="Open_and_deep_ocean_zones_(oxygen_minimum_zones)">Open and deep ocean zones (oxygen minimum zones)</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans">Effects of climate change on oceans</a>, <a href="https://en.wikipedia.org/wiki/Ocean_stratification" title="Ocean stratification">Ocean stratification</a>, and <a href="https://en.wikipedia.org/wiki/Ocean_heat_content" title="Ocean heat content">Ocean heat content</a></div>
<p>In the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Open_ocean" title="Open ocean">open ocean</a> there are natural low oxygen areas and these are expanding slowly. These oceanic <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a>
(OMZ) generally occur in the middle depths of the ocean, from 100 –
1000 m deep. They are natural phenomena that result from respiration of
sinking organic material produced in the surface ocean. However, as the
oxygen content of the ocean decreases, oxygen minimum zones are
expanding both vertically and horizontally.
In these low oxygen areas the water circulation is slow. This stability
means it is easier to see quite small changes in oxygen, such as a
decline of 1-2%. In many of these areas, this decline does not mean
these low oxygen regions become uninhabitable for fish and other marine
life but over many decades may do, particularly in the Pacific and
Indian Ocean.
</p><p>Oxygen is input into the ocean at the surface, through the processes of <a href="https://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a> by <a href="https://en.wikipedia.org/wiki/Phytoplankton" title="Phytoplankton">phytoplankton</a>
and mixing with the atmosphere. Organisms, both microbial and
multicellular, use oxygen in respiration throughout the entire depth of
the ocean, so when the supply of oxygen from the surface is less than
the utilization of oxygen in deep water, oxygen loss occurs.
</p><p>This phenomenon is natural, but is exacerbated with increased <a href="https://en.wikipedia.org/wiki/Ocean_stratification" title="Ocean stratification">stratification</a> and increasing <a href="https://en.wikipedia.org/wiki/Ocean_temperature" title="Ocean temperature">ocean temperature</a>. Stratification occurs when water masses with different properties, primarily temperature and <a href="https://en.wikipedia.org/wiki/Salinity" title="Salinity">salinity</a>,
are layered, with lower density water on top of higher density water.
The larger the differences in the properties between layers, the less
mixing occurs between the layers. Stratification is increased when the
temperature of the surface ocean or the amount of freshwater input into
the ocean from rivers and ice melt increases, enhancing ocean
deoxygenation by reducing supply. Another factor that can reduce supply
is the <a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">solubility</a>
of oxygen. As temperature and salinity increase, the solubility of
oxygen decreases, meaning that less oxygen can be dissolved into water
as it warms and becomes more salty.
</p>
<h2><span class="mw-headline" id="Role_of_climate_change">Role of climate change</span></h2><p>While oxygen minimum zones (OMZs) occur naturally, they can be exacerbated by human impacts like <a href="https://en.wikipedia.org/wiki/Climate_change" title="Climate change">climate change</a> and land-based pollution from agriculture and sewage. The prediction of current <a href="https://en.wikipedia.org/wiki/Climate_model" title="Climate model">climate models</a> and <a href="https://en.wikipedia.org/wiki/Climate_change_scenario" title="Climate change scenario">climate change scenarios</a> is that substantial warming and loss of oxygen throughout the majority of the upper ocean will occur.
Global warming increases ocean temperatures, especially in shallow
coastal areas. When the water temperature increases, its ability to hold
oxygen decreases, leading to oxygen concentrations going down in the
water. This compounds the effects of eutrophication in coastal zones described above.
</p><p>Open ocean areas with no oxygen have grown more than 1.7 million
square miles in the last 50 years, and coastal waters have seen a
tenfold increase in low-oxygen areas in the same time.
</p><p>Measurement of dissolved oxygen in coastal and open ocean waters
for the past 50 years has revealed a marked decline in oxygen content.
This decline is associated with expanding spatial extent, expanding
vertical extent, and prolonged duration of oxygen-poor conditions in all
regions of the global oceans. Examinations of the spatial extent of
OMZs in the past through paleoceanographical methods clearly shows that
the spatial extent of OMZs has expanded through time, and this expansion
is coupled to ocean warming and reduced ventilation of thermocline
waters.
</p><p>Research has attempted to model potential changes to OMZs as a
result of rising global temperatures and human impact. This is
challenging due to the many factors that could contribute to changes in
OMZs. The factors used for modeling change in OMZs are numerous, and in some cases hard to measure or quantify.
Some of the processes being studied are changes in oxygen gas
solubility as a result of rising ocean temperatures, as well as changes
in the amount of respiration and photosynthesis occurring around OMZs.
Many studies have concluded that OMZs are expanding in multiple
locations, but fluctuations of modern OMZs are still not fully
understood. Existing <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Earth_system_model" title="Earth system model">Earth system models</a> project considerable reductions in oxygen and other physical-chemical variables in the ocean due to <a href="https://en.wikipedia.org/wiki/Climate_change" title="Climate change">climate change</a>, with potential ramifications for <a href="https://en.wikipedia.org/wiki/Ecosystem" title="Ecosystem">ecosystems</a> and humans.
</p><p>The global decrease in oceanic oxygen content is statistically
significant and emerging beyond the envelope of natural fluctuations. This trend of oxygen loss is accelerating, with widespread and obvious losses occurring after the 1980s.
The rate and total content of oxygen loss varies by region, with the
North Pacific emerging as a particular hotspot of deoxygenation due to
the increased amount of time since its deep waters were last ventilated
(see thermohaline circulation) and related high apparent oxygen
utilization (AOU). Estimates of total oxygen loss in the global ocean range from 119 to 680 T mol decade<sup>−1</sup> since the 1950s. These estimates represent 2% of the global ocean oxygen inventory.
</p><p>Melting of gas hydrates in bottom layers of water may result in
the release of more methane from sediments and subsequent consumption of
oxygen by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Aerobic_respiration" title="Aerobic respiration">aerobic respiration</a> of methane to <a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a>. Another <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans">effect of climate change on oceans</a>
that causes ocean deoxygenation is circulation changes. As the ocean
warms from the surface, stratification is expected to increase, which
shows a tendency for slowing down ocean circulation, which then
increases ocean deoxygenation.
</p>
<h3><span class="mw-headline" id="Estimates_for_the_future">Estimates for the future</span></h3><p>The results from mathematical models show that global ocean oxygen loss rates will continue to accelerate up to 125 T mol year<sup>−1</sup>
by 2100 due to persistent warming, a reduction in ventilation of deeper
waters, increased biological oxygen demand, and the associated
expansion of OMZs into shallower areas.
</p>
<h2><span class="mw-headline" id="Variations">Variations</span></h2><h3><span id="Expanding_oxygen_minimum_zones_.28OMZ.29"></span><span class="mw-headline" id="Expanding_oxygen_minimum_zones_(OMZ)">Expanding oxygen minimum zones (OMZ)</span></h3><p>Several
areas of the open ocean have naturally low oxygen concentration due to
biological oxygen consumption that cannot be supported by the rate of
oxygen input to the area from physical transport, air-sea mixing, or
photosynthesis. These areas are called <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a>
(OMZs), and there is a wide variety of open ocean systems that
experience these naturally low oxygen conditions, such as upwelling
zones, deep basins of enclosed seas, and the cores of some mode-water
eddies.
</p><p>Ocean deoxygenation has led to suboxic, hypoxic, and anoxic conditions in both <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Coastal_waters" title="Coastal waters">coastal waters</a> and the open ocean. Since 1950, more than 500 sites in coastal waters have reported oxygen concentrations below 2 mg liter<sup>−1</sup>, which is generally accepted as the threshold of hypoxic conditions.
</p><p>The extent of OMZs has expanded in tropical oceans during the past half century.
</p><p>Oxygen-poor waters of coastal and open ocean systems have largely
been studied in isolation of each other, with researchers focusing on
eutrophication-induced hypoxia in coastal waters and naturally occurring
(without apparent direct input of anthropogenic nutrients) open ocean
OMZs. However, coastal and open ocean oxygen-poor waters are highly
interconnected and therefore both have seen an increase in the
intensity, spatial extent, and temporal extent of deoxygenated
conditions.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg"><img class="mw-file-element" data-file-height="348" data-file-width="429" height="324" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg/370px-Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg.png" width="400" /></a><figcaption>Drivers of <a href="https://en.wikipedia.org/wiki/Hypoxia_(environmental)" title="Hypoxia (environmental)">hypoxia</a> and ocean acidification intensification in <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a> shelf systems. Equatorward winds drive the upwelling of low <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dissolved_oxygen" title="Dissolved oxygen">dissolved oxygen</a> (DO), high nutrient, and high <a href="https://en.wikipedia.org/wiki/Dissolved_inorganic_carbon" title="Dissolved inorganic carbon">dissolved inorganic carbon</a> (DIC) water from above the <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zone</a>.
Cross-shelf gradients in productivity and bottom water residence times
drive the strength of DO (DIC) decrease (increase) as water transits
across a productive <a href="https://en.wikipedia.org/wiki/Continental_shelf" title="Continental shelf">continental shelf</a>.</figcaption></figure>
<p>The spatial extent of deoxygenated conditions can vary widely. In
coastal waters, regions with deoxygenated conditions can extend from
less than one to many thousands of square kilometers.
Open ocean OMZs exist in all ocean basins and have similar variation in
spatial extent; an estimated 8% of global ocean volume is within OMZs.
The largest OMZ is in the eastern tropical north Pacific and comprises
41% of this global volume, and the smallest OMZ is found in the eastern tropical North Atlantic and makes up only 5% of the global OMZ volume.
</p>
<h3><span class="mw-headline" id="Vertical_extent_of_low_oxygen_conditions">Vertical extent of low oxygen conditions</span></h3><p>The
vertical extent of low oxygen conditions is also variable, and areas of
persistent low oxygen have annual variation in the upper and lower
limits of oxygen-poor waters.
Typically, OMZs are expected to occur at depths of about 200 to 1,000
meters. The upper limit of OMZs is characterized by a strong and rapid
gradient in oxygenation, called the oxycline.
The depth of the oxycline varies between OMZs, and is mainly affected
by physical processes such as air-sea fluxes and vertical movement in
the thermocline depth.
The lower limit of OMZs is associated with the reduction in biological
oxygen consumption, as the majority of organic matter is consumed and
respired in the top 1,000 m of the vertical water column. Shallower
coastal systems may see oxygen-poor waters extend to bottom waters,
leading to negative effects on benthic communities.
</p><p>Many persistent OMZs have increased in thickness over the last
five decades. This happened because the upper limit of the OMZ became
shallower and also because the OMZ expanded downward.
</p>
<h3><span class="mw-headline" id="Variations_in_temporal_duration">Variations in temporal duration</span></h3><p>The
temporal duration of oxygen-poor conditions can vary on seasonal,
annual, or multi-decadal scales. Hypoxic conditions in coastal systems
like the Gulf of Mexico are usually tied to discharges of rivers,
thermohaline stratification of the water column, wind-driven forcing,
and continental shelf circulation patterns. As such, there are seasonal and annual patterns in the initiation, persistence, and break down of intensely hypoxic conditions.
Oxygen concentrations in open oceans and the margins between coastal
areas and the open ocean may see variation in intensity, spatial extent,
and temporal extent from multi-decadal oscillations in climatic
conditions.
</p><p>Coastal regions have also seen expanded spatial extent and
temporal duration due to increased anthropogenic nutrient input and
changes in regional circulation.
Areas that have not previously experienced low oxygen conditions, like
the coastal shelf of Oregon on the West coast of the United States, have
recently and abruptly developed seasonal hypoxia.
</p>
<h2><span class="mw-headline" id="Impacts">Impacts</span></h2><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans">Effects of climate change on oceans</a></div>
<p>Ocean deoxygenation poses implications for <a href="https://en.wikipedia.org/wiki/Primary_production" title="Primary production">ocean productivity</a>, nutrient cycling, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_cycling" title="Carbon cycling">carbon cycling</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marine_habitats" title="Marine habitats">marine habitats</a>. Studies have shown that oceans have already lost 1-2% of their oxygen since the middle of the 20th century, and model simulations predict a decline of up to 7% in the global ocean O<sub>2</sub> content over the next hundred years. The decline of oxygen is projected to continue for a thousand years or more.
</p><p>The viability of species is being disrupted throughout the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_food_web" title="Ocean food web">ocean food web</a> due to changes in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_chemistry" title="Ocean chemistry">ocean chemistry</a>. As the ocean warms, <a href="https://en.wikipedia.org/wiki/Mixed_layer" title="Mixed layer">mixing between water layers</a> decreases, resulting in less oxygen and nutrients being available for <a href="https://en.wikipedia.org/wiki/Marine_life" title="Marine life">marine life</a>.
</p><p>Ocean deoxygenation is an additional stressor on <a href="https://en.wikipedia.org/wiki/Marine_life" title="Marine life">marine life</a>. Ocean deoxygenation results in the expansion of <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zones</a>
in the oceans . Along with this ocean deoxygenation is caused by an
imbalance of sources and sinks of oxygen in dissolved water.
The change has been fairly rapid and poses a threat to fish and other
types of marine life, as well as to people who depend on marine life for
nutrition or livelihood. Ocean deoxygenation poses implications for <a href="https://en.wikipedia.org/wiki/Primary_production" title="Primary production">ocean productivity</a>, nutrient cycling, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_cycling" title="Carbon cycling">carbon cycling</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marine_habitats" title="Marine habitats">marine habitats</a>.
</p><p>As low oxygen zones expand vertically nearer to the surface, they can affect <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Coastal_upwelling" title="Coastal upwelling">coastal upwelling</a> systems such as the <a href="https://en.wikipedia.org/wiki/California_Current" title="California Current">California Current</a> on the coast of <a href="https://en.wikipedia.org/wiki/Oregon" title="Oregon">Oregon</a>
(US). These upwelling systems are driven by seasonal winds that force
the surface waters near the coast to move offshore, which pulls deeper
water up along the <a href="https://en.wikipedia.org/wiki/Continental_shelf" title="Continental shelf">continental shelf</a>.
As the depth of the deoxygenated deeper water becomes shallower, more
of the deoxygenated water can reach the continental shelf, causing
coastal hypoxia and fish kills. Impacts of massive fish kills on the <a href="https://en.wikipedia.org/wiki/Aquaculture" title="Aquaculture">aquaculture</a> industry are projected to be profound.
</p>
<h3><span class="mw-headline" id="Marine_organisms_and_biodiversity">Marine organisms and biodiversity</span></h3><p>Short
term effects can be seen in acutely fatal circumstances, but other
sublethal consequences can include impaired reproductive ability,
reduced growth, and increase in diseased population.
These can be attributed to the co-stressor effect. When an organism is
already stressed, for example getting less oxygen than it would prefer,
it does not do as well in other areas of its existence like
reproduction, growth, and warding off disease.
Additionally, warmer water not only holds less oxygen, but it also
causes marine organisms to have higher metabolic rates, resulting in
them using up available oxygen more quickly, lowering the oxygen
concentration in the water even more and compounding the effects seen.
Finally, for some organisms, habitat reduction will be a problem.
Habitable zones in the water column are expected to compress and
habitable seasons are expected to be shortened. If the water an
organism's regular habitat sits in has oxygen concentrations lower than
it can tolerate, it will not want to live there anymore. This leads to
changed migration patterns as well as changed or reduced habitat area.
</p><p>Long term effects can be seen on a broader scale of changes in <a href="https://en.wikipedia.org/wiki/Biodiversity" title="Biodiversity">biodiversity</a>
and food web makeup. Due to habitat change of many organisms,
predator-prey relationships will be altered. For example, when squeezed
into a smaller well-oxygenated area, predator-prey encounter rates will
increase, causing an increase in <a href="https://en.wikipedia.org/wiki/Predation" title="Predation">predation</a>, potentially putting strain on the prey population. Additionally, diversity of ecosystems in general is expected to decrease due to decrease in oxygen concentrations.
</p>
<h3><span class="mw-headline" id="Effects_on_fisheries">Effects on fisheries</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Microbiology_of_oxygen_minimum_zones" title="Microbiology of oxygen minimum zones">Microbiology of oxygen minimum zones</a> and <a href="https://en.wikipedia.org/wiki/Human_impact_on_marine_life" title="Human impact on marine life">Human impact on marine life</a></div>
<p>Vertical expansion of tropical OMZs has reduced the area between the OMZ and surface.
This means that many species that live near the surface, such as fish,
could be affected periodically. Ongoing research is investigating how
OMZ expansion affects food webs in these areas.
Studies on OMZ expansion in the tropical Pacific and Atlantic have
observed negative effects on fish populations and commercial fisheries
that likely occurred from reduced habitat when the OMZ moved to a
shallower depth.
</p><p>A fish's behavior in response to ocean deoxygenation is based
upon their tolerance to oxygen poor conditions. Species with low anoxic
tolerance tend to undergo habitat compression in response to the
expansion of OMZs.
Fish species with a low tolerance for low oxygen conditions may move to
live nearer the ocean surface where oxygen concentration will usually
be higher.
Biological responses to habitat compression can be varied. Some species
of billfish, predatory pelagic predators such as sailfish and marlin,
that have undergone habitat compression actually have increased growth
since their prey, smaller pelagic fish, experienced the same habitat
compression, resulting in increased prey vulnerability to billfishes.
Fish with tolerance to anoxic conditions, such as jumbo squid and
lanternfish, can remain active in anoxic environments at a reduced
level, which can improve their survival by increasing avoidance of
anoxia intolerant predators and have increased access to resources that
their anoxia intolerant competitors cannot.
</p><p>The relationship between zooplankton and low oxygen zones is
complex and varies by species and life stage. Some gelatinous
zooplankton reduce their growth rates when exposed to hypoxia while
others utilize this habitat to forage on high prey concentrations with
their growth rates unaffected.
The ability of some gelatinous zooplankton to tolerate hypoxia may be
attributed to the ability to store oxygen in intragel regions.
The movements of zooplankton as a result of ocean deoxygenation can
affect fisheries, global nitrogen cycling, and trophic relationships.
These changes have the potential to have large economic and
environmental consequences through overfishing or collapsed food webs.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-47873059096414778802024-03-17T08:47:00.003-04:002024-03-17T08:47:34.063-04:00Free Ocean CO2 Enrichment<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Free_Ocean_CO2_Enrichment">https://en.wikipedia.org/wiki/Free_Ocean_CO2_Enrichment</a><br /></div>
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<p><b>Free Ocean CO<sub>2</sub> Enrichment</b> (<b>FOCE</b>) is a technology facilitating studies of the consequences of <a href="https://en.wikipedia.org/wiki/Ocean_acidification" title="Ocean acidification">ocean acidification</a> for marine organisms and communities by enabling the precise control of CO<sub>2</sub> enrichment within in situ, partially open, experimental enclosures. Current FOCE systems control experimental CO<sub>2</sub> perturbations by real-time monitoring of differences in seawater pH between treatment (i.e. high-CO<sub>2</sub>) and control (i.e. ambient) seawater within experimental enclosures.
</p>
<h2><span class="mw-headline" id="Overview">Overview</span></h2></div></div></div><p>In
situ, controlled perturbation experiments, often conducted over weeks
to months, can provide inference concerning the response of natural
communities to ocean acidification that is difficult or impossible to
derive from laboratory experiments. Studies conducted in situ can
include the effects of potentially important factors such as natural
variation in planktonic food resources, larval abundance, changes in
predators or competitors, as well as oceanographic conditions (e.g.
changes in upwelling intensity). Drawing on the experience of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Free-Air_Concentration_Enrichment" title="Free-Air Concentration Enrichment">Free Air CO<sub>2</sub> Enrichment</a> (FACE) experiments used to investigate the response of terrestrial plant communities to rising atmospheric CO<sub>2</sub> levels, the scientific community has developed an analogous approach, Free Ocean CO<sub>2</sub>
Enrichment (FOCE) experiments, for studying marine communities, and to
complement a range of experimental methods and technologies for ocean
acidification studies research. FOCE was first proposed and implemented
by researchers at the <a href="https://en.wikipedia.org/wiki/Monterey_Bay_Aquarium_Research_Institute" title="Monterey Bay Aquarium Research Institute">Monterey Bay Aquarium Research Institute</a> (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/MBARI" title="MBARI">MBARI</a>).
</p>
<h2><span class="mw-headline" id="Purpose">Purpose</span></h2><p>As
studies of the consequences of ocean acidification for marine organisms
and ecosystems expanded rapidly over the past decade, the methods
employed to evaluate the effects of expected future changes in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_chemistry" title="Ocean chemistry">ocean chemistry</a>
have become more sophisticated. Initial studies frequently involved
measurements of the survival or physiological response of individuals of
marine species to large changes in pCO2 or pH, while held in small
containers under laboratory conditions. This approach increased the
level of understanding of the effects of these environmental changes on
individual species but provided little information concerning the
response of natural assemblages of interacting species, in which the
direct impacts of ocean acidification as well as their cascading
indirect consequences (e.g. changes in the intensity of interaction
strengths among predators or competitors) may be evident. Pelagic
mesocosm experiments that examined the response of natural plankton
communities to controlled pH perturbations helped move methods of ocean
acidification research toward more comprehensive studies of whole
communities and embedded processes under mostly natural conditions.
The FOCE approach represents an analogous advance for benthic
assemblages, by allowing examination of the direct effects of
acidification on particular species, but also potential changes in
interactions among species. Moreover, FOCE methods provide precise
control of pH, while allowing many other parameters to vary naturally.
Like mesocosm studies, FOCE methods exploit the advantages of studying a
natural community under mostly natural ranges of environmental
variability.
</p>
<h2><span class="mw-headline" id="Methods">Methods</span></h2><p>The key elements of any FOCE experimental units are perspex, partially open, chambers, a CO<sub>2</sub>
mixing system, sensors to continuously monitor ambient and chamber pH,
and a control loop to regulate the addition of gases or liquids to each
experimental chamber.
</p><p>The carbonate chemistry of seawater can be manipulated using different approaches to mimic future conditions. It is possible to directly inject gases (pure CO<sub>2</sub> or CO<sub>2</sub>-enriched
air) but this is more difficult than delivering water to achieve
precise pH control. Current FOCE systems lower pH using metered addition
of CO<sub>2</sub>-enriched seawater into the experimental chambers. pH
is controlled as a constant pH offset relative to ambient values,
maintaining natural variability, or as a constant value.
</p><p>Other approaches have been used to manipulate the seawater carbonate chemistry in the field. In pelagic mesocosm experiments,
the carbonate chemistry is generally altered at the beginning of the
experiment and subsequently drifts as a function of biological processes
and air-sea gas transfer. CO<sub>2</sub> bubbling in open water has also been used.
This approach does not enable precise control of the carbonate
chemistry because it does not include a device to ensure full
equilibration of added CO<sub>2</sub> in seawater and its precise
control. There are no experimental chambers to regulate water flow, and
thus allows for natural near-bottom flow conditions, but it generates
highly variable pH under variable current speed or direction. This
approach is therefore more similar to natural CO<sub>2</sub> vents than
to FOCE systems. This approach can be useful when organisms can not be
enclosed in chambers and when they inhabit environments such as
estuaries where pCO2 levels are naturally hyper-variable. The approach
has inherent limitations but may allow greater replication, at lower
cost.
</p><p>Current users of FOCE systems have organized to release
guidelines and best practices information for future users. Furthermore,
the Monterey Bay Aquarium Research Institute will release an open
source package to transfer FOCE technology to interested researchers (<a class="external text" href="http://www.xfoce.org" rel="nofollow">xFOCE</a>). This package will comprise all engineering information required to develop cost effective FOCE systems.
</p><p>Future development of FOCE systems will include the study of the
combined effects of ocean acidification and other environmental factors
such as temperature or the concentration of dissolved oxygen.
</p>
<h2><span class="mw-headline" id="Current_FOCE_Projects">Current FOCE Projects</span></h2><h3><span id="Deep_FOCE_.28dpFOCE.29"></span><span class="mw-headline" id="Deep_FOCE_(dpFOCE)">Deep FOCE (dpFOCE)</span></h3><p>A
FOCE system for studies of deep-sea benthic communities (designated
dp-FOCE) was developed by Monterey Bay Aquarium Research Institute. The
dpFOCE project, deployed at a depth of 900 m, was attached to the MARS
cabled seafloor observatory in Monterey Bay, central California. The
system used a flume concept for maintaining greater control over the
experimental volume while still maintaining access to natural seafloor
sediments and suspended particulate material. Time-delay wings attached
to either end of the dpFOCE chamber allow for tidally driven changes in
near-bottom currents, and provide sufficient time for full hydration of
the injected CO<sub>2</sub> enriched seawater before entering into the
experiment chamber. Fans are integrated into the dpFOCE design to
control flow rates through the experimental chamber and to simulate
typical local-scale flow conditions. Multiple sensors (pH, CTD, ADV, and
ADCP) used in conjunction with the fans and the enriched seawater
injection system allow the control loop software to achieve the desired
pH offset. dpFOCE connects to shore via the MARS cabled observatory,
which provides power and data bandwidth. Enriched CO<sub>2</sub> seawater is produced from liquid CO<sub>2</sub> held in a small container near the dpFOCE chamber; seawater flowing slowly over the top of the liquid CO<sub>2</sub> dissolves some of the liquid CO<sub>2</sub> producing a CO<sub>2</sub>-rich
dissolution plume used for injection into the dpFOCE chamber. The
dpFOCE system operated over 17 months and verified the effectiveness of
the design hardware and software.
</p>
<h3><span id="Coral_Prototype_FOCE_.28cpFOCE.29"></span><span class="mw-headline" id="Coral_Prototype_FOCE_(cpFOCE)">Coral Prototype FOCE (cpFOCE)</span></h3><p>The cpFOCE uses replicate experimental flumes to enclose sections of a coral reef and dose them with CO<sub>2</sub>-enriched
seawater using peristaltic pumps with computer controlled feedback loop
to maintain a specified pH offset from ambient conditions. A cpFOCE
chamber has forward and rear flow conditioners on either end to
accommodate bidirectional ocean currents. The openings are placed
parallel to the dominant axis of tidal currents over the reef flat, and
the chamber is anchored with sand stakes. The flow conditioners are
attached to maximize turbulence and provide passive mixing of the CO<sub>2</sub>
enriched seawater. Four of the tubes in the flow conditioners furthest
from the chamber have small holes along their length through which low
pH water is pumped to dispense it evenly along the entire width and
height of the conditioner. The flow conditioners are also painted white
to minimize heating and algal growth. The cpFOCE system was deployed at
Heron Island (<a href="https://en.wikipedia.org/wiki/Great_Barrier_Reef" title="Great Barrier Reef">Great Barrier Reef</a>) to investigate the response of coral communities to ocean acidification.
</p>
<h3><span id="European_FOCE_.28eFOCE.29"></span><span class="mw-headline" id="European_FOCE_(eFOCE)">European FOCE (eFOCE)</span></h3><p>The European FOCE (<a class="external text" href="http://efoce.eu" rel="nofollow">eFOCE</a>)
comprises two open-top chambers (control and experimental) as well as a
surface buoy housing the electronics and pumps to produce CO<sub>2</sub>-enriched
water. The system is powered by solar and wind energy. Data packets are
wirelessly sent to the nearby laboratory and can be monitored on the
internet. The eFOCE system is currently deployed in the bay of
Villefranche-sur-mer (France) at about 12 m depth and 300 m offshore.
The eFOCE project has been developed to investigate the long-term
effects of acidification on benthic marine communities of the North West
Mediterranean Sea, especially Posidonia seagrass beds. Over a 3-year
period, the aim of the project is to develop relatively long (>
6 month) experiments.
</p>
<h3><span id="Shallow_Water_FOCE_.28swFOCE.29"></span><span class="mw-headline" id="Shallow_Water_FOCE_(swFOCE)">Shallow Water FOCE (swFOCE)</span></h3><p>In collaboration with <a href="https://en.wikipedia.org/wiki/Hopkins_Marine_Station" title="Hopkins Marine Station">Hopkins Marine Station</a>
and the Center for Ocean Solutions, Monterey Bay Aquarium Research
Institute is developing a swFOCE system to examine the effects of ocean
acidification on shallow subtidal communities in central California.
swFOCE will use a shore side station for the control system and
production of CO<sub>2</sub> enriched seawater, and will also use and
will use an existing cabled observational and research platform to
connect the swFOCE node. Two swFOCE chambers will be installed initially
at a depth of 15 m, approximately 250 m offshore. The nearby node of
the cabled observatorynode, has instruments to monitor local currents,
temperature, pH, and O2 in real-time, as a cabled observatory platform
for scientific research.
</p>
<h3><span id="Antarctic_FOCE_.28AntFOCE.29"></span><span class="mw-headline" id="Antarctic_FOCE_(AntFOCE)">Antarctic FOCE (AntFOCE)</span></h3>The
first polar FOCE (antFOCE) experiment was awarded funding in November
2012, followed by design and concept studies initiated in 2013.
Installation and initial science experiments are planned for 2014.
antFOCE is a collaborative effort between the University of Tasmania, <a href="https://en.wikipedia.org/wiki/Australian_Antarctic_Division" title="Australian Antarctic Division">Australian Antarctic Division</a>,
Antarctic Climate & Ecosystems Cooperative Research Centre,
Monterey Bay Aquarium Research Institute and specialist ocean
acidification policy advisors from the International Ocean Acidification
Reference Users Group (IOA-RUG). The IOA-RUG will take the lead in
communicating the outcomes of the FOCE experiment to global climate and
ocean policy related organizations.David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-31299036371105283792024-03-17T08:36:00.009-04:002024-03-17T08:36:50.456-04:00Indigenous response to colonialismFrom Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Indigenous_response_to_colonialism">https://en.wikipedia.org/wiki/Indigenous_response_to_colonialism</a><br /><div aria-labelledby="firstHeading" class="vector-body ve-init-mw-desktopArticleTarget-targetContainer" data-mw-ve-target-container="" id="bodyContent"><div class="vector-body-before-content">
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<div id="contentSub"><div id="mw-content-subtitle"></div></div>
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<p><b>Indigenous response to colonialism</b> has varied depending on the Indigenous group, historical period, territory, and colonial state(s) they have interacted with. <a href="https://en.wikipedia.org/wiki/Indigenous_peoples" title="Indigenous peoples">Indigenous peoples</a> have had <a href="https://en.wikipedia.org/wiki/Agency_(philosophy)" title="Agency (philosophy)">agency</a> in their response to <a href="https://en.wikipedia.org/wiki/Colonialism" title="Colonialism">colonialism</a>.
They have employed armed resistance, diplomacy, and legal procedures.
Others have fled to inhospitable, undesirable or remote territories to
avoid conflict. Nevertheless, some Indigenous peoples were forced to
move to <a href="https://en.wikipedia.org/wiki/Indian_reservation" title="Indian reservation">reservations</a> or <a href="https://en.wikipedia.org/wiki/Reductions" title="Reductions">reductions</a>, and <a href="https://en.wikipedia.org/wiki/Forced_labour" title="Forced labour">work</a> in mines, <a href="https://en.wikipedia.org/wiki/Plantation" title="Plantation">plantations</a>, construction, and domestic tasks. They have <a href="https://en.wikipedia.org/wiki/Detribalization" title="Detribalization">detribalized</a> and <a href="https://en.wikipedia.org/wiki/Cultural_assimilation" title="Cultural assimilation">culturally assimilated</a>
into colonial societies. On occasion, Indigenous peoples have formed
alliances with one or more Indigenous or non-Indigenous nations.
Overall, the response of Indigenous peoples to colonialism during this
period has been diverse and varied in its effectiveness. Indigenous resistance has a centuries-long history that is complex and carries on into contemporary times.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Council_at_Medicine_Lodge_Creek.png"><img class="mw-file-element" data-file-height="412" data-file-width="960" height="171" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Council_at_Medicine_Lodge_Creek.png/250px-Council_at_Medicine_Lodge_Creek.png" width="400" /></a><figcaption>The <a href="https://en.wikipedia.org/wiki/Kiowa" title="Kiowa">Kiowa</a>, <a href="https://en.wikipedia.org/wiki/Comanche" title="Comanche">Comanche</a>, <a href="https://en.wikipedia.org/wiki/Plains_Apache" title="Plains Apache">Plains Apache</a>, <a href="https://en.wikipedia.org/wiki/Cheyenne" title="Cheyenne">Cheyenne</a> and <a href="https://en.wikipedia.org/wiki/Arapaho" title="Arapaho">Arapaho</a> signed three successive treaties with the United States government, 1867.</figcaption></figure>
<h2><span class="mw-headline" id="Background">Background</span></h2></div></div></div><p><a href="https://en.wikipedia.org/wiki/Indigenous_peoples" title="Indigenous peoples">Indigenous peoples</a> are the earliest known inhabitants of a territory that was or remains <a href="https://en.wikipedia.org/wiki/Colonization" title="Colonization">colonized</a> by a dominant group. Before the age of <a href="https://en.wikipedia.org/wiki/Colonialism" title="Colonialism">colonialism</a>,
there were hundreds of nations and tribes throughout the territories
that would be colonized, with diverse languages, religions and cultures. The peoples that would come to be known as Indigenous had large cities, <a href="https://en.wikipedia.org/wiki/City-state" title="City-state">city-states</a>, <a href="https://en.wikipedia.org/wiki/Chiefdom" title="Chiefdom">chiefdoms</a>, states, kingdoms, republics, <a href="https://en.wikipedia.org/wiki/Confederation" title="Confederation">confederacies</a>,
and empires. These societies had varying degrees of knowledge of the
arts, agriculture, engineering, architecture, mathematics, astronomy,
writing, physics, medicine, irrigation, geology, mining, weather
forecasting, navigation, metallurgy and more. Their population would experience a significant <a href="https://en.wikipedia.org/wiki/Population_history_of_the_Indigenous_peoples_of_the_Americas" title="Population history of the Indigenous peoples of the Americas">collapse</a>
due to the effects of colonization. Most Indigenous groups in the world
today have been displaced from some or all of their ancestral <a href="https://en.wikipedia.org/wiki/Land_law" title="Land law">lands</a>.
Indigenous peoples have existed in a context of colonialism, as they
are not "Indigenous" without experiencing the practice of colonialism,
that is, when their sovereignty and self-determination are realized.
</p><p>In recent decades, non-Indigenous <a href="https://en.wikipedia.org/wiki/Historiography" title="Historiography">historiography</a> has paid increased attention to Indigenous <a href="https://en.wikipedia.org/wiki/Agency_(philosophy)" title="Agency (philosophy)">agency</a>.
Before, Indigenous peoples were studied as passive objects of colonial
policy and administration, but now the growing areas of <a href="https://en.wikipedia.org/wiki/Border" title="Border">borderland</a> studies and Indigenous agency have emerged.
</p><p>As European colonialism has spread throughout the world, settlers
have become dominant through conquest, occupation, or invasion. In this
process, there has been and continues to be conflict between settlers
and Indigenous peoples. For hundreds of years in recent history,
Indigenous groups have been the target of a number of atrocity crimes
including multiple <a href="https://en.wikipedia.org/wiki/Genocide_of_Indigenous_peoples" title="Genocide of Indigenous peoples">genocides</a>
that have destroyed entire nations. In spite of this, Indigenous
peoples survive and some are thriving. They account for a population of
476 million, residing in 90 countries around the world and speaking over
5000 languages from several <a href="https://en.wikipedia.org/wiki/Language_family" title="Language family">language families</a>, even though hundreds of Indigenous groups are extinct. Some examples of important surviving Indigenous languages include <a href="https://en.wikipedia.org/wiki/Aymara_people" title="Aymara people">Aymara</a>, <a href="https://en.wikipedia.org/wiki/Guaran%C3%AD_people" title="Guaraní people">Guaraní</a>, <a href="https://en.wikipedia.org/wiki/Quechua_people" title="Quechua people">Quechua</a> and <a href="https://en.wikipedia.org/wiki/Mapuche_language" title="Mapuche language">Mapuche</a> in South America; <a href="https://en.wikipedia.org/wiki/Lakota_people" title="Lakota people">Lakota</a> and <a href="https://en.wikipedia.org/wiki/Navajo" title="Navajo">Navajo</a> in North America; <a href="https://en.wikipedia.org/wiki/Maya_peoples" title="Maya peoples">Maya</a> and <a href="https://en.wikipedia.org/wiki/Nahuas" title="Nahuas">Nahua</a> in Central America; <a href="https://en.wikipedia.org/wiki/Inuit" title="Inuit">Inuit</a> in the circumpolar region; <a href="https://en.wikipedia.org/wiki/S%C3%A1mi_peoples" title="Sámi peoples">Sámi</a> in northwest Eurasia; and <a href="https://en.wikipedia.org/wiki/Torres_Strait_Islanders" title="Torres Strait Islanders">Torres Strait Islanders</a> and <a href="https://en.wikipedia.org/wiki/M%C4%81ori_people" title="Māori people">Māori</a> in <a href="https://en.wikipedia.org/wiki/Oceania" title="Oceania">Oceania.</a> For comparison, at the time of contact in <a href="https://en.wikipedia.org/wiki/1492" title="1492">1492</a>, there were 40 to 70 languages spoken in Europe, mostly from the <a href="https://en.wikipedia.org/wiki/Indo-European_languages" title="Indo-European languages">Indo-European</a> language family.
</p><p>Indigenous peoples continue to struggle as they suffer
discrimination in most countries where they coexist with non-Indigenous
peoples. The majority of the world's Indigenous peoples are among the
poorest groups within the states where they live, and they amount to 19%
of the world's poor.
</p>
<h2><span class="mw-headline" id="Contact_and_conquest">Contact and conquest</span></h2><figure class="mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Florentine_Codex_IX_Aztec_Warriors.jpg"><img class="mw-file-element" data-file-height="1020" data-file-width="2308" height="133" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Florentine_Codex_IX_Aztec_Warriors.jpg/300px-Florentine_Codex_IX_Aztec_Warriors.jpg" width="300" /></a><figcaption>Aztec warriors led by an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eagle_knight" title="Eagle knight">eagle knight</a>, each holding a <a href="https://en.wikipedia.org/wiki/Macuahuitl" title="Macuahuitl">macuahuitl</a> club. <a href="https://en.wikipedia.org/wiki/Florentine_Codex" title="Florentine Codex">Florentine Codex</a>, book IX, F, 5v. Manuscript written by <a href="https://en.wikipedia.org/wiki/Bernardino_de_Sahag%C3%BAn" title="Bernardino de Sahagún">Bernardino de Sahagún</a>.</figcaption></figure>
<p>Before Europeans set out to discover what had been populated by others in their <a href="https://en.wikipedia.org/wiki/Age_of_Discovery" title="Age of Discovery">Age of Discovery</a> and before the European <a href="https://en.wikipedia.org/wiki/History_of_colonialism" title="History of colonialism">colonization</a>,
Indigenous peoples resided in a large proportion of the world's
territory. For example, in the Americas, there are estimates of a <a href="https://en.wikipedia.org/wiki/Population_history_of_the_Indigenous_peoples_of_the_Americas" title="Population history of the Indigenous peoples of the Americas">population</a> of up to 100 million people. The Indigenous response to colonization has been varied and also
changed over time as each group chose to flee, fight, submit, support or
seek diplomatic solutions. One example of an Indigenous group that fled
is the <a href="https://en.wikipedia.org/wiki/Beothuk" title="Beothuk">Beothuk</a> in <a href="https://en.wikipedia.org/wiki/Newfoundland_(island)" title="Newfoundland (island)">Newfoundland</a>, which is now practically extinct. The <a href="https://en.wikipedia.org/wiki/Charr%C3%BAa" title="Charrúa">Charrúa</a> were <a href="https://en.wikipedia.org/wiki/Massacre_of_Salsipuedes" title="Massacre of Salsipuedes">massacred</a> in what is now <a href="https://en.wikipedia.org/wiki/Uruguay" title="Uruguay">Uruguay</a> and were completely destroyed. In contrast, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Nenets_people" title="Nenets people">Nenets</a> have accommodated the Russian state.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Malinche_con_Cortes.JPG"><img class="mw-file-element" data-file-height="726" data-file-width="1280" height="227" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Malinche_con_Cortes.JPG/250px-Malinche_con_Cortes.JPG" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/La_Malinche" title="La Malinche">Malinche</a> translating for <a href="https://en.wikipedia.org/wiki/Hern%C3%A1n_Cort%C3%A9s" title="Hernán Cortés">Hernán Cortés</a></figcaption></figure>
<p>For a long time, scholars have explained that the large fatality
rates of Indigenous peoples upon contact with settlers have been caused
by new infectious diseases brought to Indigenous territories from
overseas. Recent scholarship has shifted to explore the nature of the
difficult conditions of life imposed on Indigenous peoples due to
colonization itself, which made Indigenous peoples more vulnerable to
any disease, including new diseases. In other words, causes of death
such as forced labor combined with hunger that converged during the
colonization process made Indigenous peoples weaker and less resistant
to disease.
For example, scholars maintain that smallpox probably killed a third of
the population in colonial Mexico but admit that there is no evidence
to quantify the impact with certainty.
</p>
<figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Cuauhtl%C3%A1huac.jpg"><img class="mw-file-element" data-file-height="443" data-file-width="300" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Cuauhtl%C3%A1huac.jpg/220px-Cuauhtl%C3%A1huac.jpg" width="271" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Cuitl%C3%A1huac" title="Cuitláhuac">Cuitláhuac</a>, <a href="https://en.wikipedia.org/wiki/Aztecs" title="Aztecs">Aztec</a> <a href="https://en.wikipedia.org/wiki/Tlatoani" title="Tlatoani">Tlatoani</a> who led to victory in battle</figcaption></figure><p>
During the <a href="https://en.wikipedia.org/wiki/New_Spain" title="New Spain">colonization of New Spain</a>
from the 16th to the 18th centuries, the focus of the colonizers was to
practice agriculture, farming, mining, and infrastructure construction
while exploiting Indigenous labor. <a href="https://en.wikipedia.org/wiki/Slavery_in_colonial_Spanish_America" title="Slavery in colonial Spanish America">Slavery</a>
was one of the main factors that decimated the Indigenous population of
North America. Indigenous slavery predated and outlasted the <a href="https://en.wikipedia.org/wiki/Triangular_trade" title="Triangular trade">African slave trade</a> until the 20th century. The Spanish crown allowed slavery of Indigenous peoples captured in "<a href="https://en.wikipedia.org/wiki/Just_war_theory" title="Just war theory">just wars</a>", which included Indigenous resistance to colonialism, such as <a href="https://en.wikipedia.org/wiki/Religious_conversion" title="Religious conversion">religious conversion</a> or <a href="https://en.wikipedia.org/wiki/Forced_labour" title="Forced labour">forced labor</a>. Indigenous forced labor took place in <a href="https://en.wikipedia.org/wiki/Repartimiento" title="Repartimiento">repartimientos</a>, <a href="https://en.wikipedia.org/wiki/Encomienda" title="Encomienda">encomiendas</a>, <a href="https://en.wikipedia.org/wiki/Spanish_missions_in_California" title="Spanish missions in California">Spanish missions</a> and <a href="https://en.wikipedia.org/wiki/Hacienda" title="Hacienda">haciendas.</a> Indigenous women and children were forced to do domestic work. Even after slavery was outlawed by the <a href="https://en.wikipedia.org/wiki/Spanish_Empire" title="Spanish Empire">Spanish Empire</a>, and then ex-colonies such as the <a href="https://en.wikipedia.org/wiki/Mexico" title="Mexico">Mexican</a> and <a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a> governments, those that benefitted from <a href="https://en.wikipedia.org/wiki/Forced_labour" title="Forced labour">slavery</a> used legal frameworks to avoid enforcement such as <a href="https://en.wikipedia.org/wiki/Vagrancy" title="Vagrancy">vagrancy laws</a>, <a href="https://en.wikipedia.org/wiki/Convict_leasing" title="Convict leasing">convict leasing</a>, and <a href="https://en.wikipedia.org/wiki/Debt_bondage" title="Debt bondage">debt peonage</a>.</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Tenamaxtli_nochistlan.jpg"><img alt="" class="mw-file-element" data-file-height="250" data-file-width="167" height="400" src="https://upload.wikimedia.org/wikipedia/commons/7/7f/Tenamaxtli_nochistlan.jpg" width="267" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Francisco_Tenamaztle" title="Francisco Tenamaztle">Francisco Tenamaztle</a>, Indigenous leader in the <a href="https://en.wikipedia.org/wiki/Mixt%C3%B3n_War" title="Mixtón War">Mixtón War</a>, statue on the main square of <a href="https://en.wikipedia.org/wiki/Nochistl%C3%A1n_de_Mej%C3%ADa_Municipality" title="Nochistlán de Mejía Municipality">Nochistlán de Mejía</a>, <a href="https://en.wikipedia.org/wiki/Zacatecas" title="Zacatecas">Zacatecas</a></figcaption></figure>
<p>Indigenous nations sought diplomacy or military alliances to survive,
seeking allies in other nations, including neighbouring Indigenous
nations and other colonizing powers, as in the <a href="https://en.wikipedia.org/wiki/French_and_Indian_War" title="French and Indian War">French and Indian War</a> and the <a href="https://en.wikipedia.org/wiki/War_of_1812" title="War of 1812">War of 1812</a>. In Central America, <a href="https://en.wikipedia.org/wiki/Miskito_people" title="Miskito people">Miskito people</a> allied with the English to resist Spanish colonialism.
Indigenous peoples have sought alliances if the alliance has improved
their chances of survival or worked to their advantage. Some Indigenous
nations attempted to show their allegiance to the colonizing power by
becoming a military ally in the attacks of other Indigenous nations, as
in the case of the <a href="https://en.wikipedia.org/wiki/Tlaxcaltec" title="Tlaxcaltec">Tlaxcalans</a> in the central valley of Mexico. Other times, they would ally themselves with escaped African slaves, as in the case of the <a href="https://en.wikipedia.org/wiki/Seminole" title="Seminole">Seminoles</a>.
</p><p>On rare occasions, Indigenous peoples would be successful in battle against European armies. Examples include the <a href="https://en.wikipedia.org/wiki/Battle_of_Curalaba" title="Battle of Curalaba">Battle of Curalaba</a>, <a href="https://en.wikipedia.org/wiki/La_Noche_Triste" title="La Noche Triste">La Noche Triste</a>, <a href="https://en.wikipedia.org/wiki/Chichimeca_War" title="Chichimeca War">Chichimeca War</a> and the <a href="https://en.wikipedia.org/wiki/Battle_of_the_Little_Bighorn" title="Battle of the Little Bighorn">Battle of Big Horn</a>. The <a href="https://en.wikipedia.org/wiki/Mapuche" title="Mapuche">Mapuche</a> in Chile, the <a href="https://en.wikipedia.org/wiki/M%C4%81ori_people" title="Māori people">Māori</a> in New Zealand, the <a href="https://en.wikipedia.org/wiki/Yaqui" title="Yaqui">Yaquis</a> in Mexico, and the <a href="https://en.wikipedia.org/wiki/Seminole" title="Seminole">Seminoles</a> in Florida resisted for decades or even centuries.
However, in many parts of the world, Indigenous peoples moved away from
fertile, resource-rich territories to inaccessible and inhospitable
territories such as swamps, deserts and jungles.
They were displaced from fertile places in Argentina, Brazil, the
Philippines and temperate Africa. Some examples include small Indigenous
groups moving to parts of the Amazon basin, Australia, Central America,
the Arctic and Siberia. Others came into conflict with other Indigenous
groups as they were forcefully displaced and occupied territory that
was inhabited by other Indigenous groups.
On occasions, the reaction of Indigenous peoples to attacks resulted in their transformation into warrior <a href="https://en.wikipedia.org/wiki/Horse_culture" title="Horse culture">horse cultures</a>
that used European fire guns to resist further invasion of their
territories. Even today, the stereotypical Native American depicted in <a href="https://en.wikipedia.org/wiki/American_Indian_Wars" title="American Indian Wars">Indian Wars</a> is riding on a horse. For example, the people of the <a href="https://en.wikipedia.org/wiki/Great_Plains" title="Great Plains">Great Plains</a> and <a href="https://en.wikipedia.org/wiki/Mapuche" title="Mapuche">Mapuche</a> adopted the horse into their everyday cultures.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lautaro_y_Guacolda.jpg"><img class="mw-file-element" data-file-height="1208" data-file-width="1590" height="304" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Lautaro_y_Guacolda.jpg/220px-Lautaro_y_Guacolda.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Lautaro" title="Lautaro">Lautaro</a> and <a href="https://en.wikipedia.org/wiki/Guacolda_(Mapuche)" title="Guacolda (Mapuche)">Guacolda</a></figcaption></figure>
<p>Indigenous peoples also adopted newly introduced domestic animals in
their diet as Europeans introduced chicken, cattle, pigs, goats, and
sheep in the <a href="https://en.wikipedia.org/wiki/Columbian_exchange" title="Columbian exchange">Columbian exchange</a>.
Indigenous peoples have hunted their territory for centuries or
millennia, and many times killed the animals belonging to settlers, and
this has been the cause of much conflict between settlers and Indigenous
peoples.</p><p>Indigenous peoples were not always conquered militarily, as in the case of <a href="https://en.wikipedia.org/wiki/Treaty" title="Treaty">treaties</a> made between Great Britain and France with Indigenous peoples. The 1840 <a href="https://en.wikipedia.org/wiki/Treaty_of_Waitangi" title="Treaty of Waitangi">Treaty of Waitangi</a> of the Maori, and the 1868 <a href="https://en.wikipedia.org/wiki/Treaty_of_Bosque_Redondo" title="Treaty of Bosque Redondo">Treaty of Bosque Redondo</a> of the <a href="https://en.wikipedia.org/wiki/Navajo_Nation" title="Navajo Nation">Navajo</a> are two examples of treaties that remain important today.
</p>
<h2><span class="mw-headline" id="Colonization">Colonization</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Felipe_Guam%C3%A1n_Poma_de_Ayala.jpg"><img class="mw-file-element" data-file-height="574" data-file-width="400" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Felipe_Guam%C3%A1n_Poma_de_Ayala.jpg/220px-Felipe_Guam%C3%A1n_Poma_de_Ayala.jpg" width="278" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Felipe_Guaman_Poma_de_Ayala" title="Felipe Guaman Poma de Ayala">Felipe Guaman Poma de Ayala</a></figcaption></figure>
<p>Modern colonialism that started in the 15th century, along with European <a href="https://en.wikipedia.org/wiki/Triangular_trade" title="Triangular trade">transatlantic</a>
navigation, resulted in the expansion of European empires and the
associated settler colonialism that occurred in the Americas, Oceania,
South Africa and beyond.
</p><p>According to historian <a href="https://en.wikipedia.org/wiki/Roxanne_Dunbar-Ortiz" title="Roxanne Dunbar-Ortiz">Roxanne Dunbar-Ortiz</a>, the fact that Indigenous peoples survive today against genocidal attacks is proof of resistance:
</p>
<blockquote class="templatequote"><p>Native nations and communities,
while struggling to maintain fundamental values and collectivity, have
from the beginning resisted modern colonialism
using both defensive and offensive techniques, including the modern
forms of armed resistance of national liberation movements and what now
is called terrorism. In every instance they have fought for survival as
peoples.</p></blockquote>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Liropeya.jpg"><img class="mw-file-element" data-file-height="486" data-file-width="565" height="344" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Liropeya.jpg/220px-Liropeya.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Charr%C3%BAa" title="Charrúa">Charrua</a> and soldier.</figcaption></figure>
<p>Dunbar-Ortiz sets examples of resistance in North America in the cases of the <a href="https://en.wikipedia.org/wiki/Pueblo_Revolt" title="Pueblo Revolt">Pueblo Revolt</a>, the <a href="https://en.wikipedia.org/wiki/Pequot_War" title="Pequot War">Pequot War</a>, <a href="https://en.wikipedia.org/wiki/King_Philip%27s_War" title="King Philip's War">King Philip's War</a>, and the <a href="https://en.wikipedia.org/wiki/Seminole_Wars" title="Seminole Wars">Seminole Wars</a>.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Geronimo_(Goyathlay),_a_Chiricahua_Apache,_full-length,_kneeling_with_rifle,_1887_-_NARA_-_530880.jpg"><img class="mw-file-element" data-file-height="2406" data-file-width="1835" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/58/Geronimo_%28Goyathlay%29%2C_a_Chiricahua_Apache%2C_full-length%2C_kneeling_with_rifle%2C_1887_-_NARA_-_530880.jpg/220px-Geronimo_%28Goyathlay%29%2C_a_Chiricahua_Apache%2C_full-length%2C_kneeling_with_rifle%2C_1887_-_NARA_-_530880.jpg" width="306" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Geronimo" title="Geronimo">Geronimo</a>, <a href="https://en.wikipedia.org/wiki/Apache" title="Apache">Apache</a> leader</figcaption></figure>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Estatua_de_Lempira.jpg"><img class="mw-file-element" data-file-height="1008" data-file-width="477" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Estatua_de_Lempira.jpg/100px-Estatua_de_Lempira.jpg" width="190" /></a><figcaption>Statue of Lempira, Plaza Central de Tambla</figcaption></figure>
<p>Historical Indigenous resistance leaders throughout the world include <a href="https://en.wikipedia.org/wiki/Cajem%C3%A9" title="Cajemé">Cajemé</a>, <a href="https://en.wikipedia.org/wiki/Caupolic%C3%A1n" title="Caupolicán">Caupolican</a>, <a href="https://en.wikipedia.org/wiki/Dundalli" title="Dundalli">Dundalli</a>, <a href="https://en.wikipedia.org/wiki/Geronimo" title="Geronimo">Geronimo</a>, <a href="https://en.wikipedia.org/wiki/Lautaro" title="Lautaro">Lautaro</a>, <a href="https://en.wikipedia.org/wiki/Lempira_(Lenca_ruler)" title="Lempira (Lenca ruler)">Lempira</a>, <a href="https://en.wikipedia.org/wiki/Mangas_Coloradas" title="Mangas Coloradas">Mangas Coloradas</a>, <a href="https://en.wikipedia.org/wiki/Manco_Inca_Yupanqui" title="Manco Inca Yupanqui">Manco Inca</a>, <a href="https://en.wikipedia.org/wiki/T%C3%BApac_Amaru_II" title="Túpac Amaru II">Tupac Amaru II</a>, <a href="https://en.wikipedia.org/wiki/Tecumseh" title="Tecumseh">Tecumseh</a>, and <a href="https://en.wikipedia.org/wiki/Tenskwatawa" title="Tenskwatawa">Tenskwatawa</a>.
</p><p>
At times, Indigenous peoples used violent resistance, at times
successfully or at times involving two or more Indigenous allies.
Examples include the <a href="https://en.wikipedia.org/wiki/Mixt%C3%B3n_War" title="Mixtón War">Mixton rebellion</a>, the <a href="https://en.wikipedia.org/wiki/Zapatista_uprising" title="Zapatista uprising">Zapatista uprising</a>, the <a href="https://en.wikipedia.org/wiki/Caste_War_of_Yucat%C3%A1n" title="Caste War of Yucatán">Caste War of Yucatán</a>, <a href="https://en.wikipedia.org/wiki/Rebellion_of_T%C3%BApac_Amaru_II" title="Rebellion of Túpac Amaru II">Rebellion of Tupac Amaru II</a>, the <a href="https://en.wikipedia.org/wiki/Tzeltal_Rebellion_of_1712" title="Tzeltal Rebellion of 1712">Tzeltal Rebellion of 1712</a>, <a href="https://en.wikipedia.org/wiki/Pontiac%27s_War" title="Pontiac's War">Pontiac's War</a> and the <a href="https://en.wikipedia.org/wiki/North-West_Rebellion" title="North-West Rebellion">North-West Rebellion</a>. Academic Benjamin Madley said that throughout the world, groups
targeted for annihilation resist, often violently. He details the case
of the <a href="https://en.wikipedia.org/wiki/Modoc_War" title="Modoc War">Modoc War</a>
comparing the casualties of the conflict. Furthermore, he says that
"The Modoc genocide is hardly the only genocide against Indigenous
people that has been sanitized as war."
According to Frank Chalk, in the 19th century United States, the
federal government policy toward Native Americans was ethnocide, but
when they resisted, the result sometimes was genocidal. Historically, victims of genocide have resisted, and this resistance has been criminalized to justify massacres.</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Colorized_Version_of_Powhatan_Attack_of_1622.jpg"><img class="mw-file-element" data-file-height="717" data-file-width="900" height="318" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/01/Colorized_Version_of_Powhatan_Attack_of_1622.jpg/220px-Colorized_Version_of_Powhatan_Attack_of_1622.jpg" width="400" /></a><figcaption>1622 <a href="https://en.wikipedia.org/wiki/Indian_massacre_of_1622" title="Indian massacre of 1622">Jamestown massacre</a>. The image is largely considered conjecture.</figcaption></figure><p>
According to Ken Coates, sexual relations between Indigenous women and
non-Indigenous men took place to some extent in New Zealand, <a href="https://en.wikipedia.org/wiki/New_Spain" title="New Spain">New Spain</a>, the <a href="https://en.wikipedia.org/wiki/M%C3%A9tis" title="Métis">Metis</a>
in Canada, whereas they generally did not take place in other places
such as Australia and British North America. People of mixed
settler-Indigenous ancestry have been discriminated against. The mixing
blurred the lines between Indigenous and newcomer populations, and most
learned the language of the colony, which was a European language. Some scholars have argued that the concept of <a href="https://en.wikipedia.org/wiki/Mestizo" title="Mestizo">mestizaje</a>, the process of <a href="https://en.wikipedia.org/wiki/Transculturation" title="Transculturation">transcultural</a> mixing, has been used to promote assimitionalism and monoculturalism in Latin America.</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Maori_soldiers_performing_a_Haka_dance_at_Avondale_Camp_1915.jpg"><img class="mw-file-element" data-file-height="490" data-file-width="992" height="198" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Maori_soldiers_performing_a_Haka_dance_at_Avondale_Camp_1915.jpg/220px-Maori_soldiers_performing_a_Haka_dance_at_Avondale_Camp_1915.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/M%C4%81ori_people" title="Māori people">Maori</a> soldiers, 1915</figcaption></figure>
<p>In North America, where the British made <a href="https://en.wikipedia.org/wiki/Treaty_rights" title="Treaty rights">treaties</a> with Indigenous peoples, they learned that these treaties could be broken and would not protect their communities. Faced with the risk that their people would be destroyed, leaders of Indian resistance agreed to <a href="https://en.wikipedia.org/wiki/Treaty_rights" title="Treaty rights">treaties</a> requiring land <a href="https://en.wikipedia.org/wiki/Cession" title="Cession">cessions</a>, and the redefinition of borders in the hope that the settlers would not encroach further on Indigenous territory. One of such examples is the <a href="https://en.wikipedia.org/wiki/Pokagon_Band_of_Potawatomi_Indians" title="Pokagon Band of Potawatomi Indians">Pokagon Band of Potawatomi Indians</a>, a federally recognized Indian Nation, which was led by <a href="https://en.wikipedia.org/wiki/Potawatomi" title="Potawatomi">Potawatomi</a> leader <a href="https://en.wikipedia.org/wiki/Leopold_Pokagon" title="Leopold Pokagon">Leopold Pokagon</a>. Other times, treaties were signed under <a href="https://en.wikipedia.org/wiki/Coercion" title="Coercion">coercion</a> or right after Indigenous groups suffered massacres, such as in the case of the <a href="https://en.wikipedia.org/wiki/Treaty_of_Hartford_(1638)" title="Treaty of Hartford (1638)">Treaty of Hartford</a> of 1638. Colonial powers also sought control of new territories by appropriating the Indigenous elite through <a href="https://en.wikipedia.org/wiki/Bribery" title="Bribery">bribery</a> and <a href="https://en.wikipedia.org/wiki/Cultural_assimilation_of_Native_Americans" title="Cultural assimilation of Native Americans">assimilation</a>.
</p><p>In North America, the <a href="https://en.wikipedia.org/wiki/American_Indian_boarding_schools" title="American Indian boarding schools">United States</a> and Canada established <a href="https://en.wikipedia.org/wiki/Canadian_Indian_residential_school_system" title="Canadian Indian residential school system">residential schools</a>,
removing Indigenous children from their families for years while
prohibiting the use of their Indigenous language and cultural practices.
Australia focused on children with <a href="https://en.wikipedia.org/wiki/Multiracial_people" title="Multiracial people">mixed ethnicity</a> and removed children to be placed in residential schools or to be <a href="https://en.wikipedia.org/wiki/Adoption" title="Adoption">adopted</a> by non-Indigenous families. Canada and the United States have assimilated Indigenous peoples via <a href="https://en.wikipedia.org/wiki/Indian_termination_policy" title="Indian termination policy">Indian termination policies</a>,
in which incentives are offered for Indigenous peoples to renounce
Indigenous rights in exchange for benefits such as citizenship rights.
Furthermore, Canada removed Indigenous rights if an Indigenous woman
married a non-Indigenous person, an Indigenous person graduated from
university, or joined the military.
</p><p>The <a href="https://en.wikipedia.org/wiki/Cherokee_Nation" title="Cherokee Nation">Cherokee Nation</a> is one of the <a href="https://en.wikipedia.org/wiki/List_of_federally_recognized_tribes_in_the_contiguous_United_States" title="List of federally recognized tribes in the contiguous United States">federally recognized tribes within the United States</a>. It is now located in <a href="https://en.wikipedia.org/wiki/Oklahoma" title="Oklahoma">Oklahoma</a> after being forcefully removed in the <a href="https://en.wikipedia.org/wiki/Trail_of_Tears" title="Trail of Tears">Trail of Tears</a>
along with other Indigenous groups. Indigenous groups in North America
were assigned to small reservations, typically on remote and
economically marginal territories that would not support crops, fishing
or hunting. Some of the reservations were then dismantled through an
allotment process such as the <a href="https://en.wikipedia.org/wiki/Dawes_Act" title="Dawes Act">Dawes act</a> in North America, but some Indigenous peoples refused to sign.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Cree_Indian_sun_dancers,_probably_Montana,_ca_1893_(LAROCHE_126).jpeg"><img class="mw-file-element" data-file-height="500" data-file-width="835" height="240" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Cree_Indian_sun_dancers%2C_probably_Montana%2C_ca_1893_%28LAROCHE_126%29.jpeg/220px-Cree_Indian_sun_dancers%2C_probably_Montana%2C_ca_1893_%28LAROCHE_126%29.jpeg" width="400" /></a><figcaption>Cree Indian <a href="https://en.wikipedia.org/wiki/Sun_Dance" title="Sun Dance">sun dancers</a>, ca 1893</figcaption></figure>
<p>A 2009 United Nations report stated that Indigenous peoples have
"...documented histories of resistance, interface or cooperation with
states...Indigenous peoples were often recognized as sovereign peoples
by states, as witnessed by the hundreds of treaties concluded between
Indigenous peoples and the governments of the United States, Canada, New
Zealand and others".
</p>
<h2><span class="mw-headline" id="Contemporary_response">Contemporary response</span></h2><h3><span class="mw-headline" id="Strategies">Strategies</span></h3><p>Indigenous strategies continue to pursue <a href="https://en.wikipedia.org/wiki/Indigenous_rights" title="Indigenous rights">Indigenous rights</a>
and freedom and seek to rebuild their nations and cultures to maintain
national groups with distinct cultural identities. Indigenous nations
continue to pursue <a href="https://en.wikipedia.org/wiki/Self-determination" title="Self-determination">self-determination</a> and <a href="https://en.wikipedia.org/wiki/Sovereignty" title="Sovereignty">sovereignty</a>.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Derribo_de_la_estatua_de_Diego_de_Mazariegos.jpg"><img class="mw-file-element" data-file-height="562" data-file-width="371" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Derribo_de_la_estatua_de_Diego_de_Mazariegos.jpg/220px-Derribo_de_la_estatua_de_Diego_de_Mazariegos.jpg" width="264" /></a><figcaption>Protesters toppled a statue of <a href="https://en.wikipedia.org/wiki/Diego_de_Mazariegos" title="Diego de Mazariegos">Diego de Mazariegos</a>, a Spanish <i><a href="https://en.wikipedia.org/wiki/Conquistador" title="Conquistador">conquistador</a></i>. 1992.</figcaption></figure>
<p>Contemporary Indigenous strategies have included negotiations,
mediation, arbitration, political statements, blockades, legal
challenges, <a href="https://en.wikipedia.org/wiki/Activism" title="Activism">activism</a>, <a href="https://en.wikipedia.org/wiki/Political_demonstration" title="Political demonstration">political demonstrations</a> and <a href="https://en.wikipedia.org/wiki/Civil_disobedience" title="Civil disobedience">civil disobedience</a>. A few have worked on the removal from public spaces of symbols of Indigenous oppression, such as <a href="https://en.wikipedia.org/wiki/Monument" title="Monument">monuments</a> to <a href="https://en.wikipedia.org/wiki/Christopher_Columbus" title="Christopher Columbus">Christopher Columbus</a>, <a href="https://en.wikipedia.org/wiki/John_A._Macdonald" title="John A. Macdonald">John A. Macdonald</a>, and <a href="https://en.wikipedia.org/wiki/Jun%C3%ADpero_Serra" title="Junípero Serra">Junipero Serra</a>. Much resistance has also been used to bring Indigenous issues to public attention.
</p><p>Indigenous peoples commemorate historical events and processes on an annual or periodic basis. Examples include <a href="https://en.wikipedia.org/wiki/Unthanksgiving_Day" title="Unthanksgiving Day">Unthanksgiving Day</a> and <a href="https://en.wikipedia.org/wiki/Indigenous_Peoples%27_Day_(United_States)" title="Indigenous Peoples' Day (United States)">Indigenous Peoples Day</a>. Activists have also protested what they consider controversial colonial holidays, such as <a href="https://en.wikipedia.org/wiki/Australia_Day" title="Australia Day">Australia Day</a>, and <a href="https://en.wikipedia.org/wiki/Columbus_Day" title="Columbus Day">Columbus Day</a> and its <a href="https://en.wikipedia.org/wiki/Columbus_Quincentenary" title="Columbus Quincentenary">quincentenary</a> celebration.
</p><p>Erich Steinman has compiled a record of Native American
resistance processes and responses that he says are not well studied by
American sociology.
</p><p>In New Zealand and Ecuador, Indigenous peoples have formed political parties, <a href="https://en.wikipedia.org/wiki/Te_P%C4%81ti_M%C4%81ori" title="Te Pāti Māori">Te Pāti Māori</a> and <a href="https://en.wikipedia.org/wiki/Pachakutik_Plurinational_Unity_Movement_%E2%80%93_New_Country" title="Pachakutik Plurinational Unity Movement – New Country">Pachakutik</a> respectively. Bolivia has had an Indigenous president, <a href="https://en.wikipedia.org/wiki/Evo_Morales" title="Evo Morales">Evo Morales</a>.
</p><p>Indigenous nations and peoples have managed to survive despite sustained long-term attacks to their <a href="https://en.wikipedia.org/wiki/Survival" title="Survival">survival</a> as Indigenous nations, cultures or as members of an Indigenous group. Hall argues that Indigenous peoples challenge the idea that the <a href="https://en.wikipedia.org/wiki/State_(polity)" title="State (polity)">state</a>
is the basic form of political organization. He argues that the
Indigenous fight for self-determination today is part of a cycle of
centuries of resistance to colonialism.
</p>
<h3><span class="mw-headline" id="Views_on_ongoing_colonialism">Views on ongoing colonialism</span></h3><p>Elaine Coburn and historian <a href="https://en.wikipedia.org/wiki/Lorenzo_Veracini" title="Lorenzo Veracini">Lorenzo Veracini</a> say that colonialism is present in contemporary settler colonial states, including <a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a>, <a href="https://en.wikipedia.org/wiki/New_Zealand" title="New Zealand">New Zealand</a>, <a href="https://en.wikipedia.org/wiki/Australia" title="Australia">Australia</a>, and the <a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a>.
Michael Grewcock has argued that in Australia, there are Indigenous
peoples "who still resist the colonization of country that was never
ceded".
</p><p>Native American anthropologist <a href="https://en.wikipedia.org/wiki/Audra_Simpson" title="Audra Simpson">Audra Simpson</a> argues that the colonial project is ongoing, as the case of the Mohawks of <a href="https://en.wikipedia.org/wiki/Kahnawake" title="Kahnawake">Kahnawake</a>, a self-governing territory of the <a href="https://en.wikipedia.org/wiki/Mohawk_people" title="Mohawk people">Mohawk Nation</a> within the borders of Canada.
</p><p>Pablo G. Casanova has said that in Mexico there has been a practice of <a href="https://en.wikipedia.org/wiki/Internal_colonialism" title="Internal colonialism">internal colonialism</a>. According to sociologist <a href="https://en.wikipedia.org/wiki/An%C3%ADbal_Quijano" title="Aníbal Quijano">Anibal Quijano</a>, Bolivia and Mexico have undergone limited <a href="https://en.wikipedia.org/wiki/Decolonization" title="Decolonization">decolonialization</a> through a revolutionary process. In Mexico, the case of the <a href="https://en.wikipedia.org/wiki/Zapatista_Army_of_National_Liberation" title="Zapatista Army of National Liberation">Ejercito Zapatista de Liberación Nacional</a>
(EZLN) denotes resistance in many areas, including education,
territorial, epistemological, political and economic terms. EZLN is
viewed as a continuation of the struggle against more than 500 years of
oppression of Indigenous peoples.
</p><p>According to Ken Coates, liberal democracies do not like being
called up on internal human rights abuses "when these same governments
are often prominent in criticizing other nations for abuses of human and
civil rights". Furthermore, post-independence era countries such as
Malaysia and Indonesia have been dismissive of Indigenous rights as much
as colonial empires.
</p>
<h3><span class="mw-headline" id="Indigenous_storytelling">Indigenous storytelling</span></h3><p><a href="https://en.wikipedia.org/wiki/Oral_storytelling" title="Oral storytelling">Oral storytelling</a> is important to Indigenous culture, but it has been underepresented. <a href="https://en.wikipedia.org/wiki/Roxanne_Dunbar-Ortiz" title="Roxanne Dunbar-Ortiz">Roxanne Dunbar-Ortiz</a> has said that when <a href="https://en.wikipedia.org/wiki/Howard_Zinn" title="Howard Zinn">Howard Zinn</a>
wrote his United States' history book, he did not include the history
of the Indigenous peoples, so he said that she could write what would
become such a book: <i><a href="https://en.wikipedia.org/wiki/An_Indigenous_Peoples%27_History_of_the_United_States" title="An Indigenous Peoples' History of the United States">An Indigenous Peoples' History of the United States</a></i>. <a href="https://en.wikipedia.org/wiki/Rigoberta_Mench%C3%BA" title="Rigoberta Menchú">Rigoberta Menchu</a> published an essay about her life with personal experiences directly related to the <a href="https://en.wikipedia.org/wiki/Guatemalan_genocide" title="Guatemalan genocide">Guatemalan genocide</a> and went on to win the <a href="https://en.wikipedia.org/wiki/Nobel_Peace_Prize" title="Nobel Peace Prize">Nobel Peace Prize</a>.
</p>
<h3><span class="mw-headline" id="Truth_commissions">Truth commissions</span></h3><p>There are <a href="https://en.wikipedia.org/wiki/Truth_commission" title="Truth commission">Truth Commissions</a> that have investigated and reported on Indigenous atrocities. Some of them include the <a href="https://en.wikipedia.org/wiki/Historical_Clarification_Commission" title="Historical Clarification Commission">Guatemala Historical Clarification Commission</a>, the <a href="https://en.wikipedia.org/wiki/Truth_and_Reconciliation_Commission_of_Canada" title="Truth and Reconciliation Commission of Canada">Truth and Reconciliation Commission</a> of Canada, and the <a href="https://en.wikipedia.org/wiki/Truth_and_Reconciliation_Commission_(Norway)" title="Truth and Reconciliation Commission (Norway)">Truth and Reconciliation Commission of Norway</a>.
</p>
<h3><span class="mw-headline" id="Museums">Museums</span></h3><p>In Latin America, there are only a few museums whose central theme is that of colonization and history of Indigenous peoples.
</p><p>Indigenous peoples and others have protested against museum´s exhibitions. Notable examples of Indigenous museums are <a href="https://en.wikipedia.org/wiki/Museu_do_%C3%8Dndio" title="Museu do Índio">Museu do Índio</a> (Rio de Janeiro, Brasil), <a href="https://en.wikipedia.org/wiki/Royal_Museum_for_Central_Africa" title="Royal Museum for Central Africa">Royal Museum for Central Africa</a> (Brussels, Belgium), <a href="https://en.wikipedia.org/wiki/Mus%C3%A9e_du_Quai_Branly_%E2%80%93_Jacques_Chirac" title="Musée du Quai Branly – Jacques Chirac">Musée du Quai Branly</a> (Paris, France), <a href="https://en.wikipedia.org/wiki/National_Museum_of_Anthropology_(Mexico)" title="National Museum of Anthropology (Mexico)">National Museum of Anthropology</a> (Mexico City), <a href="https://en.wikipedia.org/wiki/Wereldmuseum_Amsterdam" title="Wereldmuseum Amsterdam">Museum of the Tropics</a> (Amsterdam, Netherlands), <a href="https://en.wikipedia.org/wiki/Museo_Nacional_de_Antropolog%C3%ADa_(Madrid)" title="Museo Nacional de Antropología (Madrid)">Museo Nacional de Antropología</a> and <a href="https://en.wikipedia.org/wiki/Museo_de_Am%C3%A9rica" title="Museo de América">Museo de América</a> (Madrid, Spain), <a href="https://en.wikipedia.org/wiki/American_Indian_Genocide_Museum" title="American Indian Genocide Museum">American Indian Genocide Museum</a> (Houston, USA), <a href="https://en.wikipedia.org/wiki/George_Gustav_Heye_Center" title="George Gustav Heye Center">George Gustav Heye Center</a> (New York City, USA), and <a href="https://en.wikipedia.org/wiki/National_Museum_of_the_American_Indian" title="National Museum of the American Indian">National Museum of the American Indian</a> (Washington, D.C., USA).
</p><p>Many smaller European colonial museums have closed after the end of European colonization.
According to Pascal Blanchard, the political climate in France has not
allowed the emergence of a museum about French colonialism. In <a href="https://en.wikipedia.org/wiki/Bristol" title="Bristol">Bristol</a>, England, the only museum dedicated to colonialism, <a href="https://en.wikipedia.org/wiki/British_Empire_and_Commonwealth_Museum" title="British Empire and Commonwealth Museum">British Empire and Commonwealth Museum</a>, has been closed after operating for just 6 years.
</p><p>In North America, <a href="https://en.wikipedia.org/wiki/American_Museum_of_Natural_History" title="American Museum of Natural History">American Museum of Natural History</a> in New York, Chicago’s <a href="https://en.wikipedia.org/wiki/Field_Museum_of_Natural_History" title="Field Museum of Natural History">Field Museum of Natural History</a>, Harvard University’s <a href="https://en.wikipedia.org/wiki/Peabody_Museum_of_Archaeology_and_Ethnology" title="Peabody Museum of Archaeology and Ethnology">Peabody Museum of Archaeology and Ethnology</a> and <a href="https://en.wikipedia.org/wiki/Cleveland_Museum_of_Art" title="Cleveland Museum of Art">Cleveland Museum of Art</a>
have begun to close exhibits with Indigenous themes to comply with
federal regulations that mandate tribal consent and repatriation of
human remains.
</p>
<h3><span class="mw-headline" id="Indigenous_media">Indigenous media</span></h3><p>There are a number of Indigenous broadcasting organizations from countries serving <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Indigenous_people" title="Indigenous people">Indigenous</a> themes, including <a href="https://en.wikipedia.org/wiki/APTN_National_News" title="APTN National News">APTN</a>, <a href="https://en.wikipedia.org/wiki/First_Nations_Experience" title="First Nations Experience">First Nations Experience</a>, <a href="https://en.wikipedia.org/wiki/National_Indigenous_Television" title="National Indigenous Television">NITV</a>, <a href="https://en.wikipedia.org/wiki/NRK_S%C3%A1pmi" title="NRK Sápmi">NRK Sami</a> and <a href="https://en.wikipedia.org/wiki/Whakaata_M%C4%81ori" title="Whakaata Māori">Whakaata Māori</a>.
</p>
<h3><span class="mw-headline" id="Language">Language</span></h3><p>Some movements, such as the <a href="https://en.wikipedia.org/wiki/Hawaiian_sovereignty_movement" title="Hawaiian sovereignty movement">Hawaiian sovereignty movement</a>, have sought to promote the use of Indigenous languages in educational programs. In recent years, there has been a revival in the use of <a href="https://en.wikipedia.org/wiki/M%C4%81ori_language" title="Māori language">Māori</a> language in New Zealand, where it is an official language and taught in 350 schools. New technologies are making access to educational language programs accessible to the general public.
Furthermore, there are examples of Indigenous schools that move away
from Eurocentric curriculums while considering the graduates' future
prospects within a non-Indigenous majority state. In <a href="https://en.wikipedia.org/wiki/Paraguay" title="Paraguay">Paraguay</a>, <a href="https://en.wikipedia.org/wiki/Guarani_language" title="Guarani language">Guaraní</a> is the <a href="https://en.wikipedia.org/wiki/Official_language" title="Official language">official language</a> and is spoken by 6.5 million people in the region. <a href="https://en.wikipedia.org/wiki/Quechuan_languages" title="Quechuan languages">Quechua</a> and <a href="https://en.wikipedia.org/wiki/Aymara_language" title="Aymara language">Aymara</a> are official languages in Peru and Bolivia and are spoken by 8 and 2.5 million people, respectively.
Nationalism has promoted the use of local languages in most of Eurasia,
but in the rest of the world, European languages remain dominant in
mass media, education and the internet.
</p>
<h3><span class="mw-headline" id="Culture">Culture</span></h3><p>Today, Indigenous peoples can react to <a href="https://en.wikipedia.org/wiki/Culture" title="Culture">cultural</a> processes in various ways, including <a href="https://en.wikipedia.org/wiki/Acculturation" title="Acculturation">acculturation</a>, <a href="https://en.wikipedia.org/wiki/Transculturation" title="Transculturation">transculturation</a>, <a href="https://en.wikipedia.org/wiki/Cultural_assimilation_of_Native_Americans" title="Cultural assimilation of Native Americans">assimilation</a>,
and cultural loss, while some remain separated from the dominant
culture or marginalized from any group, including their own. In <a href="https://en.wikipedia.org/wiki/Hispanic_America" title="Hispanic America">Hispanic America</a>, Indigenous peoples have adopted Spanish religion, institutions, language, and literature, as well as non-<a href="https://en.wikipedia.org/wiki/Endemism" title="Endemism">endemic</a> domestic animals and crops.
</p><p>Some scholars and Indigenous peoples argue that renaming
geographical entities should be part of a reclaiming process of
Indigenous cultures.
</p>
<h3><span class="mw-headline" id="International_law">International law</span></h3><p>In the area of international law, the <a href="https://en.wikipedia.org/wiki/Working_Group_on_Indigenous_Populations" title="Working Group on Indigenous Populations">Working Group on Indigenous Populations</a> participated directly in the development of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/United_Nations_Declaration_on_the_Rights_of_Indigenous_Peoples" title="United Nations Declaration on the Rights of Indigenous Peoples">United Nations Declaration on the Rights of Indigenous Peoples</a> (UNDRIP) and worked on the development of the <a href="https://en.wikipedia.org/wiki/Indigenous_and_Tribal_Peoples_Convention,_1989" title="Indigenous and Tribal Peoples Convention, 1989">Indigenous and Tribal Peoples Convention</a> of 1989.
Indigenous scholar Jeff Corntassel said that article 46 of UNDRIP may
be detrimental to some Indigenous rights: "...the restoration of their
land-based and water-based cultural relationships and practices is often
portrayed as a threat to the territorial integrity of the country(ies)
in which they reside, and thus, a threat to state sovereignty".
</p><p>For decades, Indigenous peoples had demanded that the Catholic Church rescinded the <a href="https://en.wikipedia.org/wiki/Discovery_doctrine" title="Discovery doctrine">Doctrine of Discovery</a> theories that justified the seizure of Indigenous land and supported a legal basis.<sup class="reference" id="cite_ref-145"><a href="https://en.wikipedia.org/wiki/Indigenous_response_to_colonialism#cite_note-145"></a></sup></p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-16420358243881602612024-03-17T08:10:00.002-04:002024-03-17T08:10:16.066-04:00Colonialism and genocide<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Colonialism_and_genocide">https://en.wikipedia.org/wiki/Colonialism_and_genocide</a> </div>
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<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Gedenkstein_Columbiadamm_122_(Neuk)_Opfer_der_Kolonialherrschaft.jpg"><img class="mw-file-element" data-file-height="1266" data-file-width="996" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Gedenkstein_Columbiadamm_122_%28Neuk%29_Opfer_der_Kolonialherrschaft.jpg/220px-Gedenkstein_Columbiadamm_122_%28Neuk%29_Opfer_der_Kolonialherrschaft.jpg" width="314" /></a><figcaption>Memorial in <a href="https://en.wikipedia.org/wiki/Neuk%C3%B6lln_(locality)" title="Neukölln (locality)">Berlin-Neukölln</a> to the Victims of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Herero_and_Namaqua_genocide" title="Herero and Namaqua genocide">Herero and Namaqua genocide</a> perpetrated by the <a href="https://en.wikipedia.org/wiki/German_Empire" title="German Empire">German Empire</a> against the <a href="https://en.wikipedia.org/wiki/Herero_people" title="Herero people">Herero</a> and <a href="https://en.wikipedia.org/wiki/Nama_people" title="Nama people">Nama peoples</a> of Namibia</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Tibet_genocide.jpg"><img class="mw-file-element" data-file-height="1998" data-file-width="1464" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Tibet_genocide.jpg/220px-Tibet_genocide.jpg" width="293" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Tibetan_people" title="Tibetan people">Tibetan people</a> in protest against their treatment by China</figcaption></figure>
<p>The connection between <b><a href="https://en.wikipedia.org/wiki/Colonialism" title="Colonialism">colonialism</a> and <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a></b> has been explored in academic research. According to historian <a href="https://en.wikipedia.org/wiki/Patrick_Wolfe" title="Patrick Wolfe">Patrick Wolfe</a>, "[t]he question of genocide is never far from discussions of <a href="https://en.wikipedia.org/wiki/Settler_colonialism" title="Settler colonialism">settler colonialism</a>." Historians have commented that although <a href="https://en.wikipedia.org/wiki/Colonialism" title="Colonialism">colonialism</a> does not necessarily directly involve <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>, research suggests that the two share a connection.
</p><p>Colonialism has been reinforced during various periods in <a href="https://en.wikipedia.org/wiki/History" title="History">history</a>, even during progressive eras such as the <a href="https://en.wikipedia.org/wiki/Age_of_Enlightenment" title="Age of Enlightenment">Enlightenment</a>.
The Enlightenment, a period in the history of 17th and 18th Century
Europe which was marked by dedication to progressive reform, natural
social hierarchies were reinforced, Europeans who were educated, white,
and native-born were considered high-class and less-educated,
non-European people were considered low-class. These natural hierarchies
were reinforced by progressives such as Marquis de Condorcet, a French
mathematician, who believed that slaves were savages due to their lack
of modern practices, despite the fact that he advocated the abolition of
slavery.
First, the colonization process usually works to attack the homes of
those who are being targeted. Typically, the people who are subjected to
colonizing practices are portrayed as lacking modernity, because they
and the colonialists do not have the same level of education or
technology.
</p><p>The term genocide was coined in the 20th century by <a href="https://en.wikipedia.org/wiki/Raphael_Lemkin" title="Raphael Lemkin">Raphael Lemkin</a> to describe the <a href="https://en.wikipedia.org/wiki/Armenian_genocide" title="Armenian genocide">Armenian genocide</a>, although <a href="https://en.wikipedia.org/wiki/Genocides_in_history" title="Genocides in history">genocides have been committed since ancient times</a>.
Years later, the term was unanimously accepted by the United Nations
and it was defined as an internationally illegal practice as a part of
Resolution 96 in 1946. Various definitions of genocide exist. However,
the Convention of Genocide has defined genocide as “acts committed with
intent to destroy, in whole or in part, a national, ethnical, racial or
religious group.” It is important to note that all definitions of
genocide involve ethnicity, race, or religion as a motivational factor. Genocide scholar <a href="https://en.wikipedia.org/wiki/Israel_Charny" title="Israel Charny">Israel Charny</a> has proposed a definition of genocide in the course of colonization.
</p><p>The example of <a href="https://en.wikipedia.org/wiki/Tasmania" title="Tasmania">Tasmania</a>
is cited, where white settlers wiped out indigenous Tasmanians, an
event which is genocide by definition as well as an event which is a
result of settler colonialism.
Additionally, instances of colonialism and genocide in California and
Hispaniola are cited below. The instance in California references the
colonization and genocide of indigenous tribes by euro-Americans during
the gold rush period.
The example in Hispaniola discusses the island's colonization by
Columbus and other Spaniards and the genocide inflicted on the native
Taino people.
</p>
<h2><span class="mw-headline" id="Researched_examples_of_genocide_linked_to_colonialism">Researched examples of genocide linked to colonialism</span></h2></div></div></div><ul><li>Another example of colonialism and Genocide is the genocide which was committed against the Taino tribe on <a href="https://en.wikipedia.org/wiki/Hispaniola" title="Hispaniola">Hispaniola</a> after the arrival of <a href="https://en.wikipedia.org/wiki/Christopher_Columbus" title="Christopher Columbus">Christopher Columbus</a> and other Spanish colonizers. Columbus and his crew arrived on the island of <a href="https://en.wikipedia.org/wiki/Haiti" title="Haiti">Haiti</a>
in December 1492. Initially leaving 39 Spaniards behind, Columbus left
and a year later, he returned with more Spaniards in order to complete
his conquest of the <a href="https://en.wikipedia.org/wiki/Dominican_Republic" title="Dominican Republic">Dominican Republic</a>.
There are no exact tallies of how many Taino people inhabited
Hispaniola when Columbus arrived on it. However, it is estimated that
the number of Taino people who lived on Hispaniola was at least hundreds
of thousands and it may have been up to a million or more. However,
during the 25 years when the Spanish colonized the islands of
Hispaniola, the Taino people were murdered, subjected to slavery, and by
the year 1514, only 32,000 Taino people remained alive. </li><li><a href="https://en.wikipedia.org/wiki/Black_War" title="Black War">Black War</a> of Tasmania, 1820s–1832. This was a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Guerrilla_war" title="Guerrilla war">guerrilla war</a> fought between <a href="https://en.wikipedia.org/wiki/Scramble_for_Africa" title="Scramble for Africa">European settlers</a> and <a href="https://en.wikipedia.org/wiki/Aboriginal_Tasmanians" title="Aboriginal Tasmanians">Aboriginal Tasmanians</a>, which resulted in the deaths of nearly 900 Aboriginal locals and the near extinction of the island's Aboriginal population.</li><li>According to Jack Norton, a <a href="https://en.wikipedia.org/wiki/Hupa" title="Hupa">Hupa</a> and <a href="https://en.wikipedia.org/wiki/Cherokee" title="Cherokee">Cherokee</a> scholar, the <a href="https://en.wikipedia.org/wiki/History_of_California_before_1900" title="History of California before 1900">colonization of California</a> was attributed to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Manifest_Destiny" title="Manifest Destiny">Manifest Destiny</a>, and the success of European colonizers in the West was attributed to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genocide_of_indigenous_peoples" title="Genocide of indigenous peoples">genocide of indigenous peoples</a>.
In a government-sponsored move to California, European colonizers
emigrated west to further colonize the north American continent due to
the discovery of gold in California. Upon arriving, Brendan Lindsay, an
American behavioral scientist, notes that the euro-American group
encountered nearly 150,000 indigenous tribes, and colonizers worked to
drive them away, murder them, or have them collected by militiamen or
vigilante forces. As the gold rush ended and as euro-American colonizers
began to cultivate the land and create democracy in California, the
treatment of indigenous tribes became much worse. The first California
Governor, Peter H. Burnett, declared that a “<a href="https://en.wikipedia.org/wiki/California_genocide" title="California genocide">war of extermination</a>” should be waged against Indians, the war was recounted by numerous newspapers which were published at that time.</li><li>According to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Tibetan_Government_in_Exile" title="Tibetan Government in Exile">Tibetan Government in Exile</a> (TGIE), during the early years of the rule of the <a href="https://en.wikipedia.org/wiki/History_of_Tibet_(1950%E2%80%93present)" title="History of Tibet (1950–present)">Chinese administration in Tibet</a>, an estimated 1.2 million Tibetans died between 1951 and 1984. Tibet expert <a href="https://en.wikipedia.org/wiki/Barry_Sautman" title="Barry Sautman">Barry Sautman</a>
considers this number highly "inaccurate," because there is "no
credible evidence of ongoing mass killing, physically enforced birth
control, or forced intermarriage in Tibet." Sautman also challenges the
notion that Chinese practices in Tibet can be considered genocidal or
colonial, stating that "Tibet's non-colonial nature can be derived from
the nature of modern colonialism" and citing the political and legal
equality of Tibetans under the current administration.</li><li>In Belgium, the <a href="https://en.wikipedia.org/wiki/Atrocities_in_the_Congo_Free_State" title="Atrocities in the Congo Free State">atrocities in the Congo Free State</a> are not in the public discourse, and the topic is not entirely addressed in education. The archive of the colony was destroyed. In 1999, <a href="https://en.wikipedia.org/wiki/Adam_Hochschild" title="Adam Hochschild">Adam Hochschild</a> published <i><a href="https://en.wikipedia.org/wiki/King_Leopold%27s_Ghost" title="King Leopold's Ghost">King Leopold's Ghost</a></i>, an award-winning book (and a documentary) about the atrocities committed in the <a href="https://en.wikipedia.org/wiki/Atrocities_in_the_Congo_Free_State" title="Atrocities in the Congo Free State">Congo Free State</a>. The <a href="https://en.wikipedia.org/wiki/American_Historical_Association" title="American Historical Association">American Historical Association</a> has awarded the book and claimed that Belgium has come to terms with this history because of the book.</li></ul>
<h2><span class="mw-headline" id="Settler_colonialism_and_genocide">Settler colonialism and genocide</span></h2><figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Mystic_Massacre_1637_Destruction_Of_The_Pequots_in_Connecticut.png"><img class="mw-file-element" data-file-height="952" data-file-width="1280" height="223" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/ac/Mystic_Massacre_1637_Destruction_Of_The_Pequots_in_Connecticut.png/300px-Mystic_Massacre_1637_Destruction_Of_The_Pequots_in_Connecticut.png" width="300" /></a><figcaption><b><a href="https://en.wikipedia.org/wiki/Mystic_massacre" title="Mystic massacre">Mystic Massacre</a> 1637</b></figcaption></figure>
<p>There is a number of international scholars whose work established a relation between <a href="https://en.wikipedia.org/wiki/Settler_colonialism" title="Settler colonialism">settler colonialism</a> and genocide, as seen below. Settler colonialism is different from immigration because immigrants
often assimilate into an existing society, not to destroy it to replace
it. <a href="https://en.wikipedia.org/wiki/Ann_Curthoys" title="Ann Curthoys">Ann Curthoys</a> is an Australian historian and academic who wrote about the view of genocide scholar <a href="https://en.wikipedia.org/wiki/Leo_Kuper" title="Leo Kuper">Leo Kuper</a>:
"Nevertheless, the course of colonization of North and South America,
the West Indies, and Australia and Tasmania, [Leo] Kuper observes, has
certainly been marked all too often by genocide." <a href="https://en.wikipedia.org/wiki/Noam_Chomsky" title="Noam Chomsky">Noam Chomsky</a> has considered settler colonialism to be the most vicious form of <a href="https://en.wikipedia.org/wiki/Imperialism" title="Imperialism">imperialism</a>, and describes the lack of self-awareness of the genocide by some Americans.
</p><p><a href="https://en.wikipedia.org/wiki/Pulitzer_Prize" title="Pulitzer Prize">Pulitzer Prize</a> winning historian <a href="https://en.wikipedia.org/wiki/Bernard_Bailyn" title="Bernard Bailyn">Bernard Baylin</a>
has said that the Dutch and English conquests were just as brutal as
those of the Spanish and Portuguese, in certain places and in certain
times "genocidal". He says that this history, for example the <a href="https://en.wikipedia.org/wiki/Pequot_War" title="Pequot War">Pequot War</a>, is not erased but conveniently forgotten. The different European colonizing powers were all similarly cruel in their dealings with Indigenous peoples.
</p><p><a href="https://en.wikipedia.org/wiki/David_Stannard" title="David Stannard">David Stannard</a>
historian and professor of American Studies at the University of Hawaii
analyzed the genocidal process in two cases of colonization. He said
that the British did not need massive labor as the Spanish, but land:
"And therein lies the central difference between the genocide committed
by the Spanish and that of the Anglo-Americans: in British America
extermination was the primary goal." Thus, in British America they would
clear the land of Indigenous peoples, and put the few survivors in
reserves.
</p><p><a href="https://en.wikipedia.org/wiki/Gregory_D._Smithers" title="Gregory D. Smithers">Gregory D. Smithers</a>, a lecturer in the Department of History at the <a href="https://en.wikipedia.org/wiki/University_of_Aberdeen" title="University of Aberdeen">University of Aberdeen</a>, has weighed in as well: "<a href="https://en.wikipedia.org/wiki/Ward_Churchill" title="Ward Churchill">Ward Churchill</a> refers to settler colonialism in North America as 'the American holocaust', and <a href="https://en.wikipedia.org/wiki/David_Stannard" title="David Stannard">David Stannard</a> similarly portrayed the European colonization of the Americas as an example of 'human incineration and carnage'."
</p><p><a href="https://en.wikipedia.org/wiki/Mark_Levene" title="Mark Levene">Mark Levene</a>, a historian at <a href="https://en.wikipedia.org/wiki/University_of_Southampton" title="University of Southampton">University of Southampton</a>,
linked colonialism and genocide: "In this, of course, we come back to
the fatal nexus between the Anglo-American drive to rapid state-building
and genocide." Levene has said that the authorities are silent about
genocide in the case of the colonization of Australia, even though the
press reports described the events.
</p><p><a href="https://en.wikipedia.org/wiki/Roxanne_Dunbar-Ortiz" title="Roxanne Dunbar-Ortiz">Roxanne Dunbar-Ortiz</a>, an American historian, professor at <a href="https://en.wikipedia.org/wiki/California_State_University" title="California State University">California State University</a>, describes settler colonialism as inherently genocidal from the perspective of the terms of the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>. She pointed out that genocide does not have to be total to be genocide, as the most famous genocide (the <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">Holocaust</a>) of all was not total.
</p><p>Stephen Howe, professor in the History and Cultures of Colonialism at the <a href="https://en.wikipedia.org/wiki/University_of_Bristol" title="University of Bristol">University of Bristol</a>, UK, relates colonialism with genocide and says the case for colonialism causing genocide is very strong.
</p><p><a href="https://en.wikipedia.org/wiki/Martin_Shaw_(sociologist)" title="Martin Shaw (sociologist)">Martin Shaw</a> has argued that in a colonial context: "each side shattered the opposing civilian population while pursuing military goals."
</p><p>Historian <a href="https://en.wikipedia.org/wiki/Jacques_Depelchin" title="Jacques Depelchin">Jacques Depelchin</a> has said that the crimes of colonization have always been denied.
</p><p>Christian P. Sherrer has argued that almost all European colonial powers used genocide as part of the colonization process. According to Elyse Semerdjian, settler colonial warfare is a slow genocidal process.</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-89572884890623622622024-03-17T07:15:00.000-04:002024-03-17T07:15:05.106-04:00Denial of genocides of Indigenous peoples<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"> <a href="https://en.wikipedia.org/wiki/Denial_of_genocides_of_Indigenous_peoples">https://en.wikipedia.org/wiki/Denial_of_genocides_of_Indigenous_peoples</a></div>
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<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Kingsborough.jpg"><img class="mw-file-element" data-file-height="1408" data-file-width="1220" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Kingsborough.jpg/150px-Kingsborough.jpg" width="347" /></a><figcaption>Spanish abuse at <a href="https://en.wikipedia.org/wiki/Encomienda" title="Encomienda">Encomienda</a> depicted in <a href="https://en.wikipedia.org/wiki/Codex_Kingsborough" title="Codex Kingsborough">Codex Kingsborough</a>, 16th century</figcaption></figure>
<p><b>Denial of genocides of Indigenous peoples</b> consists of a claim that has <a href="https://en.wikipedia.org/wiki/Historical_negationism" title="Historical negationism">denied</a> any of the multiple <a href="https://en.wikipedia.org/wiki/Genocide_of_Indigenous_peoples" title="Genocide of Indigenous peoples">genocides</a> and <a href="https://en.wikipedia.org/wiki/Atrocity_crime" title="Atrocity crime">atrocity crimes</a>, which have been committed against <a href="https://en.wikipedia.org/wiki/Indigenous_peoples" title="Indigenous peoples">Indigenous peoples</a>. The denialism claim contradicts the academic consensus, which acknowledges that genocide was committed. The claim is a form of <a href="https://en.wikipedia.org/wiki/Denialism" title="Denialism">denialism</a>, <a href="https://en.wikipedia.org/wiki/Genocide_denial" title="Genocide denial">genocide denial</a>, <a href="https://en.wikipedia.org/wiki/Historical_negationism" title="Historical negationism">historical negationism</a> and <a href="https://en.wikipedia.org/wiki/Historical_revisionism" title="Historical revisionism">historical revisionism</a>. The atrocity crimes include genocide, <a href="https://en.wikipedia.org/wiki/Crimes_against_humanity" title="Crimes against humanity">crimes against humanity</a>, <a href="https://en.wikipedia.org/wiki/War_crime" title="War crime">war crimes</a>, and <a href="https://en.wikipedia.org/wiki/Ethnic_cleansing" title="Ethnic cleansing">ethnic cleansing</a>.
</p><p>During European <a href="https://en.wikipedia.org/wiki/History_of_colonialism" title="History of colonialism">colonization</a>, many empires have colonized territories inhabited by what would be known today as Indigenous peoples. Many new colonies have <a href="https://en.wikipedia.org/wiki/Indigenous_response_to_colonialism" title="Indigenous response to colonialism">surviving Indigenous peoples</a> within their new political borders, and in this process, atrocities have been committed against Indigenous nations. The atrocities against Indigenous peoples have related to <a href="https://en.wikipedia.org/wiki/Forced_displacement" title="Forced displacement">forced displacement</a>, <a href="https://en.wikipedia.org/wiki/Exile" title="Exile">exile</a>, introduction of new diseases, forced containment in <a href="https://en.wikipedia.org/wiki/Indian_reservation" title="Indian reservation">reservations</a>, <a href="https://en.wikipedia.org/wiki/Forced_assimilation" title="Forced assimilation">forced assimilation</a>, <a href="https://en.wikipedia.org/wiki/Forced_labour" title="Forced labour">forced labour</a>, <a href="https://en.wikipedia.org/wiki/Criminalization" title="Criminalization">criminalization</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dispossession" title="Dispossession">dispossession</a>, <a href="https://en.wikipedia.org/wiki/Original_appropriation" title="Original appropriation">land theft</a>, <a href="https://en.wikipedia.org/wiki/Compulsory_sterilization" title="Compulsory sterilization">compulsory sterilization</a>, <a href="https://en.wikipedia.org/wiki/Trafficking_of_children" title="Trafficking of children">forcibly transferring children</a> of the group to another group, separating children from their families, <a href="https://en.wikipedia.org/wiki/Slavery" title="Slavery">enslavement</a>, captivity, <a href="https://en.wikipedia.org/wiki/Massacre" title="Massacre">massacres</a>, <a href="https://en.wikipedia.org/wiki/Forced_conversion" title="Forced conversion">forced religious conversion</a>, <a href="https://en.wikipedia.org/wiki/Cultural_genocide" title="Cultural genocide">cultural genocide</a>, and reduction of means of subsistence and subsequent <a href="https://en.wikipedia.org/wiki/Starvation" title="Starvation">starvation</a> and <a href="https://en.wikipedia.org/wiki/Disease" title="Disease">disease</a>.
</p><p>Non-Indigenous scholars are now increasingly examining the impact of <a href="https://en.wikipedia.org/wiki/Settler_colonialism" title="Settler colonialism">settler colonialism</a> and <a href="https://en.wikipedia.org/wiki/Internal_colonialism" title="Internal colonialism">internal colonialism</a> from the perspective of Indigenous peoples.
</p>
<h2><span class="mw-headline" id="Background">Background</span></h2></div></div></div><h3><span class="mw-headline" id="Defining_genocide">Defining genocide</span></h3><figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Massacre_at_Skull_Hole,_Mistake_Creek,_Australia.png"><img class="mw-file-element" data-file-height="1794" data-file-width="1210" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Massacre_at_Skull_Hole%2C_Mistake_Creek%2C_Australia.png/150px-Massacre_at_Skull_Hole%2C_Mistake_Creek%2C_Australia.png" width="270" /></a><figcaption>An 1888 drawing of a massacre by Queensland's police at Skull Hole, Mistake Creek, near <a href="https://en.wikipedia.org/wiki/Winton,_Queensland" title="Winton, Queensland">Winton, Australia</a>.</figcaption></figure>
<p>In 1948, the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>
defined genocide as any of five "acts committed with intent to destroy,
in whole or in part, a national, ethnical, racial or religious group".
These five acts include killing members of the group, causing them
serious bodily or mental harm, imposing living conditions intended to
destroy the group, preventing births, and forcibly transferring children
out of the group.<sup> </sup><a href="https://en.wikipedia.org/wiki/Genocide_definitions" title="Genocide definitions">Additional scholarly definitions</a> have been used to examine the diverse history of genocide, including those that include cultural and ethnic genocide as per <a href="https://en.wikipedia.org/wiki/Raphael_Lemkin" title="Raphael Lemkin">Raphael Lemkin</a>.
</p><p><a href="https://en.wikipedia.org/wiki/Edward_S._Herman" title="Edward S. Herman">Edward S. Herman</a> and <a href="https://en.wikipedia.org/wiki/Noam_Chomsky" title="Noam Chomsky">Noam Chomsky</a>
have argued that definitions of key terms, as well as the attention a
society provides to a specific issue, such as genocide, is the product
of mass media, as they mention in <i><a href="https://en.wikipedia.org/wiki/Manufacturing_Consent" title="Manufacturing Consent">Manufacturing Consent</a></i>:
"A propaganda system will consistently portray people abused in enemy
states as worthy victims, whereas those treated with equal or greater
severity by its own government or clients will be unworthy".
Thus, Chomsky views the term genocide as one that is used by those in
positions of political power and media prominence against their rivals,
but people in positions of power will avoid using the term to describe
their own actions, past and present.
</p><p>Bradley Campbell has proposed a theory of genocide as a function of minority status, social <a href="https://en.wikipedia.org/wiki/Geographical_segregation" title="Geographical segregation">segregation</a>, low population size, and lack of visibility. Further factors include <a href="https://en.wikipedia.org/wiki/Social_exclusion" title="Social exclusion">marginalization</a>, the lack of <a href="https://en.wikipedia.org/wiki/Political_representation" title="Political representation">political representation</a>, and lower economic or social <a href="https://en.wikipedia.org/wiki/Social_status" title="Social status">status</a>.
</p><p>In the latter part of the 20th century, the genocide of
Indigenous peoples attracted more attention from the international
community, including scholars and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Human_rights_organizations" title="Human rights organizations">human rights organizations</a>.
</p>
<h3><span class="mw-headline" id="Rationalization">Rationalization</span></h3><p>American academic and activist <a href="https://en.wikipedia.org/wiki/Gregory_Stanton" title="Gregory Stanton">Gregory Stanton</a>
has described ten stages of genocide, in which the ninth stage is
extermination and the tenth is denial. During this final stage, Stanton
argues that individuals and government may "deny that these crimes meet
the definition of genocide", "question whether intent to destroy a group
can be proven", and "often blame what happened on the victims". The concept of denial as the final stage of genocide has been discussed in more detail in the 2021 textbook <i>Denial: The Final Stage of Genocide?</i>
Stanton also indicates that stages often co-occur; the first eight
stages include classification, symbolization, discrimination,
dehumanization, organization, polarization, preparation, and
persecution. Early denial of genocide often occurred through these stages. For instance, American historian <a href="https://en.wikipedia.org/wiki/David_Stannard" title="David Stannard">David Stannard</a> explained that European colonizers "purposefully and systematically dehumaniz[ed] the people they were exterminating".
</p><p>Further, South African sociologist <a href="https://en.wikipedia.org/wiki/Leo_Kuper" title="Leo Kuper">Leo Kuper</a> has described denial as a routine defense, referring to it as a consequence of the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>.
He argues that denial has become more prevalent because genocide is
considered "an international crime with potentially significant <a href="https://en.wikipedia.org/wiki/Sanctions_(law)" title="Sanctions (law)">sanctions</a> by way of punishment, claims for reparation, and restitution of territorial rights".
</p>
<h2><span class="mw-headline" id="Denial_examples">Denial examples</span></h2><p>According to Robert K. Hitchcock, editor of <i>Modern Genocide</i>,
"the destruction of Indigenous peoples and their cultures has been a
policy of many of the world's governments, although most government
spokespersons argue that the disappearance or disruption of Indigenous
societies was not purposeful but rather occurred inadvertently."
Despite this, in 2013, Colin Leach et al. found that perpetrator groups
denied their group's responsibility, showed low levels of collective
guilt, and had low support for reparation policies.
</p>
<h3><span class="mw-headline" id="North_America">North America</span></h3><p>
According to a survey conducted between 2016 and 2018, "36% of Americans
almost certainly believe that the United States is guilty of committing
genocide against Native Americans."
Indigenous author Michelle A. Stanley writes that "Indigenous genocide
is largely denied, erased, relegated to the distant past, or presented
as inevitable". She writes that Indigenous genocide is depicted broadly,
without touching on the pattern of a series of separate genocides
against multiple distinct tribal nations. Seneca scholar Melissa Michal Slocum said that Native American genocide has been denied by the United States. </p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Battle_of_Washita_-_Sand_Creek_Massacre_by_Frederic_Remington.png"><img class="mw-file-element" data-file-height="1114" data-file-width="1500" height="296" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Battle_of_Washita_-_Sand_Creek_Massacre_by_Frederic_Remington.png/220px-Battle_of_Washita_-_Sand_Creek_Massacre_by_Frederic_Remington.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Sand_Creek_massacre" title="Sand Creek massacre">Sand Creek Massacre</a>, 1864</figcaption></figure><p>According to <i>North American Genocides</i>,
edited by Clarke et al., many American scholars deny Indigenous
genocide in the Americas, despite agreement from international scholars
that it occurred. American historian <a href="https://en.wikipedia.org/wiki/Ned_Blackhawk" title="Ned Blackhawk">Ned Blackhawk</a>
said that nationalist historiographies have been forms of denial that
erase the history of destruction of European colonial expansion.
Blackhawk said that near consensus has emerged that genocide against
some Indigenous peoples took place in North America following
colonization.
</p><p>Some historians do not consider that genocide of Indigenous peoples took place in North America, including <a href="https://en.wikipedia.org/wiki/James_Axtell" title="James Axtell">James Axtell</a>, <a href="https://en.wikipedia.org/wiki/Robert_M._Utley" title="Robert M. Utley">Robert Utley</a>, <a href="https://en.wikipedia.org/wiki/William_Rubinstein" title="William Rubinstein">William Rubinstein</a>, <a href="https://en.wikipedia.org/wiki/Guenter_Lewy" title="Guenter Lewy">Guenter Lewy</a> and Gary Anderson, although some call the atrocities another name such as ethnic cleansing.
Other scholars, including Elazar Barkan and Walter L. Hixson agree with
the sentiment that those in the Americas deny the genocide of the
regions' Indigenous populations.
</p><p>On the <a href="https://en.wikipedia.org/wiki/Columbus_Quincentenary" title="Columbus Quincentenary">Columbus Quincentenary</a>, American historian <a href="https://en.wikipedia.org/wiki/David_Stannard" title="David Stannard">David Stannard</a>
highlighted the numerous celebrations and festivities surrounding
Columbus alongside "American and European denials of culpability for the
most thoroughgoing genocide in the history of the world have assumed a
new guise." A similar issue arose when <a href="https://en.wikipedia.org/wiki/Lynne_Cheney" title="Lynne Cheney">Lynne Cheney</a>, then chair of the <a href="https://en.wikipedia.org/wiki/National_Endowment_for_the_Humanities" title="National Endowment for the Humanities">National Endowment for the Humanities</a>,
rejected a television project celebrating the anniversary, highlighted
the proposal's use of the word "genocide". Cheney stated, "We might be
interested in funding a film that debated that issue, but we are not
about to fund a film that asserts it. Columbus was guilty of many sins,
but he was not Hitler."
</p><p>
This particular issue, the comparison to <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">The Holocaust</a>, has been raised by others, as well, with American historian <a href="https://en.wikipedia.org/wiki/David_Stannard" title="David Stannard">David Stannard</a> pointing to <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">The Holocaust</a>'s prominent position in the public eye compared to the global ignorance of atrocities in the Americas. </p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Native_American_prisoners_at_the_old_Fort_St._Augustine_Florida_1875.jpg"><img class="mw-file-element" data-file-height="1080" data-file-width="1536" height="282" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/Native_American_prisoners_at_the_old_Fort_St._Augustine_Florida_1875.jpg/220px-Native_American_prisoners_at_the_old_Fort_St._Augustine_Florida_1875.jpg" width="400" /></a><figcaption>Indigenous prisoners of <a href="https://en.wikipedia.org/wiki/Red_River_War" title="Red River War">Red River War</a>, 1875.</figcaption></figure><p><a href="https://en.wikipedia.org/wiki/Howard_Zinn" title="Howard Zinn">Howard Zinn</a>, Susan Cameron, and Kirsten Dyck
have claimed that in American history textbooks, America's history of
abuse against Indigenous peoples is mostly ignored or presented from the
state's point of view.
</p><p>In <a class="mw-redirect" href="https://en.wikipedia.org/wiki/The_Other_Slavery:_The_Uncovered_Story_of_Indian_Enslavement_in_America" title="The Other Slavery: The Uncovered Story of Indian Enslavement in America"><i>The Other Slavery</i></a>, American historian <a href="https://en.wikipedia.org/wiki/Andr%C3%A9s_Res%C3%A9ndez" title="Andrés Reséndez">Andrés Reséndez</a>
compares the thousands of books written about the slavery of Africans
to the couple dozen books about Indigenous slavery and argues that the
latter has "almost completely erased from our historical memory". He
argues that African slavery is more widely accepted because it was
legalized and therefore recorded, whereas Indigenous slavery was largely
illegal; further, because African slaves needed to be transported,
settlers kept record of ship manifests.
</p><p>Canadian political scientist <a href="https://en.wikipedia.org/wiki/Adam_Jones_(Canadian_scholar)" title="Adam Jones (Canadian scholar)">Adam Jones</a> has said that the <a href="https://en.wikipedia.org/wiki/Historical_revisionism" title="Historical revisionism">historical revisionism</a> has been so thorough that in some cases, the Americas have been depicted as unpopulated before European colonization.
</p><p>Other claims against the genocide of Indigenous people of the
Americas deal with the natural superiority of the European colonizers.
For instance, Stannard has argued that British journalist <a href="https://en.wikipedia.org/wiki/Christopher_Hitchens" title="Christopher Hitchens">Christopher Hitchens</a>'s 1992 essay, "Minority Report", supported <a href="https://en.wikipedia.org/wiki/Social_Darwinism" title="Social Darwinism">social Darwinism</a>.
</p>
<h4><span class="mw-headline" id="California">California</span></h4><figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:%22Protecting_The_Settlers%22_Illustration_by_JR_Browne_for_his_work_%22The_Indians_Of_California%22_1864.jpg"><img alt="" class="mw-file-element" data-file-height="3029" data-file-width="1704" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/77/%22Protecting_The_Settlers%22_Illustration_by_JR_Browne_for_his_work_%22The_Indians_Of_California%22_1864.jpg/220px-%22Protecting_The_Settlers%22_Illustration_by_JR_Browne_for_his_work_%22The_Indians_Of_California%22_1864.jpg" width="225" /></a><figcaption>J.
Ross Browne, "Protecting the Settlers". 1861. This image accompanied an
article by Browne in which he described the killing of <a href="https://en.wikipedia.org/wiki/Yuki_people" title="Yuki people">Yuki people</a> at Round Valley, California.</figcaption></figure>
<p>Robert K. Hitchcock says that during the <a href="https://en.wikipedia.org/wiki/California_genocide" title="California genocide">California genocide</a>, "California state legislators, administrators, <a href="https://en.wikipedia.org/wiki/Indian_agent" title="Indian agent">Indian agents</a>, and townspeople denied that a genocide was happening."
</p><p>Continuing into the 21st century, Benjamin Madley has stated that
the California genocide has "too often concealed, denied, or
suppressed". This can be evidenced via social science and history textbooks approved by the <a href="https://en.wikipedia.org/wiki/California_Department_of_Education" title="California Department of Education">California Department of Education</a> that ignore the history of this genocide.
</p><p>In 2015, English writer and political activist <a href="https://en.wikipedia.org/wiki/George_Monbiot" title="George Monbiot">George Monbiot</a> argued that when the Catholic Church <a href="https://en.wikipedia.org/wiki/Canonization" title="Canonization">canonized</a> 18th-century Christian missionary <a href="https://en.wikipedia.org/wiki/Jun%C3%ADpero_Serra" title="Junípero Serra">Junípero Serra</a>, who "founded the system of <a href="https://en.wikipedia.org/wiki/Labor_camp" title="Labor camp">labour camps</a> that expedited California's <a href="https://en.wikipedia.org/wiki/Cultural_genocide" title="Cultural genocide">cultural genocide</a>", they were, in effect, denying the genocide.
</p>
<h4><span class="mw-headline" id="Canada">Canada</span></h4><p>Canada
has received many criticisms regarding its denial of participation in
Indigenous genocide, particularly in relation to the <a href="https://en.wikipedia.org/wiki/Canadian_Indian_residential_school_system" title="Canadian Indian residential school system">Canadian Indian residential school system</a>, and the long-term effects of both residential schooling and colonization more generally.
</p><p>The <a href="https://en.wikipedia.org/wiki/Canadian_Museum_for_Human_Rights" title="Canadian Museum for Human Rights">Canadian Museum for Human Rights</a>
(CMHR) received criticism upon its opening in 2014 because it did not
use the term genocide to describe the history of colonialism in Canada.
Two years after its opening, Rita K. Dhamoon critiqued the museum's
focus on the Holocaust, frame of residential schools as assimilationist
and not genocidal, and denial of the genocidal nature of settler
colonialism. In 2019, the museum reversed its policy and officially recognizes genocide of Indigenous peoples in Canada in its content.
</p><p>In 2021, Senator <a href="https://en.wikipedia.org/wiki/Lynn_Beyak" title="Lynn Beyak">Lynn Beyak</a>
generated controversy and was accused of genocide denial in the
Canadian Indian residential school system after she voiced disapproval
of the final <a href="https://en.wikipedia.org/wiki/Truth_and_Reconciliation_Commission_of_Canada" title="Truth and Reconciliation Commission of Canada">Truth and Reconciliation Commission of Canada</a> report, saying that it had omitted the positives of the school. Similarly, former <a href="https://en.wikipedia.org/wiki/Conservative_Party_of_Canada" title="Conservative Party of Canada">Conservative Party</a> leader <a href="https://en.wikipedia.org/wiki/Erin_O%27Toole" title="Erin O'Toole">Erin O'Toole</a> said that the residential school system educated Indigenous children,
but then changed his view: "The system was intended to remove children
from the influence of their homes, families, traditions, and cultures".
Former newspaper publisher <a href="https://en.wikipedia.org/wiki/Conrad_Black" title="Conrad Black">Conrad Black</a> and others have also been accused of denial.
</p><p>In 2022, <a href="https://en.wikipedia.org/wiki/Gregory_Stanton" title="Gregory Stanton">Gregory Stanton</a>, former president of <a href="https://en.wikipedia.org/wiki/International_Association_of_Genocide_Scholars" title="International Association of Genocide Scholars">International Association of Genocide Scholars</a>, issued a report of Canada's genocide saying it is in denial. On <a href="https://en.wikipedia.org/wiki/National_Day_for_Truth_and_Reconciliation" title="National Day for Truth and Reconciliation">National Truth and Reconciliation Day</a> in 2023, Trudeau said that denialism was on the rise.
</p>
<h5><span class="mw-headline" id="Response">Response</span></h5><p>In 2015, Supreme Court Chief Justice <a href="https://en.wikipedia.org/wiki/Beverley_McLachlin" title="Beverley McLachlin">Beverly McLachlin</a> said that Canada's historical treatment of Indigenous peoples was <a href="https://en.wikipedia.org/wiki/Cultural_genocide" title="Cultural genocide">cultural genocide</a>. In 2021, Canadian political scientist <a href="https://en.wikipedia.org/wiki/David_Bruce_MacDonald" title="David Bruce MacDonald">David Bruce MacDonald</a> argued that the Canadian government should recognize various atrocities committed against the Indigenous peoples in Canada. Later the same month, Prime Minister <a href="https://en.wikipedia.org/wiki/Justin_Trudeau" title="Justin Trudeau">Justin Trudeau</a> apologized in the context of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/2021_Canadian_Indian_residential_schools_gravesite_discoveries" title="2021 Canadian Indian residential schools gravesite discoveries">2021 Canadian Indian residential schools gravesite discoveries</a>.
</p><p>In 2022, the Canadian government announced that it would pay
C$31.5 billion to reform the foster care system and compensate
Indigenous families for its deficiencies. The government has acknowledged the overrepresentation of Indigenous children in the foster care system.
</p><p>In 2023, politician <a href="https://en.wikipedia.org/wiki/Leah_Gazan" title="Leah Gazan">Leah Gazan</a> has stated that she wants to criminalize the denial of genocide in residential schools. <a href="https://en.wikipedia.org/wiki/Scouts_Canada" title="Scouts Canada">Scouts Canada</a> also issued an apology for "its role in the eradication of First Nation, Inuit and Metis people for more than a century".
</p>
<h3><span class="mw-headline" id="South_America">South America</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Figueiredo_report,_commissioned_by_Brazil%E2%80%99s_Minister_of_the_Interior_in_1967.jpg"><img class="mw-file-element" data-file-height="1621" data-file-width="1170" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Figueiredo_report%2C_commissioned_by_Brazil%E2%80%99s_Minister_of_the_Interior_in_1967.jpg/220px-Figueiredo_report%2C_commissioned_by_Brazil%E2%80%99s_Minister_of_the_Interior_in_1967.jpg" width="289" /></a><figcaption>Atrocities against the <a href="https://en.wikipedia.org/wiki/Cinta_Larga" title="Cinta Larga">Cinta Larga</a> tribe in Brazil were exposed in the <a href="https://en.wikipedia.org/wiki/Figueiredo_Report" title="Figueiredo Report">Figueiredo report</a> of 1967. After shooting the head off her baby, the killers cut the mother in half.</figcaption></figure>
<p>According to Nadia Rubaii, the mass atrocities in Latin America have been less visible internationally for three reasons:
</p>
<ol><li>Victim groups have frequently been attacked for their
ideological or political differences, leading the international
community to consider such atrocities as domestic political issues.</li><li>Perpetrators who damage ecosystems and means of subsistence argue
that they are seeking economic development for common benefit and deny
the intention to inflict any harm.</li><li>If there is academic attention to the topic, it is documented in Spanish not in English.</li></ol>
<h4><span class="mw-headline" id="Argentina">Argentina</span></h4><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Popper_en_caceria.jpg"><img class="mw-file-element" data-file-height="712" data-file-width="982" height="160" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Popper_en_caceria.jpg/220px-Popper_en_caceria.jpg" width="220" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Julius_Popper" title="Julius Popper">Julius Popper</a> targeting Indigenous peoples. 1886. See <a href="https://en.wikipedia.org/wiki/Selk%27nam_genocide" title="Selk'nam genocide">Selk'nam Genocide</a>.</figcaption></figure>
<p>In Argentina, the <a href="https://en.wikipedia.org/wiki/Conquest_of_the_Desert" title="Conquest of the Desert">Conquest of the Desert</a> had been interpreted in war terms, silencing the fact of Indigenous genocide. In the case of the <a href="https://en.wikipedia.org/wiki/Napalp%C3%AD_massacre" title="Napalpí massacre">Napalmi massacre</a>, a judge concluded that the massacre took place in a context of genocide.
According to Walter Delrio et al. in 2010, "The state still denies the
existence of genocide and the existence of crimes against humanity with
respect to Indigenous peoples."
</p>
<h4><span class="mw-headline" id="Paraguay_and_Brazil">Paraguay and Brazil</span></h4><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Genocide_of_Indigenous_peoples_in_Brazil" title="Genocide of Indigenous peoples in Brazil">Genocide of Indigenous peoples in Brazil</a> and <a href="https://en.wikipedia.org/wiki/Genocide_of_Indigenous_peoples_in_Paraguay" title="Genocide of Indigenous peoples in Paraguay">Genocide of Indigenous peoples in Paraguay</a></div><p>South African sociologist and genocide scholar <a href="https://en.wikipedia.org/wiki/Leo_Kuper" title="Leo Kuper">Leo Kuper</a> says that genocide has been denied in Paraguay and Brazil on the basis of alleged lack of intent to destroy. For instance, the case of the <a href="https://en.wikipedia.org/wiki/Genocide_of_Indigenous_peoples_in_Paraguay" title="Genocide of Indigenous peoples in Paraguay">Ache</a> in Paraguay has been legally determined to be a case of political persecution.
</p><h3><span class="mw-headline" id="Central_America">Central America</span></h3><p>In Guatemala, debate has occurred over accusations of genocide. The <a href="https://en.wikipedia.org/wiki/Historical_Clarification_Commission" title="Historical Clarification Commission">Guatemalan Truth Commission</a> has reported genocide during the <a href="https://en.wikipedia.org/wiki/Guatemalan_Civil_War" title="Guatemalan Civil War">35 year civil war</a>, but some Guatemalan politicians have referred to the conflict as a civil war.
</p>
<h3><span class="mw-headline" id="Africa">Africa</span></h3><p>
The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Herero_and_Namaqua_genocide" title="Herero and Namaqua genocide">Herero genocide</a> is described as the first genocide of the 20th century. In 2012, German politician <a href="https://en.wikipedia.org/wiki/Uwe_Kekeritz" title="Uwe Kekeritz">Uwe Kekeritz</a> said Germany needed to move away from "a culture of denial".</p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Herero_and_Nama_prisoners.jpg"><img class="mw-file-element" data-file-height="1151" data-file-width="1920" height="240" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/Herero_and_Nama_prisoners.jpg/220px-Herero_and_Nama_prisoners.jpg" width="400" /></a><figcaption>Prisoners from the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Herero_and_Namaqua_genocide" title="Herero and Namaqua genocide">Herero and Nama genocide</a>, 1904-1907</figcaption></figure>
<h3><span class="mw-headline" id="Australia">Australia</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genocide_of_indigenous_peoples_in_Australia" title="Genocide of indigenous peoples in Australia">Genocide of indigenous peoples in Australia</a> and <a href="https://en.wikipedia.org/wiki/History_wars" title="History wars">History wars</a></div><p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Indigenous_Australian" title="Indigenous Australian">Indigenous Australian</a> population experienced the <a href="https://en.wikipedia.org/wiki/Australian_frontier_wars" title="Australian frontier wars">Australian frontier wars</a>, in which there was conflict over territory. <a href="https://en.wikipedia.org/wiki/List_of_massacres_of_Indigenous_Australians" title="List of massacres of Indigenous Australians">Massacres</a> and <a href="https://en.wikipedia.org/wiki/Mass_poisonings_of_Aboriginal_Australians" title="Mass poisonings of Aboriginal Australians">mass poisonings</a> have also been carried out against Indigenous people.
</p><p>According to Hannah Baldry, "The Australian Government appears to
have long suffered a form of 'denialism' that has consistently deprived
the country's Aboriginal population of acknowledgment of the crimes
perpetrated against their ancestors."
This includes ongoing debates about the interpretation of history,
including calling Australia's national myth as an invasion or
settlement.
</p><p>
Former Prime Minister <a href="https://en.wikipedia.org/wiki/John_Howard" title="John Howard">John Howard</a> refused to apologize in the <a href="https://en.wikipedia.org/wiki/Motion_of_Reconciliation" title="Motion of Reconciliation">Motion of Reconciliation</a>, claiming that the program had no genocidal intent. Former Tasmanian Premier <a href="https://en.wikipedia.org/wiki/Ray_Groom" title="Ray Groom">Ray Groom</a> said that "there had been no killing in the island state<i>".</i></p><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Aboriginal_slaves_Rottnest_1883.png"><img class="mw-file-element" data-file-height="889" data-file-width="1917" height="185" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Aboriginal_slaves_Rottnest_1883.png/220px-Aboriginal_slaves_Rottnest_1883.png" width="400" /></a><figcaption>Between 1838 and 1931, Aboriginal prisoners held on <a href="https://en.wikipedia.org/wiki/Rottnest_Island" title="Rottnest Island">Rottnest Island</a>, Australia were held in deplorable conditions and subjected to cruel and inhumane treatment.</figcaption></figure><p>The Australian literary and cultural journal <a href="https://en.wikipedia.org/wiki/Quadrant_(magazine)" title="Quadrant (magazine)"><i>Quadrant</i></a>
has been considered "a key locus of genocide denial". They included
common arguments regarding the definitional status of genocide,
including the idea "that 'half castes' could not claim Aboriginal status
since they were half-European" and that Indigenous people were to blame
for their fate due to "their own backwardness"; other articles argued
that "frontier massacres were based on misinterpreted statistics and
falsehoods".
</p><h2><span class="mw-headline" id="Reactions">Reactions</span></h2>A
number of states have chosen to take a firm stance against the denial of
genocide by enacting laws to criminalize it. The extent of legal
coverage varies from one state to another.<sup class="reference" id="cite_ref-124"><a href="https://en.wikipedia.org/wiki/Denial_of_genocides_of_Indigenous_peoples#cite_note-124"></a></sup>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-60831825584137453032024-03-17T06:54:00.002-04:002024-03-17T06:54:14.438-04:00Ocean acidification<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Ocean_acidification">https://en.wikipedia.org/wiki/Ocean_acidification</a> </div>
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<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Mean-seawater-ph.png"><img class="mw-file-element" data-file-height="2400" data-file-width="3400" height="282" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Mean-seawater-ph.png/350px-Mean-seawater-ph.png" width="400" /></a><figcaption>Ocean acidification means that the average ocean pH value is dropping over time.</figcaption></figure>
<p><b>Ocean acidification</b> is the ongoing decrease in the <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> of the Earth's <a href="https://en.wikipedia.org/wiki/Ocean" title="Ocean">ocean</a>. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_dioxide_emissions" title="Carbon dioxide emissions">Carbon dioxide emissions</a> from human activities are the primary cause of ocean acidification, with <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphere" title="Carbon dioxide in Earth's atmosphere">atmospheric carbon dioxide (CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>) levels</a> exceeding 410 ppm (in 2020). CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> from the <a href="https://en.wikipedia.org/wiki/Atmosphere" title="Atmosphere">atmosphere</a> is absorbed by the oceans. This chemical reaction produces <a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">carbonic acid</a> (<span class="chemf nowrap">H<sub class="template-chem2-sub">2</sub>CO<sub class="template-chem2-sub">3</sub></span>) which <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dissociate" title="Dissociate">dissociates</a> into a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bicarbonate_ion" title="Bicarbonate ion">bicarbonate ion</a> (<span class="chemf nowrap">HCO<span class="template-chem2-su"><span>−</span><span>3</span></span></span>) and a <a href="https://en.wikipedia.org/wiki/Hydrogen_ion" title="Hydrogen ion">hydrogen ion</a> (<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>). The presence of free hydrogen ions (<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>) lowers the pH of the ocean, increasing <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acidity</a> (this does not mean that <a href="https://en.wikipedia.org/wiki/Seawater" title="Seawater">seawater</a> is acidic yet; it is still <a href="https://en.wikipedia.org/wiki/Alkali" title="Alkali">alkaline</a>, with a pH higher than 8). <a href="https://en.wikipedia.org/wiki/Marine_biogenic_calcification" title="Marine biogenic calcification">Marine calcifying organisms</a>, such as <a href="https://en.wikipedia.org/wiki/Mollusca" title="Mollusca">mollusks</a> and <a href="https://en.wikipedia.org/wiki/Coral" title="Coral">corals</a>, are especially vulnerable because they rely on calcium carbonate to build shells and skeletons.
</p><p>A change in pH by 0.1 represents a 26% increase in hydrogen ion
concentration in the world's oceans (the pH scale is logarithmic, so a
change of one in pH units is equivalent to a tenfold change in hydrogen
ion concentration). Sea-surface pH and carbonate saturation states vary
depending on ocean depth and location. Colder and higher latitude waters
are capable of absorbing more CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>.
This can cause acidity to rise, lowering the pH and carbonate
saturation levels in these areas. Other factors that influence the
atmosphere-ocean CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> exchange, and thus local ocean acidification, include: <a href="https://en.wikipedia.org/wiki/Ocean_current" title="Ocean current">ocean currents</a> and <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a> zones, proximity to large continental rivers, <a href="https://en.wikipedia.org/wiki/Sea_ice" title="Sea ice">sea ice</a> coverage, and atmospheric exchange with nitrogen and sulfur from <a href="https://en.wikipedia.org/wiki/Fossil_fuel" title="Fossil fuel">fossil fuel burning</a> and <a href="https://en.wikipedia.org/wiki/Agriculture" title="Agriculture">agriculture.</a>
</p><p>Decreased ocean pH has a range of potentially harmful effects for
marine organisms. These include reduced calcification, depressed
metabolic rates, lowered immune responses, and reduced energy for basic
functions such as reproduction. The effects of ocean acidification are therefore impacting <a href="https://en.wikipedia.org/wiki/Marine_ecosystem" title="Marine ecosystem">marine ecosystems</a> that provide food, livelihoods, and other <a href="https://en.wikipedia.org/wiki/Ecosystem_service" title="Ecosystem service">ecosystem services</a>
for a large portion of humanity. Some 1 billion people are wholly or
partially dependent on the fishing, tourism, and coastal management
services provided by coral reefs. Ongoing acidification of the oceans
may therefore threaten <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Food_chains" title="Food chains">food chains</a> linked with the oceans.
</p><p>The United Nations <a href="https://en.wikipedia.org/wiki/Sustainable_Development_Goal_14" title="Sustainable Development Goal 14">Sustainable Development Goal 14</a> ("Life below Water") has a target to "minimize and address the impacts of ocean acidification". <a href="https://en.wikipedia.org/wiki/Sustainable_Development_Goal_13" title="Sustainable Development Goal 13">Reducing carbon dioxide emissions</a> (i.e., <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">climate change mitigation</a> measures) is the only solution that addresses the root cause of ocean acidification. Mitigation measures which achieve <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_removal" title="Carbon dioxide removal">carbon dioxide removal</a> from the atmosphere would help to reverse ocean acidification. The more specific <a href="https://en.wikipedia.org/wiki/Carbon_sequestration#Sequestration_techniques_in_oceans" title="Carbon sequestration">ocean-based mitigation methods</a> (e.g. ocean <a href="https://en.wikipedia.org/wiki/Alkalinity" title="Alkalinity">alkalinity</a> enhancement, <a href="https://en.wikipedia.org/wiki/Enhanced_weathering" title="Enhanced weathering">enhanced weathering</a>) could also reduce ocean acidification. These strategies are being researched, but generally have a low <a href="https://en.wikipedia.org/wiki/Technology_readiness_level" title="Technology readiness level">technology readiness level</a> and many risks.
</p><p>Ocean acidification has occurred previously in Earth's history. The resulting ecological collapse in the oceans had long-lasting effects on the <a href="https://en.wikipedia.org/wiki/Carbon_cycle" title="Carbon cycle">global carbon cycle</a> and <a href="https://en.wikipedia.org/wiki/Climate_variability_and_change" title="Climate variability and change">climate</a>.
</p>
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<h2><span class="mw-headline" id="Cause">Cause</span></h2></div></div></div><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Spatial_distribution_of_global_surface_ocean_pH.webp"><img class="mw-file-element" data-file-height="773" data-file-width="1000" height="309" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/54/Spatial_distribution_of_global_surface_ocean_pH.webp/260px-Spatial_distribution_of_global_surface_ocean_pH.webp.png" width="400" /></a><figcaption>Spatial
distribution of global surface ocean pH (Panel a: the annually-averaged
surface ocean pH to be approximate for the year 1770; Panel b: the
difference between pH in 2000 and 1770 in the global surface ocean).</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Carbon_cycle.jpg"><img class="mw-file-element" data-file-height="2192" data-file-width="2600" height="337" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Carbon_cycle.jpg/260px-Carbon_cycle.jpg" width="400" /></a><figcaption>This
diagram of the fast carbon cycle shows the movement of carbon between
land, atmosphere, and oceans. Yellow numbers are natural fluxes, and red
are human contributions in gigatons of carbon per year. White numbers
indicate stored carbon.</figcaption></figure>
<div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Oceanic_carbon_cycle" title="Oceanic carbon cycle">Oceanic carbon cycle</a></div><p>Present-day (2021) atmospheric carbon dioxide (CO<sub>2</sub>) levels of around 415 ppm are around 50% higher than preindustrial concentrations.
The current elevated levels and rapid growth rates are unprecedented in
the past 55 million years of the geological record. The sources of this
excess CO<sub>2</sub> are clearly established as human driven: they
include anthropogenic fossil fuel, industrial, and land-use/land-change
emissions. The ocean acts as a <a href="https://en.wikipedia.org/wiki/Carbon_sink" title="Carbon sink">carbon sink</a> for anthropogenic CO<sub>2</sub> and takes up roughly a quarter of total anthropogenic CO<sub>2</sub> emissions. However, the additional CO<sub>2</sub> in the ocean results in a wholesale shift in <a href="https://en.wikipedia.org/wiki/Seawater" title="Seawater">seawater</a>
acid-base chemistry toward more acidic, lower pH conditions and lower
saturation states for carbonate minerals used in many marine organism
shells and skeletons.
</p><p>Accumulated since 1850, the ocean sink holds up to
175 ± 35 gigatons of carbon, with more than two-thirds of this amount
(120 GtC) being taken up by the global ocean since 1960. Over the
historical period, the ocean sink increased in pace with the exponential
anthropogenic emissions increase. From 1850 until 2022, the ocean has
absorbed 26 % of total anthropogenic emissions.
Emissions during the period 1850–2021 amounted to 670 ± 65 gigatons of
carbon and were partitioned among the atmosphere (41 %), ocean (26 %),
and land (31 %).
</p><p>The <a href="https://en.wikipedia.org/wiki/Carbon_cycle" title="Carbon cycle">carbon cycle</a> describes the fluxes of carbon dioxide (<span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span>) between the oceans, <a href="https://en.wikipedia.org/wiki/Earth" title="Earth">terrestrial</a> <a href="https://en.wikipedia.org/wiki/Biosphere" title="Biosphere">biosphere</a>, <a href="https://en.wikipedia.org/wiki/Lithosphere" title="Lithosphere">lithosphere</a>, and <a href="https://en.wikipedia.org/wiki/Atmosphere" title="Atmosphere">atmosphere</a>. The carbon cycle involves both <a href="https://en.wikipedia.org/wiki/Organic_compound" title="Organic compound">organic compounds</a> such as <a href="https://en.wikipedia.org/wiki/Cellulose" title="Cellulose">cellulose</a> and inorganic carbon compounds such as <a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a>, <a href="https://en.wikipedia.org/wiki/Carbonate" title="Carbonate">carbonate ion</a>, and <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate ion</a>,
together referenced as dissolved inorganic carbon (DIC). These
inorganic compounds are particularly significant in ocean acidification,
as they include many forms of dissolved <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> present in the Earth's oceans.
</p><p>When <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (<span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2(aq)</sub></span></span>), <a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">carbonic acid</a> (<span class="chemf nowrap">H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span>CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>), <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate</a> (<span class="chemf nowrap">HCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>) and carbonate (<span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>). The ratio of these species depends on factors such as <a href="https://en.wikipedia.org/wiki/Seawater" title="Seawater">seawater</a> <a href="https://en.wikipedia.org/wiki/Temperature" title="Temperature">temperature</a>, pressure and salinity (as shown in a <a href="https://en.wikipedia.org/wiki/Bjerrum_plot" title="Bjerrum plot">Bjerrum plot</a>). These different forms of <a href="https://en.wikipedia.org/wiki/Total_inorganic_carbon" title="Total inorganic carbon">dissolved inorganic carbon</a> are transferred from an ocean's surface to its interior by the ocean's <a href="https://en.wikipedia.org/wiki/Solubility_pump" title="Solubility pump">solubility pump</a>. The resistance of an area of ocean to absorbing atmospheric <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> is known as the <a href="https://en.wikipedia.org/wiki/Revelle_factor" title="Revelle factor">Revelle factor</a>.
</p>
<h2><span class="mw-headline" id="Main_effects">Main effects</span></h2><p>The <a href="https://en.wikipedia.org/wiki/Marine_chemistry" title="Marine chemistry">ocean's chemistry</a> is changing due to the uptake of anthropogenic carbon dioxide (CO<sub>2</sub>).<sup class="reference nowrap"><span title="Page / location: 395"> </span></sup> Ocean pH, carbonate ion concentrations ([CO<sub>3</sub><sup>2−</sup>]),
and calcium carbonate mineral saturation states (Ω) have been declining
as a result of the uptake of approximately 30% of the anthropogenic
carbon dioxide emissions over the past 270 years (since around 1750).
This process, commonly referred to as "ocean acidification", is making
it harder for <a href="https://en.wikipedia.org/wiki/Marine_biogenic_calcification" title="Marine biogenic calcification">marine calcifiers</a> to build a shell or skeletal structure, endangering coral reefs and the broader marine ecosystems.
</p><p>Ocean acidification has been called the "evil twin of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Global_warming" title="Global warming">global warming</a>" and "the other CO<sub>2</sub> problem".
Increased ocean temperatures and oxygen loss act concurrently with
ocean acidification and constitute the "deadly trio" of climate change
pressures on the marine environment. The impacts of this will be most severe for coral reefs and other shelled marine organisms as well as those populations that depend on the ecosystem services they provide.
</p>
<h3><span class="mw-headline" id="Reduction_in_pH_value">Reduction in pH value</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Ocean#pH_and_alkalinity" title="Ocean">Ocean § pH and alkalinity</a></div><p>
Dissolving <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> in seawater increases the <a href="https://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">hydrogen</a> ion (<span class="chemf nowrap">H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: 0.8em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">+</sup><br /></span></span>) concentration in the ocean, and thus decreases ocean pH, as follows:</p><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> <sub>(aq)</sub> + H<sub>2</sub>O ⇌ H<sub>2</sub>CO<sub>3</sub> ⇌ HCO<sub>3</sub><sup>−</sup> + H<sup>+</sup> ⇌ CO<sub>3</sub><sup>2−</sup> + 2 H<sup>+</sup>.</div>
<p>In shallow coastal and shelf regions, a number of factors interplay to affect air-ocean CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> exchange and resulting pH change. These include biological processes, such as <a href="https://en.wikipedia.org/wiki/Photosynthesis" title="Photosynthesis">photosynthesis</a> and respiration, as well as water upwelling. Also, <a href="https://en.wikipedia.org/wiki/Stream_metabolism" title="Stream metabolism">ecosystem metabolism</a> in freshwater sources reaching coastal waters can lead to large, but local, pH changes.
</p><p>Freshwater bodies also appear to be acidifying, although this is a more complex and less obvious phenomenon.
</p><p>The absorption of CO<sub>2</sub> from the atmosphere does not affect the ocean's <a href="https://en.wikipedia.org/wiki/Alkalinity" title="Alkalinity">alkalinity</a>.<sup class="reference nowrap"><span title="Page / location: 2252"> </span></sup> This is important to know in this context as alkalinity is the capacity of <a href="https://en.wikipedia.org/wiki/Water" title="Water">water</a> to resist <a href="https://en.wikipedia.org/wiki/Freshwater_acidification" title="Freshwater acidification">acidification</a>. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_alkalinity_enhancement" title="Ocean alkalinity enhancement">Ocean alkalinity enhancement</a> has been proposed as one option to add alkalinity to the ocean and therefore buffer against pH changes.
</p>
<h3><span class="mw-headline" id="Decreased_calcification_in_marine_organisms">Decreased calcification in marine organisms</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Foraminifera_(265_36)_Various.jpg"><img class="mw-file-element" data-file-height="2400" data-file-width="3750" height="141" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Foraminifera_%28265_36%29_Various.jpg/220px-Foraminifera_%28265_36%29_Various.jpg" width="220" /></a><figcaption>Various types of <a href="https://en.wikipedia.org/wiki/Foraminifera" title="Foraminifera">foraminifera</a> observed through a microscope using differential interference contrast.</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Carbonate_system_of_seawater.svg"><img class="mw-file-element" data-file-height="334" data-file-width="540" height="248" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Carbonate_system_of_seawater.svg/260px-Carbonate_system_of_seawater.svg.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Bjerrum_plot" title="Bjerrum plot">Bjerrum plot</a>: Change in carbonate system of seawater from ocean acidification</figcaption></figure>
<p>Changes in ocean chemistry can have extensive direct and indirect
effects on organisms and their habitats. One of the most important
repercussions of increasing ocean acidity relates to the production of
shells out of <a href="https://en.wikipedia.org/wiki/Calcium_carbonate" title="Calcium carbonate">calcium carbonate</a> (<span class="chemf nowrap">CaCO<sub class="template-chem2-sub">3</sub></span>).
This process is called calcification and is important to the biology
and survival of a wide range of marine organisms. Calcification involves
the <a href="https://en.wikipedia.org/wiki/Precipitation_(chemistry)" title="Precipitation (chemistry)">precipitation</a> of dissolved ions into solid <span class="chemf nowrap">CaCO<sub class="template-chem2-sub">3</sub></span> structures, structures for many marine organisms, such as <a href="https://en.wikipedia.org/wiki/Coccolithophore" title="Coccolithophore">coccolithophores</a>, <a href="https://en.wikipedia.org/wiki/Foraminifera" title="Foraminifera">foraminifera</a>, <a href="https://en.wikipedia.org/wiki/Crustacean" title="Crustacean">crustaceans</a>, <a href="https://en.wikipedia.org/wiki/Mollusca" title="Mollusca">mollusks</a>, etc. After they are formed, these <span class="chemf nowrap">CaCO<sub class="template-chem2-sub">3</sub></span> structures are vulnerable to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dissolution_(chemistry)" title="Dissolution (chemistry)">dissolution</a> unless the surrounding seawater contains <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Saturated_solution" title="Saturated solution">saturating</a> concentrations of carbonate ions (<span class="chemf nowrap">CO<span class="template-chem2-su"><span>2−</span><span>3</span></span></span>).
</p><p>Very little of the extra carbon dioxide that is added into the
ocean remains as dissolved carbon dioxide. The majority dissociates into
additional bicarbonate and free hydrogen ions. The increase in hydrogen
is larger than the increase in bicarbonate, creating an imbalance in the reaction:
</p>
<dl><dd><span class="chemf nowrap">HCO<span class="template-chem2-su"><span>−</span><span>3</span></span> ⇌ CO<span class="template-chem2-su"><span>2−</span><span>3</span></span> + H<sup class="template-chem2-sup">+</sup></span></dd></dl>
<p>To maintain chemical equilibrium, some of the carbonate ions already
in the ocean combine with some of the hydrogen ions to make further
bicarbonate. Thus the ocean's concentration of carbonate ions is
reduced, removing an essential building block for marine organisms to
build shells, or calcify:
</p>
<dl><dd><span class="chemf nowrap">Ca<sup>2+</sup> + CO<span class="template-chem2-su"><span>2−</span><span>3</span></span> ⇌ CaCO<sub class="template-chem2-sub">3</sub></span></dd></dl>
<p>The increase in concentrations of dissolved carbon dioxide and bicarbonate, and reduction in carbonate, are shown in the <a href="https://en.wikipedia.org/wiki/Bjerrum_plot" title="Bjerrum plot">Bjerrum plot</a>.
</p>
<h3><span class="mw-headline" id="Decrease_in_saturation_state">Decrease in saturation state</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:CalciumAragoniteSaturation.jpg"><img class="mw-file-element" data-file-height="557" data-file-width="698" height="319" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/79/CalciumAragoniteSaturation.jpg/330px-CalciumAragoniteSaturation.jpg" width="400" /></a><figcaption>Distribution of (A) aragonite and (B) calcite saturation depth in the global oceans</figcaption></figure>
<p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Saturated_solution" title="Saturated solution">saturation</a>
state (known as Ω) of seawater for a mineral is a measure of the
thermodynamic potential for the mineral to form or to dissolve, and for
calcium carbonate is described by the following equation:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">Ω</mi>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo>[</mo>
<mrow>
<msup>
<mtext>Ca</mtext>
<mrow>
<mn>2</mn>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo>]</mo>
</mrow>
<mrow>
<mo>[</mo>
<mrow>
<msubsup>
<mtext>CO</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
<mo>]</mo>
</mrow>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mi>s</mi>
<mi>p</mi>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\Omega }={\frac {\left[{\ce {Ca^2+}}\right]\left[{\ce {CO3^2-}}\right]}{K_{sp}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0422ec8bbb280ae8547a20d486b928b0c21846f4" style="height: 6.843ex; vertical-align: -2.505ex; width: 20.871ex;" /></span></dd></dl>
<p>Here Ω is the product of the concentrations (or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_(chemistry)" title="Activity (chemistry)">activities</a>) of the reacting ions that form the mineral (Ca<sup>2+</sup> and CO<sub>3</sub><sup>2−</sup>), divided by the apparent solubility product at <a href="https://en.wikipedia.org/wiki/Chemical_equilibrium" title="Chemical equilibrium">equilibrium</a> (K<sub>sp</sub>), that is, when the rates of precipitation and dissolution are equal.
In seawater, dissolution boundary is formed as a result of temperature,
pressure, and depth, and is known as the saturation horizon. Above this saturation horizon, Ω has a value greater than 1, and <span class="chemf nowrap">CaCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span> does not readily dissolve. Most calcifying organisms live in such waters. Below this depth, Ω has a value less than 1, and <span class="chemf nowrap">CaCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span> will dissolve. The <a href="https://en.wikipedia.org/wiki/Carbonate_compensation_depth" title="Carbonate compensation depth">carbonate compensation depth</a>
is the ocean depth at which carbonate dissolution balances the supply
of carbonate to sea floor, therefore sediment below this depth will be
void of calcium carbonate. Increasing CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> levels, and the resulting lower pH of seawater, decreases the concentration of CO<sub>3</sub><sup>2−</sup> and the saturation state of <span class="chemf nowrap">CaCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span> therefore increasing <span class="chemf nowrap">CaCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span> dissolution.
</p><p>Calcium carbonate most commonly occurs in two common <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Polymorphism_(materials_science)" title="Polymorphism (materials science)">polymorphs</a> (crystalline forms): <a href="https://en.wikipedia.org/wiki/Aragonite" title="Aragonite">aragonite</a> and <a href="https://en.wikipedia.org/wiki/Calcite" title="Calcite">calcite</a>.
Aragonite is much more soluble than calcite, so the aragonite
saturation horizon, and aragonite compensation depth, is always nearer
to the surface than the calcite saturation horizon.
This also means that those organisms that produce aragonite may be more
vulnerable to changes in ocean acidity than those that produce calcite.
Ocean acidification and the resulting decrease in carbonate saturation
states raise the saturation horizons of both forms closer to the
surface.
This decrease in saturation state is one of the main factors leading to
decreased calcification in marine organisms because the inorganic
precipitation of <span class="chemf nowrap">CaCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>
is directly proportional to its saturation state and calcifying
organisms exhibit stress in waters with lower saturation states.
</p>
<h3><span class="mw-headline" id="Natural_variability_and_climate_feedbacks">Natural variability and climate feedbacks</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Carbonate_compensation_depth" title="Carbonate compensation depth">Carbonate compensation depth</a></div>
<p>Already now large quantities of water undersaturated in <a href="https://en.wikipedia.org/wiki/Aragonite" title="Aragonite">aragonite</a> are <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a> close to the Pacific <a href="https://en.wikipedia.org/wiki/Continental_shelf" title="Continental shelf">continental shelf</a> area of North America, from <a href="https://en.wikipedia.org/wiki/Vancouver" title="Vancouver">Vancouver</a> to <a href="https://en.wikipedia.org/wiki/Northern_California" title="Northern California">Northern California</a>. These continental shelves play an important role in marine ecosystems, since most <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marine_organisms" title="Marine organisms">marine organisms</a> live or are <a href="https://en.wikipedia.org/wiki/Spawn_(biology)" title="Spawn (biology)">spawned</a> there. Other shelf areas may be experiencing similar effects.
</p><p>At depths of 1000s of meters in the ocean, calcium carbonate
shells begin to dissolve as increasing pressure and decreasing
temperature shift the chemical equilibria controlling calcium carbonate
precipitation. The depth at which this occurs is known as the <a href="https://en.wikipedia.org/wiki/Carbonate_compensation_depth" title="Carbonate compensation depth">carbonate compensation depth</a>.
Ocean acidification will increase such dissolution and shallow the
carbonate compensation depth on timescales of tens to hundreds of years. Zones of <a href="https://en.wikipedia.org/wiki/Downwelling" title="Downwelling">downwelling</a> are being affected first.
</p><p>In the North Pacific and North Atlantic, saturation states are
also decreasing (the depth of saturation is getting more shallow).<sup class="reference nowrap"><span title="Page / location: 396"> </span></sup> Ocean acidification is progressing in the open ocean as the CO<sub>2</sub>
travels to deeper depth as a result of ocean mixing. In the open ocean,
this causes carbonate compensation depths to become more shallow,
meaning that dissolution of calcium carbonate will occur below those
depths. In the North Pacific these carbonate saturations depths are
shallowing at a rate of 1–2 m per year.<sup class="reference nowrap"><span title="Page / location: 396"> </span></sup>
</p><p>It is expected that ocean acidification in the future will lead
to a significant decrease in the burial of carbonate sediments for
several centuries, and even the dissolution of existing carbonate
sediments.
</p>
<h2><span class="mw-headline" id="Measured_and_estimated_values">Measured and estimated values</span></h2><h3><span class="mw-headline" id="Present_day_and_recent_history">Present day and recent history</span></h3><figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Co2_time_series_aloha_08-09-2023.jpg"><img class="mw-file-element" data-file-height="2526" data-file-width="3238" height="313" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/af/Co2_time_series_aloha_08-09-2023.jpg/220px-Co2_time_series_aloha_08-09-2023.jpg" width="400" /></a><figcaption>Time series of atmospheric CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> at Mauna Loa (in parts per million volume, ppmv; red), surface ocean pCO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> (µatm; blue) and surface ocean pH (green) at Ocean Station ALOHA in the subtropical North Pacific Ocean.</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:WOA05_GLODAP_del_pH_AYool.png"><img alt="World map showing the varying change to pH across different parts of different oceans" class="mw-file-element" data-file-height="1133" data-file-width="1683" height="269" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/WOA05_GLODAP_del_pH_AYool.png/290px-WOA05_GLODAP_del_pH_AYool.png" width="400" /></a><figcaption>Estimated change in seawater <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> caused by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Anthropogenic_impact" title="Anthropogenic impact">anthropogenic impact</a> on <a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide"><span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span></a> levels between the 1700s and the 1990s, from the <a href="https://en.wikipedia.org/wiki/Global_Ocean_Data_Analysis_Project" title="Global Ocean Data Analysis Project">Global Ocean Data Analysis Project</a> (GLODAP) and the <a href="https://en.wikipedia.org/wiki/World_Ocean_Atlas" title="World Ocean Atlas">World Ocean Atlas</a></figcaption></figure><p>Between 1950 and 2020, the average pH value of the ocean surface is estimated to have decreased from approximately 8.15 to 8.05.
This represents an increase of around 26% in hydrogen ion concentration
in the world's oceans (the pH scale is logarithmic, so a change of one
in pH unit is equivalent to a tenfold change in hydrogen ion
concentration.
For example, in the 15-year period 1995–2010 alone, acidity has
increased 6 percent in the upper 100 meters of the Pacific Ocean from
Hawaii to Alaska.
</p><p>The <a href="https://en.wikipedia.org/wiki/IPCC_Sixth_Assessment_Report" title="IPCC Sixth Assessment Report">IPCC Sixth Assessment Report</a>
in 2021 stated that "present-day surface pH values are unprecedented
for at least 26,000 years and current rates of pH change are
unprecedented since at least that time<sup class="reference nowrap"><span title="Page / location: 76"> </span></sup>.<sup class="reference nowrap"><span title="Page / location: 76"> </span></sup> The pH value of the ocean interior has declined over the last 20–30 years everywhere in the global ocean. The report also found that "pH in open ocean surface water has declined
by about 0.017 to 0.027 pH units per decade since the late 1980s".
</p><p>The rate of decline differs by region. This is due to complex interactions between different types of forcing mechanisms. "In the tropical Pacific, its central and eastern upwelling zones
exhibited a faster pH decline of minus 0.022 to minus 0.026 pH unit per
decade." This is thought to be "due to increased <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a> of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>-rich sub-surface waters in addition to anthropogenic CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> uptake."<sup class="reference nowrap"><span title="Page / location: 716"> </span></sup>
Some regions exhibited a slower acidification rate: a pH decline of
minus 0.010 to minus 0.013 pH unit per decade has been observed in warm
pools in the western tropical Pacific.
</p><p>The rate at which ocean acidification will occur may be influenced by the rate of <a href="https://en.wikipedia.org/wiki/Sea_surface_temperature" title="Sea surface temperature">surface ocean warming</a>, because warm waters will not absorb as much CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>. Therefore, greater seawater warming could limit CO<sub>2</sub> absorption and lead to a smaller change in pH for a given increase in CO<sub>2</sub>.
The difference in changes in temperature between basins is one of the
main reasons for the differences in acidification rates in different
localities.
</p><p>Current rates of ocean acidification have been likened to the greenhouse event at the <a href="https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum" title="Paleocene–Eocene Thermal Maximum">Paleocene–Eocene</a> boundary (about 56 million years ago), when surface ocean temperatures rose by 5–6 degrees <a href="https://en.wikipedia.org/wiki/Celsius" title="Celsius">Celsius</a>.
In that event, surface ecosystems experienced a variety of impacts, but
bottom-dwelling organisms in the deep ocean actually experienced a
major extinction.
Currently, the rate of carbon addition to the atmosphere-ocean system
is about ten times the rate that occurred at the Paleocene–Eocene
boundary.
</p><p>Extensive observational systems are now in place or being built for monitoring seawater CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> chemistry and acidification for both the global open ocean and some coastal systems.
</p>
<table border="1">
<caption>Rates of increasing acidity in different marine regions
</caption>
<thead><tr>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">Location</th>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">Change in pH units<br />per decade</th>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">Period</th>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">Data source
</th>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">Year of publication
</th></tr></thead><tbody>
<tr>
<td>Iceland</td>
<td>minus 0.024</td>
<td>1984–2009</td>
<td>Direct measurements
</td>
<td>2009
</td></tr>
<tr>
<td>Drake Passage</td>
<td>minus 0.018</td>
<td>2002–2012</td>
<td>Direct measurements
</td>
<td>2012
</td></tr>
<tr>
<td>Canary (ESTOC)</td>
<td>minus 0.017</td>
<td>1995–2004</td>
<td>Direct measurements
</td>
<td>2010
</td></tr>
<tr>
<td>Hawaii (<a href="https://en.wikipedia.org/wiki/Hawaii_Ocean_Time-series" title="Hawaii Ocean Time-series">HOT</a>)</td>
<td>minus 0.019</td>
<td>1989–2007</td>
<td>Direct measurements
</td>
<td>2009
</td></tr>
<tr>
<td>Bermuda (<a href="https://en.wikipedia.org/wiki/Bermuda_Atlantic_Time-series_Study" title="Bermuda Atlantic Time-series Study">BATS</a>)</td>
<td>minus 0.017</td>
<td>1984–2012</td>
<td>Direct measurements
</td>
<td>2012
</td></tr>
<tr>
<td>Coral Sea</td>
<td>minus 0.002</td>
<td>~1700 – ~1990</td>
<td>Proxy reconstruction
</td>
<td>2005
</td></tr>
<tr>
<td>Eastern Mediterranean</td>
<td>minus 0.023</td>
<td>1964–2005</td>
<td>Proxy reconstruction
</td>
<td>2016
</td></tr></tbody><tfoot></tfoot></table>
<table border="1"">
<caption><br />Rates of pH change for some regions of the world<br /></caption>
<tbody><tr>
<th>
<br /></th>
<th>Station, region
</th>
<th>Study period
</th>
<th>pH change<br />per decade
</th></tr>
<tr>
<td>Equatorial Pacific
</td>
<td>TAO
</td>
<td>2004–2011
</td>
<td>−0.026
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Indian_Ocean" title="Indian Ocean">Indian Ocean</a>
</td>
<td>IO-STPS
</td>
<td>1991–2011
</td>
<td>−0.027
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Mediterranean_Sea" title="Mediterranean Sea">Mediterranean</a>
</td>
<td>Dyfamed (43.42°N, 7.87°E)
</td>
<td>1995–2011
</td>
<td>−0.03
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/North_Atlantic" title="North Atlantic">North Atlantic</a>
</td>
<td><a href="https://en.wikipedia.org/wiki/Iceland_Sea" title="Iceland Sea">Iceland Sea</a> (68°N, 12.67°W)
</td>
<td>1985–2008<br />1985–2010
</td>
<td>−0.024<br />−0.014
</td></tr>
<tr>
<td>North Atlantic
</td>
<td><a href="https://en.wikipedia.org/wiki/Irminger_Sea" title="Irminger Sea">Irminger Sea</a> (64.3°N, 28°W)
</td>
<td>1983–2004
</td>
<td>−0.026
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/North_Pacific" title="North Pacific">North Pacific</a>
</td>
<td>NP-STSS
</td>
<td>1991–2011
</td>
<td>−0.01
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Southern_Ocean" title="Southern Ocean">Southern Ocean</a>
</td>
<td>PAL-LTER, west Antarctic Peninsula
</td>
<td>1993–2012
</td>
<td>+0.02
</td></tr></tbody></table>
<h3><span class="mw-headline" id="Geologic_past">Geologic past</span></h3><p>Ocean acidification has occurred previously in Earth's history. It happened during the <a href="https://en.wikipedia.org/wiki/Capitanian_mass_extinction_event" title="Capitanian mass extinction event">Capitanian mass extinction</a>, at the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Permian-Triassic_extinction_event" title="Permian-Triassic extinction event">end-Permian extinction</a>, during the <a href="https://en.wikipedia.org/wiki/Triassic%E2%80%93Jurassic_extinction_event" title="Triassic–Jurassic extinction event">end-Triassic extinction</a>, and during the <a href="https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event" title="Cretaceous–Paleogene extinction event">Cretaceous–Palaeogene extinction event</a>.
</p><p>Three of the big five mass extinction events in the geologic past
were associated with a rapid increase in atmospheric carbon dioxide,
probably due to <a href="https://en.wikipedia.org/wiki/Volcanism" title="Volcanism">volcanism</a> and/or thermal dissociation of marine <a href="https://en.wikipedia.org/wiki/Clathrate_hydrate" title="Clathrate hydrate">gas hydrates</a>. Elevated CO<sub>2</sub> levels impacted biodiversity. Decreased <span class="chemf nowrap">CaCO<sub class="template-chem2-sub">3</sub></span> saturation due to seawater uptake of volcanogenic CO<sub>2</sub> has been suggested as a possible kill mechanism during the marine mass extinction at the end of the <a href="https://en.wikipedia.org/wiki/Triassic" title="Triassic">Triassic</a>.
The end-Triassic biotic crisis is still the most well-established
example of a marine mass extinction due to ocean acidification, because
(a) carbon isotope records suggest enhanced volcanic activity that
decreased the carbonate sedimentation which reduced the carbonate
compensation depth and the carbonate saturation state, and a marine
extinction coincided precisely in the stratigraphic record, and (b) there was pronounced selectivity of the extinction against organisms with thick aragonitic skeletons, which is predicted from experimental studies. Ocean acidification has also been suggested as a one cause of the end-Permian mass extinction and the end-Cretaceous crisis. Overall, multiple climatic stressors, including ocean acidification, was likely the cause of geologic extinction events.
</p><p>The most notable example of ocean acidification is the <a href="https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum" title="Paleocene–Eocene Thermal Maximum">Paleocene-Eocene Thermal Maximum</a>
(PETM), which occurred approximately 56 million years ago when massive
amounts of carbon entered the ocean and atmosphere, and led to the
dissolution of carbonate sediments across many ocean basins. Relatively new geochemical methods of testing for pH in the past indicate the pH dropped 0.3 units across the PETM.
One study that solves the marine carbonate system for saturation state
shows that it may not change much over the PETM, suggesting the rate of
carbon release at our best geological analogy was much slower than
human-induced carbon emissions. However, stronger <a href="https://en.wikipedia.org/wiki/Proxy_(climate)" title="Proxy (climate)">proxy</a> methods to test for saturation state are needed to assess how much this pH change may have affected calcifying organisms.
</p>
<h2><span class="mw-headline" id="Predicted_future_values">Predicted future values</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Oa-sami.jpg"><img class="mw-file-element" data-file-height="1600" data-file-width="799" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Oa-sami.jpg/170px-Oa-sami.jpg" width="200" /></a><figcaption><i>In situ</i> <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> concentration sensor (SAMI-CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>),
attached to a Coral Reef Early Warning System station, utilized in
conducting ocean acidification studies near coral reef areas (by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/NOAA" title="NOAA">NOAA</a> (<a href="https://en.wikipedia.org/wiki/Atlantic_Oceanographic_and_Meteorological_Laboratory" title="Atlantic Oceanographic and Meteorological Laboratory">AOML</a>))</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Oa-buoy-enrique-reef.jpg"><img class="mw-file-element" data-file-height="1144" data-file-width="1964" height="233" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/Oa-buoy-enrique-reef.jpg/220px-Oa-buoy-enrique-reef.jpg" width="400" /></a><figcaption>A moored autonomous <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> buoy used for measuring <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> concentration and ocean acidification studies (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/NOAA" title="NOAA">NOAA</a> (by <a href="https://en.wikipedia.org/wiki/Pacific_Marine_Environmental_Laboratory" title="Pacific Marine Environmental Laboratory">PMEL</a>))</figcaption></figure>
<p>Importantly, the rate of change in ocean acidification is much higher
than in the geological past. This faster change prevents organisms from
gradually adapting, and prevents climate cycle feedbacks from kicking
in to mitigate ocean acidification. Ocean acidification is now on a path
to reach lower pH levels than at any other point in the last 300
million years.
The rate of ocean acidification (i.e. the rate of change in pH value)
is also estimated to be unprecedented over that same time scale. These expected changes are considered unprecedented in the geological record. In combination with other ocean <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Biogeochemical" title="Biogeochemical">biogeochemical</a>
changes, this drop in pH value could undermine the functioning of
marine ecosystems and disrupt the provision of many goods and services
associated with the ocean, beginning as early as 2100.
</p><p>The extent of further ocean chemistry changes, including ocean pH, will depend on <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">climate change mitigation</a> efforts taken by nations and their governments. Different scenarios of projected <a href="https://en.wikipedia.org/wiki/Socioeconomics" title="Socioeconomics">socioeconomic</a> global changes are modelled by using the <a href="https://en.wikipedia.org/wiki/Shared_Socioeconomic_Pathways" title="Shared Socioeconomic Pathways">Shared Socioeconomic Pathways</a> (SSP) scenarios.
</p><p>Under a <a href="https://en.wikipedia.org/wiki/Shared_Socioeconomic_Pathways" title="Shared Socioeconomic Pathways">very high emission scenario (SSP5-8.5)</a>,
model projections estimate that surface ocean pH could decrease by as
much as 0.44 units by the end of this century, compared to the end of
the 19th century.<sup class="reference nowrap"><span title="Page / location: 608"> </span></sup>
This would mean a pH as low as about 7.7, and represents a further
increase in H+ concentrations of two to four times beyond the increase
to date.
</p>
<table border="1">
<caption>Estimated past and future global mean surface pH for different emission scenarios
</caption>
<tbody><tr>
<th>Time period
</th>
<th>Ocean surface<br />pH value (approx.)
</th></tr>
<tr>
<td>Pre-industrial (1850)
</td>
<td>8.17
</td></tr>
<tr>
<td>Current (2021)
</td>
<td>8.08
</td></tr>
<tr>
<td>Future (2100) with low emission scenario (<a href="https://en.wikipedia.org/wiki/Shared_Socioeconomic_Pathways" title="Shared Socioeconomic Pathways">SSP</a> 1–2.6)
</td>
<td>8.0
</td></tr>
<tr>
<td>Future (2100) with very high emission scenario (<a href="https://en.wikipedia.org/wiki/Shared_Socioeconomic_Pathways" title="Shared Socioeconomic Pathways">SSP</a> 5–8.5)
</td>
<td>7.7
</td></tr></tbody></table>
<h2><span class="mw-headline" id="Impacts_on_oceanic_calcifying_organisms">Impacts on oceanic calcifying organisms</span></h2><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Marine_biogenic_calcification" title="Marine biogenic calcification">Marine biogenic calcification</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:A_pteropod_shell_is_shown_dissolving_over_time.jpg"><img class="mw-file-element" data-file-height="1080" data-file-width="1920" height="225" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/A_pteropod_shell_is_shown_dissolving_over_time.jpg/220px-A_pteropod_shell_is_shown_dissolving_over_time.jpg" width="400" /></a><figcaption>A <a href="https://en.wikipedia.org/wiki/Pteropoda" title="Pteropoda">pteropod</a>
shell is shown dissolving over time in seawater with a lower pH. When
carbon dioxide is absorbed by the ocean from the atmosphere, the
chemistry of the seawater is changed (source: <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">NOAA</a>)</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Pterapod_shell_dissolved_in_seawater_adjusted_to_an_ocean_chemistry_projected_for_the_year_2100.jpg"><img class="mw-file-element" data-file-height="566" data-file-width="1362" height="165" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Pterapod_shell_dissolved_in_seawater_adjusted_to_an_ocean_chemistry_projected_for_the_year_2100.jpg/220px-Pterapod_shell_dissolved_in_seawater_adjusted_to_an_ocean_chemistry_projected_for_the_year_2100.jpg" width="400" /></a><figcaption>Pterapod shell dissolved in seawater adjusted to an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ocean_chemistry" title="Ocean chemistry">ocean chemistry</a> projected for the year 2100 (source: <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">NOAA</a>).</figcaption></figure>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Fis01026_(27555118153).jpg"><img class="mw-file-element" data-file-height="2362" data-file-width="2718" height="347" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/95/Fis01026_%2827555118153%29.jpg/220px-Fis01026_%2827555118153%29.jpg" width="400" /></a><figcaption>Unhealthy
pteropod showing effects of ocean acidification including ragged,
dissolving shell ridges on upper surface, a cloudy shell in lower right
quadrant, and severe abrasions and weak spots at 6:30 position on lower
whorl of shell (source: <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">NOAA</a>).</figcaption></figure>
<h3><span class="mw-headline" id="Complexity_of_research_findings">Complexity of research findings</span></h3><p>The
full ecological consequences of the changes in calcification due to
ocean acidification are complex but it appears likely that many
calcifying species will be adversely affected by ocean acidification.<sup class="reference nowrap"><span title="Page / location: 413"> </span></sup>
Increasing ocean acidification makes it more difficult for
shell-accreting organisms to access carbonate ions, essential for the
production of their hard exoskeletal shell. Oceanic <a href="https://en.wikipedia.org/wiki/Calcification" title="Calcification">calcifying</a> organism span the <a href="https://en.wikipedia.org/wiki/Food_chain" title="Food chain">food chain</a> from <a href="https://en.wikipedia.org/wiki/Autotroph" title="Autotroph">autotrophs</a> to <a href="https://en.wikipedia.org/wiki/Heterotroph" title="Heterotroph">heterotrophs</a> and include organisms such as <a href="https://en.wikipedia.org/wiki/Coccolithophore" title="Coccolithophore">coccolithophores</a>, <a href="https://en.wikipedia.org/wiki/Coral" title="Coral">corals</a>, <a href="https://en.wikipedia.org/wiki/Foraminifera" title="Foraminifera">foraminifera</a>, <a href="https://en.wikipedia.org/wiki/Echinoderm" title="Echinoderm">echinoderms</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Crustacea" title="Crustacea">crustaceans</a> and <a href="https://en.wikipedia.org/wiki/Mollusca" title="Mollusca">molluscs</a>.</p><p>Overall, all marine ecosystems on Earth will be exposed to
changes in acidification and several other ocean biogeochemical changes.
Ocean acidification may force some organisms to reallocate resources
away from productive endpoints in order to maintain calcification. For example, the oyster <i><a href="https://en.wikipedia.org/wiki/Pacific_oyster" title="Pacific oyster">Magallana gigas</a></i> is recognized to experience metabolic changes alongside altered <a href="https://en.wikipedia.org/wiki/Calcification" title="Calcification">calcification</a> rates due to energetic tradeoffs resulting from pH imbalances.
</p><p>Under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ions are <a href="https://en.wikipedia.org/wiki/Supersaturation" title="Supersaturation">supersaturated</a>
with respect to seawater. However, as ocean pH falls, the concentration
of carbonate ions also decreases. Calcium carbonate thus becomes
undersaturated, and structures made of calcium carbonate are vulnerable
to calcification stress and dissolutionIn particular, studies show that corals, coccolithophores, coralline algae, foraminifera, shellfish and <a href="https://en.wikipedia.org/wiki/Pteropoda" title="Pteropoda">pteropods</a> experience reduced calcification or enhanced dissolution when exposed to elevated CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>. Even with active <a href="https://en.wikipedia.org/wiki/Marine_conservation" title="Marine conservation">marine conservation</a> practices it may be impossible to bring back many previous shellfish populations.
</p><p>Some studies have found different responses to ocean
acidification, with coccolithophore calcification and photosynthesis
both increasing under elevated atmospheric <a href="https://en.wikipedia.org/wiki/PCO2" title="PCO2">pCO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub></a>, and an equal decline in <a href="https://en.wikipedia.org/wiki/Primary_production" title="Primary production">primary production</a> and calcification in response to elevated CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>, or the direction of the response varying between species.
</p><p>Similarly, the sea star, <a href="https://en.wikipedia.org/wiki/Pisaster_ochraceus" title="Pisaster ochraceus">Pisaster ochraceus</a>, shows enhanced growth in waters with increased acidity.
</p><p>Reduced calcification from ocean acidification may affect the ocean's biologically driven sequestration of <a href="https://en.wikipedia.org/wiki/Carbon" title="Carbon">carbon</a> from the atmosphere to the ocean interior and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Seafloor_sediment" title="Seafloor sediment">seafloor sediment</a>, weakening the so-called <a href="https://en.wikipedia.org/wiki/Biological_pump" title="Biological pump">biological pump</a>. Seawater acidification could also reduce the size of Antarctic phytoplankton, making them less effective at storing carbon. Such changes are being increasingly studied and synthesized through the use of physiological frameworks, including the <a href="https://en.wikipedia.org/wiki/Adverse_outcome_pathway" title="Adverse outcome pathway">Adverse Outcome Pathway (AOP)</a> framework.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Coccolithus_pelagicus.jpg"><img class="mw-file-element" data-file-height="400" data-file-width="400" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/33/Coccolithus_pelagicus.jpg/220px-Coccolithus_pelagicus.jpg" width="400" /></a><figcaption><i>Coccolithus pelagicus,</i> a species of <a href="https://en.wikipedia.org/wiki/Coccolithophore" title="Coccolithophore">coccolithophore</a> sampled from the North Atlantic Ocean.</figcaption></figure>
<h3><span class="mw-headline" id="Coccolithophores">Coccolithophores</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Coccolithophore" title="Coccolithophore">Coccolithophore</a></div>
<p>A coccolithophore is a <a href="https://en.wikipedia.org/wiki/Unicellular_organism" title="Unicellular organism">unicellular</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eukaryotic" title="Eukaryotic">eukaryotic</a> <a href="https://en.wikipedia.org/wiki/Phytoplankton" title="Phytoplankton">phytoplankton</a> (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alga" title="Alga">alga</a>).
Understanding calcification changes in coccolithophores may be
particularly important because a decline in the coccolithophores may
have secondary effects on climate: it could contribute to global warming
by decreasing the Earth's <a href="https://en.wikipedia.org/wiki/Albedo" title="Albedo">albedo</a> via their effects on oceanic cloud cover. A study in 2008 examined a <a href="https://en.wikipedia.org/wiki/Sedimentology" title="Sedimentology">sediment core</a> from the <a href="https://en.wikipedia.org/wiki/Atlantic_Ocean" title="Atlantic Ocean">North Atlantic</a>
and found that the species composition of coccolithophorids remained
unchanged over the past 224 years (1780 to 2004). But the average
coccolith mass had increased by 40% during the same period.
</p>
<h3><span class="mw-headline" id="Corals">Corals</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Coral" title="Coral">Coral</a> and <a href="https://en.wikipedia.org/wiki/Coral_reef" title="Coral reef">Coral reef</a></div>
<p>Warm water corals are clearly in decline, with losses of 50% over the
last 30–50 years due to multiple threats from ocean warming, ocean
acidification, <a href="https://en.wikipedia.org/wiki/Marine_pollution" title="Marine pollution">pollution</a> and physical damage from activities such as fishing, and these pressures are expected to intensify.
</p><p>The fluid in the internal compartments (the coelenteron) where corals grow their <a href="https://en.wikipedia.org/wiki/Exoskeleton" title="Exoskeleton">exoskeleton</a>
is also extremely important for calcification growth. When the
saturation state of aragonite in the external seawater is at ambient
levels, the corals will grow their aragonite crystals rapidly in their
internal compartments, hence their exoskeleton grows rapidly. If the
saturation state of aragonite in the external seawater is lower than the
ambient level, the corals have to work harder to maintain the right
balance in the internal compartment. When that happens, the process of
growing the crystals slows down, and this slows down the rate of how
much their exoskeleton is growing. Depending on the aragonite saturation
state in the surrounding water, the corals may halt growth because
pumping aragonite into the internal compartment will not be
energetically favorable.
Under the current progression of carbon emissions, around 70% of North
Atlantic cold-water corals will be living in corrosive waters by
2050–60.
</p><p>Acidified conditions primarily reduce the coral's capacity to
build dense exoskeletons, rather than affecting the linear extension of
the exoskeleton. The density of some species of corals could be reduced
by over 20% by the end of this century.
</p><p>An <i>in situ</i> experiment, conducted on a 400 m2 patch of the <a href="https://en.wikipedia.org/wiki/Great_Barrier_Reef" title="Great Barrier Reef">Great Barrier Reef</a>, to decrease seawater CO<sub>2</sub> level (raise pH) to near the preindustrial value showed a 7% increase in net calcification. A similar experiment to raise in situ seawater CO<sub>2</sub> level (lower pH) to a level expected soon after the 2050 found that net calcification decreased 34%.
</p><p>However, a field study of the coral reef in <a href="https://en.wikipedia.org/wiki/Queensland" title="Queensland">Queensland</a> and <a href="https://en.wikipedia.org/wiki/Western_Australia" title="Western Australia">Western Australia</a>
from 2007 to 2012 found that corals are more resistant to the
environmental pH changes than previously thought, due to internal <a href="https://en.wikipedia.org/wiki/Homeostasis" title="Homeostasis">homeostasis</a> regulation; this makes thermal change (<a href="https://en.wikipedia.org/wiki/Marine_heatwave" title="Marine heatwave">marine heatwaves</a>), which leads to <a href="https://en.wikipedia.org/wiki/Coral_bleaching" title="Coral bleaching">coral bleaching</a>, rather than acidification, the main factor for coral reef vulnerability due to climate change.
</p>
<h4><span class="mw-headline" id="Studies_at_carbon_dioxide_seep_sites">Studies at carbon dioxide seep sites</span></h4><p>In
some places carbon dioxide bubbles out from the sea floor, locally
changing the pH and other aspects of the chemistry of the seawater.
Studies of these carbon dioxide seeps have documented a variety of
responses by different organisms.
Coral reef communities located near carbon dioxide seeps are of
particular interest because of the sensitivity of some corals species to
acidification. In <a href="https://en.wikipedia.org/wiki/Papua_New_Guinea" title="Papua New Guinea">Papua New Guinea</a>, declining pH caused by carbon dioxide seeps is associated with declines in coral species diversity. However, in <a href="https://en.wikipedia.org/wiki/Palau" title="Palau">Palau</a> carbon dioxide seeps are not associated with reduced species diversity of corals, although <a href="https://en.wikipedia.org/wiki/Bioerosion" title="Bioerosion">bioerosion</a> of coral skeletons is much higher at low pH sites.
</p>
<h3><span class="mw-headline" id="Pteropods_and_brittle_stars">Pteropods and brittle stars</span></h3><p><a href="https://en.wikipedia.org/wiki/Pteropoda" title="Pteropoda">Pteropods</a> and <a href="https://en.wikipedia.org/wiki/Brittle_star" title="Brittle star">brittle stars</a> both form the base of the Arctic <a href="https://en.wikipedia.org/wiki/Food_web" title="Food web">food webs</a>
and are both seriously damaged from acidification. Pteropods shells
dissolve with increasing acidification and the brittle stars lose muscle
mass when re-growing <a href="https://en.wikipedia.org/wiki/Appendage" title="Appendage">appendages</a>.
For pteropods to create shells they require aragonite which is produced
through carbonate ions and dissolved calcium and strontium. Pteropods
are severely affected because increasing acidification levels have
steadily decreased the amount of water supersaturated with carbonate.
The degradation of organic matter in Arctic waters has amplified ocean
acidification; some Arctic waters are already undersaturated with
respect to aragonite.
</p><p>The brittle star's eggs die within a few days when exposed to expected conditions resulting from Arctic acidification. Similarly, when exposed in experiments to pH reduced by 0.2 to 0.4, larvae of a temperate <a href="https://en.wikipedia.org/wiki/Brittle_star" title="Brittle star">brittle star</a>, a relative of the common <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sea_star" title="Sea star">sea star</a>, fewer than 0.1 percent survived more than eight days.
</p>
<h2><span class="mw-headline" id="Other_impacts_on_ecosystems">Other impacts on ecosystems</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Changes_in_aragonite_saturation_of_the_world%27s_oceans,_1880-2012_(US_EPA).png"><img class="mw-file-element" data-file-height="454" data-file-width="661" height="275" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Changes_in_aragonite_saturation_of_the_world%27s_oceans%2C_1880-2012_%28US_EPA%29.png/330px-Changes_in_aragonite_saturation_of_the_world%27s_oceans%2C_1880-2012_%28US_EPA%29.png" width="400" /></a><figcaption>This
map shows changes in the aragonite saturation level of ocean surface
waters between the 1880s and 2006–2015. Aragonite is a form of calcium
carbonate that many marine animals use to build their skeletons and
shells. The lower the saturation level, the more difficult it is for
organisms to build and maintain their skeletons and shells. A negative
change represents a decrease in saturation.</figcaption></figure>
<h3><span class="mw-headline" id="Other_biological_impacts">Other biological impacts</span></h3><p>Aside
from the slowing and/or reversal of calcification, organisms may suffer
other adverse effects, either indirectly through negative impacts on
food resources, or directly as reproductive or physiological effects. For example, the elevated oceanic levels of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> may produce <span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span>-induced acidification of body fluids, known as <a href="https://en.wikipedia.org/wiki/Hypercapnia" title="Hypercapnia">hypercapnia</a>.
Increasing acidity has been observed to reduce metabolic rates in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jumbo_squid" title="Jumbo squid">jumbo squid</a> and depress the immune responses of blue mussels.
<a class="new" href="https://en.wikipedia.org/w/index.php?title=Atlantic_longfin_squid&action=edit&redlink=1" title="Atlantic longfin squid (page does not exist)">Atlantic longfin squid</a> eggs took longer to hatch in acidified water, and the squid's <a href="https://en.wikipedia.org/wiki/Statocyst" title="Statocyst">statolith</a> was smaller and malformed in animals placed in sea water with a lower pH. However, these studies are ongoing and there is not yet a full understanding of these processes in marine organisms or <a href="https://en.wikipedia.org/wiki/Ecosystem" title="Ecosystem">ecosystems</a>.
</p>
<h4><span class="mw-headline" id="Acoustic_properties">Acoustic properties</span></h4><p>Another potential route to ecosystem impacts is through <a href="https://en.wikipedia.org/wiki/Bioacoustics" title="Bioacoustics">bioacoustics</a>. This may occur as ocean acidification can alter the <a href="https://en.wikipedia.org/wiki/Acoustics" title="Acoustics">acoustic</a> properties of seawater, allowing sound to propagate further, and increasing ocean noise. This impacts all animals that use sound for <a href="https://en.wikipedia.org/wiki/Animal_echolocation" title="Animal echolocation">echolocation</a> or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Whale_song" title="Whale song">communication</a>.
</p>
<h4><span class="mw-headline" id="Algae_and_seagrasses">Algae and seagrasses</span></h4><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Eutrophication" title="Eutrophication">Eutrophication</a></div>
<p>Another possible effect would be an increase in <a href="https://en.wikipedia.org/wiki/Harmful_algal_bloom" title="Harmful algal bloom">harmful algal bloom</a> events, which could contribute to the accumulation of toxins (<a href="https://en.wikipedia.org/wiki/Domoic_acid" title="Domoic acid">domoic acid</a>, <a href="https://en.wikipedia.org/wiki/Brevetoxin" title="Brevetoxin">brevetoxin</a>, <a href="https://en.wikipedia.org/wiki/Saxitoxin" title="Saxitoxin">saxitoxin</a>) in small organisms such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Anchovies" title="Anchovies">anchovies</a> and <a href="https://en.wikipedia.org/wiki/Shellfish" title="Shellfish">shellfish</a>, in turn increasing occurrences of <a href="https://en.wikipedia.org/wiki/Amnesic_shellfish_poisoning" title="Amnesic shellfish poisoning">amnesic shellfish poisoning</a>, <a href="https://en.wikipedia.org/wiki/Neurotoxic_shellfish_poisoning" title="Neurotoxic shellfish poisoning">neurotoxic shellfish poisoning</a> and <a href="https://en.wikipedia.org/wiki/Paralytic_shellfish_poisoning" title="Paralytic shellfish poisoning">paralytic shellfish poisoning</a>.
Although algal blooms can be harmful, other beneficial photosynthetic
organisms may benefit from increased levels of carbon dioxide. Most
importantly, seagrasses will benefit.
Research found that as seagrasses increased their photosynthetic
activity, calcifying algae's calcification rates rose, likely because
localized photosynthetic activity absorbed carbon dioxide and elevated
local pH.
</p>
<h4><span class="mw-headline" id="Fish_larvae">Fish larvae</span></h4><p>Ocean acidification can also have effects on marine <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Fish_larvae" title="Fish larvae">fish larvae</a>. It internally affects their olfactory systems, which is a crucial part of their early development. <a href="https://en.wikipedia.org/wiki/Orange_clownfish" title="Orange clownfish">Orange clownfish</a> larvae mostly live on oceanic reefs that are surrounded by vegetative islands.
Larvae are known to use their sense of smell to detect the differences
between reefs surrounded by vegetative islands and reefs not surrounded
by vegetative islands.
Clownfish larvae need to be able to distinguish between these two
destinations to be able to find a suitable area for their growth.
Another use for marine fish olfactory systems is to distinguish between
their parents and other adult fish, in order to avoid inbreeding.
</p><p>In an experimental aquarium facility, clownfish were sustained in
non-manipulated seawater with pH 8.15 ± 0.07, which is similar to our
current ocean's pH.
To test for effects of different pH levels, the seawater was modified
to two other pH levels, which corresponded with climate change models
that predict future atmospheric CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> levels. In the year 2100 the model projects possible CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> levels of 1,000 ppm, which correlates with the pH of 7.8 ± 0.05.
</p><p>This experiment showed that when larvae are exposed to a pH of
7.8 ± 0.05 their reaction to environmental cues differs drastically from
their reaction to cues at pH equal to current ocean levels. At pH 7.6 ± 0.05 larvae had no reaction to any type of cue. However, a <a href="https://en.wikipedia.org/wiki/Meta-analysis" title="Meta-analysis">meta-analysis</a> published in 2022 found that the <a href="https://en.wikipedia.org/wiki/Effect_size" title="Effect size">effect sizes</a>
of published studies testing for ocean acidification effects on fish
behavior have declined by an order of magnitude over the past decade,
and have been negligible for the past five years.
</p><p>Eel embryos, a "critically endangered" species yet profound in aquaculture, are also being affected by ocean acidification, specifically the <a href="https://en.wikipedia.org/wiki/European_eel" title="European eel">European eel</a>.
Although they spend most of their lives in fresh water, usually in
rivers, streams, or estuaries, they go to spawn and die in the <a href="https://en.wikipedia.org/wiki/Sargasso_Sea" title="Sargasso Sea">Sargasso Sea</a>. Here is where European eels are experiencing the effects of acidification in one of their key life stages.
</p><p>Fish embryos and larvae are usually more sensitive to pH changes
than adults, as organs for pH regulation are not full developed.
Because of this, European eel embryos are more vulnerable to changes in
pH in the Sargasso Sea. A study of the European Eel in the Sargasso Sea
was conducted in 2021 to analyze the specific effects of ocean
acidification on embryos. The study found that exposure to predicted
end-of-century ocean pCO<sub>2</sub> conditions may affect normal
development of this species in nature during sensitive early life
history stages with limited physiological response capacities, while
extreme acidification would negatively influence embryonic survival and
development under hatchery conditions.
</p>
<h3><span id="Compounded_effects_of_acidification.2C_warming_and_deoxygenation"></span><span class="mw-headline" id="Compounded_effects_of_acidification,_warming_and_deoxygenation">Compounded effects of acidification, warming and deoxygenation</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans">Effects of climate change on oceans</a> and <a href="https://en.wikipedia.org/wiki/Ocean_deoxygenation" title="Ocean deoxygenation">Ocean deoxygenation</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg"><img class="mw-file-element" data-file-height="348" data-file-width="429" height="324" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg/370px-Drivers_of_hypoxia_and_acidification_in_upwelling_shelf_systems.svg.png" width="400" /></a><figcaption>Drivers of <a href="https://en.wikipedia.org/wiki/Hypoxia_(environmental)" title="Hypoxia (environmental)">hypoxia</a> and ocean acidification intensification in <a href="https://en.wikipedia.org/wiki/Upwelling" title="Upwelling">upwelling</a> shelf systems. Equatorward winds drive the upwelling of low <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dissolved_oxygen" title="Dissolved oxygen">dissolved oxygen</a> (DO), high nutrient, and high <a href="https://en.wikipedia.org/wiki/Dissolved_inorganic_carbon" title="Dissolved inorganic carbon">dissolved inorganic carbon</a> (DIC) water from above the <a href="https://en.wikipedia.org/wiki/Oxygen_minimum_zone" title="Oxygen minimum zone">oxygen minimum zone</a>.
Cross-shelf gradients in productivity and bottom water residence times
drive the strength of DO (DIC) decrease (increase) as water transits
across a productive <a href="https://en.wikipedia.org/wiki/Continental_shelf" title="Continental shelf">continental shelf</a>.</figcaption></figure>
<p>There is a substantial body of research showing that a combination of ocean acidification and elevated <a href="https://en.wikipedia.org/wiki/Ocean_temperature" title="Ocean temperature">ocean temperature</a>
have a compounded effect on marine life and the ocean environment. This
effect far exceeds the individual harmful impact of either. In addition, ocean warming, along with increased productivity of phytoplankton from higher CO<sub>2</sub> levels exacerbates <a href="https://en.wikipedia.org/wiki/Ocean_deoxygenation" title="Ocean deoxygenation">ocean deoxygenation</a>. Deoxygenation of ocean waters is an additional stressor on marine organisms that increases <a href="https://en.wikipedia.org/wiki/Ocean_stratification" title="Ocean stratification">ocean stratification</a> therefore limiting nutrients over time and reducing biological gradients.
</p><p>Meta analyses have quantified the direction and magnitude of the
harmful effects of combined ocean acidification, warming and
deoxygenation on the ocean. These meta-analyses have been further tested by <a href="https://en.wikipedia.org/wiki/Mesocosm" title="Mesocosm">mesocosm</a>
studies that simulated the interaction of these stressors and found a
catastrophic effect on the marine food web: thermal stress more than
negates any primary producer to herbivore increase in productivity from
elevated CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>.
</p>
<h2><span class="mw-headline" id="Impacts_on_the_economy_and_societies">Impacts on the economy and societies</span></h2><p>The increase of ocean acidity decelerates the rate of calcification in salt water, leading to smaller and slower growing <a href="https://en.wikipedia.org/wiki/Coral_reef" title="Coral reef">coral reefs</a> which supports approximately 25% of marine life. Impacts are far-reaching from fisheries and coastal environments down to the deepest depths of the ocean.
The increase in ocean acidity in not only killing the coral, but also
the wildly diverse population of marine inhabitants which coral reefs
support.
</p>
<h3><span class="mw-headline" id="Fishing_and_tourism_industry">Fishing and tourism industry</span></h3><p>The threat of acidification includes a decline in <a href="https://en.wikipedia.org/wiki/Commercial_fishing" title="Commercial fishing">commercial fisheries</a> and the coast-based <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Tourism_industry" title="Tourism industry">tourism industry</a>.
Several ocean goods and services are likely to be undermined by future
ocean acidification potentially affecting the livelihoods of some 400 to
800 million people, depending upon the <a href="https://en.wikipedia.org/wiki/Shared_Socioeconomic_Pathways" title="Shared Socioeconomic Pathways">greenhouse gas emission scenario</a>.
</p><p>Some 1 billion people are wholly or partially dependent on the
fishing, tourism, and coastal management services provided by coral
reefs. Ongoing acidification of the oceans may therefore threaten future
<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Food_chains" title="Food chains">food chains</a> linked with the oceans.
</p>
<h4><span class="mw-headline" id="Arctic">Arctic</span></h4><p>In the
Arctic, commercial fisheries are threatened because acidification harms
calcifying organisms which form the base of the Arctic food webs
(pteropods and brittle stars, see above). Acidification threatens
Arctic food webs from the base up. Arctic food webs are considered
simple, meaning there are few steps in the food chain from small
organisms to larger predators. For example, pteropods are "a key prey
item of a number of higher predators – larger plankton, fish, seabirds,
whales".
Both pteropods and sea stars serve as a substantial food source and
their removal from the simple food web would pose a serious threat to
the whole ecosystem. The effects on the calcifying organisms at the base
of the food webs could potentially destroy fisheries.
</p>
<h4><span class="mw-headline" id="US_commercial_fisheries">US commercial fisheries</span></h4><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:R0023623_-_Flickr_-_NOAA_Photo_Library.jpg"><img class="mw-file-element" data-file-height="1188" data-file-width="1752" height="271" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/R0023623_-_Flickr_-_NOAA_Photo_Library.jpg/220px-R0023623_-_Flickr_-_NOAA_Photo_Library.jpg" width="400" /></a><figcaption>An adult <a href="https://en.wikipedia.org/wiki/American_lobster" title="American lobster">American lobster</a> rests on the sea floor. Rhode Island, Dutch Island, Newport County.</figcaption></figure>
<p>The value of fish caught from US commercial fisheries in 2007 was
valued at $3.8 billion and of that 73% was derived from calcifiers and
their direct predators.
Other organisms are directly harmed as a result of acidification. For
example, decrease in the growth of marine calcifiers such as the <a href="https://en.wikipedia.org/wiki/American_lobster" title="American lobster">American lobster</a>, <a href="https://en.wikipedia.org/wiki/Arctica_islandica" title="Arctica islandica">ocean quahog</a>, and <a href="https://en.wikipedia.org/wiki/Scallop" title="Scallop">scallops</a> means there is less shellfish meat available for sale and consumption.
Red king crab fisheries are also at a serious threat because crabs are
also calcifiers. Baby red king crab when exposed to increased
acidification levels experienced 100% mortality after 95 days.
In 2006, red king crab accounted for 23% of the total guideline harvest
levels and a serious decline in red crab population would threaten the
crab harvesting industry.
</p>
<h2><span class="mw-headline" id="Possible_responses">Possible responses</span></h2><h3><span class="mw-headline" id="Climate_change_mitigation">Climate change mitigation</span></h3><div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">Climate change mitigation</a>, <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_removal" title="Carbon dioxide removal">Carbon dioxide removal</a>, and <a href="https://en.wikipedia.org/wiki/Carbon_sequestration#Sequestration_techniques_in_oceans" title="Carbon sequestration">Carbon sequestration § Sequestration techniques in oceans</a></div>
<p>Reducing carbon dioxide emissions (i.e. <a href="https://en.wikipedia.org/wiki/Climate_change_mitigation" title="Climate change mitigation">climate change mitigation</a>
measures) is the only solution that addresses the root cause of ocean
acidification. For example, some mitigation measures focus on <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_removal" title="Carbon dioxide removal">carbon dioxide removal</a> (CDR) from the atmosphere (e.g. <a href="https://en.wikipedia.org/wiki/Direct_air_capture" title="Direct air capture">direct air capture</a> (DAC), <a href="https://en.wikipedia.org/wiki/Bioenergy_with_carbon_capture_and_storage" title="Bioenergy with carbon capture and storage">bioenergy with carbon capture and storage</a> (BECCS)). These would also slow the rate of acidification.
</p><p>Approaches that remove carbon dioxide from the ocean include <a href="https://en.wikipedia.org/wiki/Ocean_fertilization" title="Ocean fertilization">ocean nutrient fertilization</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Artificial_upwelling" title="Artificial upwelling">artificial upwelling</a>/downwelling, <a href="https://en.wikipedia.org/wiki/Seaweed_farming" title="Seaweed farming">seaweed farming</a>, ecosystem recovery, ocean alkalinity enhancement, <a href="https://en.wikipedia.org/wiki/Enhanced_weathering" title="Enhanced weathering">enhanced weathering</a> and electrochemical processes.<sup class="reference nowrap"><span title="Page / location: 12–36"> </span></sup> All of these methods use the ocean to remove CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>
from the atmosphere to store it in the ocean. These methods could
assist with mitigation but they can have side-effects on marine life.
The research field for all CDR methods has grown a lot since 2019.
</p><p>In total, "ocean-based methods have a combined potential to remove 1–100 gigatons of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> per year".<sup> </sup>Their costs are in the order of USD40–500 per ton of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>. For example, <a href="https://en.wikipedia.org/wiki/Enhanced_weathering" title="Enhanced weathering">enhanced weathering</a> could remove 2–4 gigatons of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> per year. This technology comes with a cost of 50–200 USD per ton of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>.
</p>
<h3><span class="mw-headline" id="Carbon_removal_technologies_which_add_alkalinity">Carbon removal technologies which add alkalinity</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Carbon_sequestration#Adding_bases_to_neutralize_acids" title="Carbon sequestration">Carbon sequestration § Adding bases to neutralize acids</a></div>
<p>Some <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_removal" title="Carbon removal">carbon removal</a>
techniques add alkalinity to the ocean and therefore immediately buffer
pH changes which might help the organisms in the region that the extra
alkalinity is added to. The two technologies that fall into this
category are ocean alkalinity enhancement and electrochemical methods. Eventually, due to diffusion, that alkalinity addition will be quite small to distant waters. This is why the term <i>local ocean acidification mitigation</i>
is used. Both of these technologies have the potential to operate on a
large scale and to be efficient at removing carbon dioxide.<sup class="reference nowrap"><span title="Page / location: Table 9.1"> </span></sup> However, they are expensive, have many risks and side effects and currently have a low <a href="https://en.wikipedia.org/wiki/Technology_readiness_level" title="Technology readiness level">technology readiness level</a>.
</p>
<h4><span class="mw-headline" id="Ocean_alkalinity_enhancement">Ocean alkalinity enhancement</span></h4><p>Ocean
alkalinity enhancement (OAE) is a proposed "carbon dioxide removal
(CDR) method that involves deposition of alkaline minerals or their
dissociation products at the ocean surface".<sup class="reference nowrap"><span title="Page / location: 2241"> </span></sup> The process would increase surface total alkalinity. It would work to increase ocean absorption of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>. The process involves increasing the amount of <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate</a> (HCO<sub>3</sub>-) through accelerated weathering (<a href="https://en.wikipedia.org/wiki/Enhanced_weathering" title="Enhanced weathering">enhanced weathering</a>) of rocks (<a href="https://en.wikipedia.org/wiki/Silicate" title="Silicate">silicate</a>, <a href="https://en.wikipedia.org/wiki/Limestone" title="Limestone">limestone</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Quicklime" title="Quicklime">quicklime</a>).<sup class="reference nowrap"><span title="Page / location: 181"> </span></sup> This process mimics the silicate-carbonate cycle. The CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> either becomes bicarbonate, remaining in that form for more than 100 years, or may precipitate into calcium carbonate (CaCO<sub>3</sub>). When calcium carbonate is buried in the deep ocean, it can hold the carbon indefinitely when utilizing silicate rocks.
</p><p>Enhanced weathering is one type of ocean alkalinity enhancement.
Enhanced weathering increases alkalinity by scattering fine rock
particles. This can happen on land and in the ocean (even though the
outcome eventually affects the ocean).
</p><p>In addition to sequestering CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>,
alkalinity addition buffers the pH of the ocean therefore reducing
ocean acidification. However, little is known about how organisms
respond to added alkalinity, even from natural sources. For example, weathering of some silicate rocks could release a large amount of trace metals at the weathering site.
</p><p>Cost and energy consumed by ocean alkalinity enhancement (mining,
pulverizing, transport) is high compared to other CDR techniques. The cost is estimated to be 20–50 USD per ton of CO<sub>2</sub> (for "direct addition of alkaline minerals to the ocean").
</p><p>Carbon sequestered as bicarbonate in the ocean amounts to about 30% of carbon emissions since the <a href="https://en.wikipedia.org/wiki/Industrial_Revolution" title="Industrial Revolution">Industrial Revolution</a>.
</p><p>Experimental materials include limestone, <a href="https://en.wikipedia.org/wiki/Brucite" title="Brucite">brucite</a>, <a href="https://en.wikipedia.org/wiki/Olivine" title="Olivine">olivine</a>
and alkaline solutions. Another approach is to use electricity to raise
alkalinity during desalination to capture waterborne CO2.
</p>
<h4><span class="mw-headline" id="Electrochemical_methods">Electrochemical methods</span></h4><p>Electrochemical methods, or <a href="https://en.wikipedia.org/wiki/Electrolysis" title="Electrolysis">electrolysis</a>, can strip carbon dioxide directly from seawater. Electrochemical process are a type of ocean alkalinity enhancement, too. Some methods focus on direct CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> removal (in the form of carbonate and CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> gas) while others increase the alkalinity of seawater by precipitating metal hydroxide residues, which absorbs CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>
in a matter described in the ocean alkalinity enhancement section. The
hydrogen produced during direct carbon capture can then be upcycled to
form hydrogen for energy consumption, or other manufactured laboratory
reagents such as <a href="https://en.wikipedia.org/wiki/Hydrochloric_acid" title="Hydrochloric acid">hydrochloric acid</a>.
</p><p>However, implementation of electrolysis for carbon capture is
expensive and the energy consumed for the process is high compared to
other CDR techniques.
In addition, research to assess the environmental impact of this
process is ongoing. Some complications include toxic chemicals in
wastewaters, and reduced DIC in effluents; both of these may negatively
impact marine life.
</p>
<h2><span class="mw-headline" id="Policies_and_goals">Policies and goals</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Save_our_ocean,_People%27s_Climate_March,_29_April_2017_(cropped).jpg"><img class="mw-file-element" data-file-height="2218" data-file-width="1568" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Save_our_ocean%2C_People%27s_Climate_March%2C_29_April_2017_%28cropped%29.jpg/170px-Save_our_ocean%2C_People%27s_Climate_March%2C_29_April_2017_%28cropped%29.jpg" width="283" /></a><figcaption>Demonstrator calling for action against ocean acidification at the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/People%27s_Climate_March_(2017)" title="People's Climate March (2017)">People's Climate March (2017)</a></figcaption></figure>
<h3><span class="mw-headline" id="Global_policies">Global policies</span></h3><p>As
awareness about ocean acidification grows, policies geared towards
increasing monitoring efforts of ocean acidification have been drafted. Previously in 2015, ocean scientist <a href="https://en.wikipedia.org/wiki/Jean-Pierre_Gattuso" title="Jean-Pierre Gattuso">Jean-Pierre Gattuso</a>
had remarked that "The ocean has been minimally considered at previous
climate negotiations. Our study provides compelling arguments for a
radical change at the UN conference (in Paris) on climate change".
</p><p>International efforts, such as the UN Cartagena Convention (entered into force in 1986),
are critical to enhance the support provided by regional governments to
highly vulnerable areas to ocean acidification. Many countries, for
example in the Pacific Islands and Territories, have constructed
regional policies, or National Ocean Policies, National Action Plans,
National Adaptation Plans of Action and Joint National Action Plans on
Climate Change and Disaster Risk Reduction, to help work towards <a href="https://en.wikipedia.org/wiki/Sustainable_Development_Goal_14" title="Sustainable Development Goal 14">SDG 14</a>. Ocean acidification is now starting to be considered within those frameworks.
</p>
<h4><span class="mw-headline" id="UN_Ocean_Decade">UN Ocean Decade</span></h4><p>The
UN Ocean Decade has a program called "Ocean acidification research for
sustainability". It was proposed by the Global Ocean Acidification
Observing Network (GOA-ON) and its partners, and has been formally
endorsed as a program of the UN Decade of Ocean Science for Sustainable
Development.
The OARS program builds on the work of GOA-ON and has the following
aims: to further develop the science of ocean acidification; to increase
observations of ocean chemistry changes; to identify the impacts on
marine ecosystems on local and global scales; and to provide decision
makers with the information needed to mitigate and adapt to ocean
acidification.
</p>
<h4><span class="mw-headline" id="Global_Climate_Indicators">Global Climate Indicators</span></h4><p>The importance of ocean acidification is reflected in its inclusion as one of seven Global Climate Indicators. These Indicators are a set of parameters that describe the changing climate without reducing climate change to only <a href="https://en.wikipedia.org/wiki/Instrumental_temperature_record" title="Instrumental temperature record">rising temperature</a>.
The Indicators include key information for the most relevant domains of
climate change: temperature and energy, atmospheric composition, ocean
and water as well as the cryosphere. The Global Climate Indicators have
been identified by scientists and communication specialists in a process
led by <a href="https://en.wikipedia.org/wiki/Global_Climate_Observing_System" title="Global Climate Observing System">Global Climate Observing System</a> (GCOS). The Indicators have been endorsed by the <a href="https://en.wikipedia.org/wiki/World_Meteorological_Organization" title="World Meteorological Organization">World Meteorological Organization</a> (WMO). They form the basis of the annual WMO Statement of the State of the Global Climate, which is submitted to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Conferences_of_the_Parties_of_UNFCCC_and_the_Kyoto_Protocol" title="Conferences of the Parties of UNFCCC and the Kyoto Protocol">Conference of Parties</a> (COP) of the <a href="https://en.wikipedia.org/wiki/United_Nations_Framework_Convention_on_Climate_Change" title="United Nations Framework Convention on Climate Change">United Nations Framework Convention on Climate Change</a> (UNFCCC). Additionally, the <a href="https://en.wikipedia.org/wiki/Copernicus_Climate_Change_Service" title="Copernicus Climate Change Service">Copernicus Climate Change Service</a> (C3S) of the European Commission uses the Indicators for their annual "European State of the Climate".
</p>
<h4><span class="mw-headline" id="Sustainable_Development_Goal_14">Sustainable Development Goal 14</span></h4><p>In
2015, the United Nations adopted the 2030 Agenda and a set of 17
Sustainable Development Goals (SDG), including a goal dedicated to the
ocean, <a href="https://en.wikipedia.org/wiki/Sustainable_Development_Goal_14" title="Sustainable Development Goal 14">Sustainable Development Goal 14</a>,
which calls to "conserve and sustainably use the oceans, seas and
marine resources for sustainable development". Ocean acidification is
directly addressed by the target SDG 14.3. The full title of Target 14.3
is: "Minimize and address the impacts of ocean acidification, including
through enhanced scientific cooperation at all levels". This target has one indicator: Indicator 14.3.1 which calls for the "Average marine acidity (<a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a>) measured at agreed suite of representative sampling stations".
</p><p>The <a href="https://en.wikipedia.org/wiki/Intergovernmental_Oceanographic_Commission" title="Intergovernmental Oceanographic Commission">Intergovernmental Oceanographic Commission</a> (IOC) of <a href="https://en.wikipedia.org/wiki/UNESCO" title="UNESCO">UNESCO</a>
was identified as the custodian agency for the SDG 14.3.1 Indicator. In
this role, IOC-UNESCO is tasked with developing the SDG 14.3.1
Indicator Methodology, the annual collection of data towards the SDG
14.3.1 Indicator and the reporting of progress to the United Nations.
</p>
<h3><span class="mw-headline" id="Policies_at_country_level">Policies at country level</span></h3><h4><span class="mw-headline" id="United_States">United States</span></h4><p>In
the United States, the Federal Ocean Acidification Research And
Monitoring Act of 2009 supports government coordination, such as the <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">National Oceanic Atmospheric Administration</a>'s (NOAA) "Ocean Acidification Program". In 2015, USEPA denied a citizens petition that asked EPA to regulate CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> under the <a href="https://en.wikipedia.org/wiki/Toxic_Substances_Control_Act_of_1976" title="Toxic Substances Control Act of 1976">Toxic Substances Control Act of 1976</a> in order to mitigate ocean acidification. In the denial, the EPA said that risks from ocean acidification were
being "more efficiently and effectively addressed" under domestic
actions, e.g., under the <a href="https://en.wikipedia.org/wiki/Presidential_Climate_Action_Plan" title="Presidential Climate Action Plan">Presidential Climate Action Plan</a>,
and that multiple avenues are being pursued to work with and in other
nations to reduce emissions and deforestation and promote clean energy
and energy efficiency.
</p>
<h2><span class="mw-headline" id="History">History</span></h2><p>Research
into the phenomenon of ocean acidification, as well as awareness
raising about the problem, has been going on for several decades. The
fundamental research really began with the creation of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ph_scale" title="Ph scale">pH scale</a> by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Danish_people" title="Danish people">Danish</a> chemist <a class="mw-redirect" href="https://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensen" title="Søren Peder Lauritz Sørensen">Søren Peder Lauritz Sørensen</a> in 1909. By around the 1950s the massive role of the ocean in absorbing fossil fuel CO<sub>2</sub> was known to specialists, but not appreciated by the greater scientific community. Throughout much of the 20th century, the dominant focus has been the beneficial process of oceanic CO<sub>2</sub>
uptake, which has enormously ameliorated climate change. The concept of
"too much of a good thing" has been late in developing and was
triggered only by some key events, and the <a href="https://en.wikipedia.org/wiki/Carbon_sink" title="Carbon sink">oceanic sink</a> for heat and CO<sub>2</sub> is still critical as the primary buffer against climate change.
</p><p>In the early 1970s questions over the long-term impact of the accumulation of fossil fuel CO<sub>2</sub>
in the sea were already arising around the world and causing strong
debate. Researchers commented on the accumulation of fossil CO<sub>2</sub> in the atmosphere and sea and drew attention to the possible impacts on marine life. By the mid-1990s, the likely impact of CO<sub>2</sub>
levels rising so high with the inevitable changes in pH and carbonate
ion became a concern of scientists studying the fate of coral reefs.
</p><p>By the end of the 20th century the trade-offs between the
beneficial role of the ocean in absorbing some 90 % of all heat created,
and the accumulation of some 50 % of all fossil fuel CO<sub>2</sub>
emitted, and the impacts on marine life were becoming more clear. By
2003, the time of planning for the "First Symposium on the Ocean in a
High-CO<sub>2</sub> World" meeting to be held in Paris in 2004, many new research results on ocean acidification were published.
</p><p>In 2009, members of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/InterAcademy_Panel" title="InterAcademy Panel">InterAcademy Panel</a> called on world leaders to "Recognize that reducing the build up of CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> in the atmosphere is the only practicable solution to mitigating ocean acidification". The statement also stressed the importance to "Reinvigorate action to reduce stressors, such as <a href="https://en.wikipedia.org/wiki/Overfishing" title="Overfishing">overfishing</a> and <a href="https://en.wikipedia.org/wiki/Marine_pollution" title="Marine pollution">pollution</a>, on <a href="https://en.wikipedia.org/wiki/Marine_ecosystem" title="Marine ecosystem">marine ecosystems</a> to increase resilience to ocean acidification".
</p><p>For example, research in 2010 found that in the 15-year period
1995–2010 alone, acidity had increased 6 percent in the upper 100 meters
of the Pacific Ocean from Hawaii to Alaska.
</p><p>According to a statement in July 2012 by <a href="https://en.wikipedia.org/wiki/Jane_Lubchenco" title="Jane Lubchenco">Jane Lubchenco</a>, head of the U.S. <a href="https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration" title="National Oceanic and Atmospheric Administration">National Oceanic and Atmospheric Administration</a>
"surface waters are changing much more rapidly than initial
calculations have suggested. It's yet another reason to be very
seriously concerned about the amount of carbon dioxide that is in the
atmosphere now and the additional amount we continue to put out."
</p><p>A 2013 study found acidity was increasing at a rate 10 times faster than in any of the evolutionary crises in Earth's history.
</p><p>The "Third Symposium on the Ocean in a High-CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub>
World" took place in Monterey, California, in 2012. The summary for
policy makers from the conference stated that "Ocean acidification
research is growing rapidly".
</p><p>In a synthesis report published in <i>Science</i> in 2015, 22 leading marine scientists stated that CO<sub style="font-size: 80%; vertical-align: -0.35em;">2</sub> from burning fossil fuels is changing the oceans' chemistry more rapidly than at any time since the <a href="https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event" title="Permian–Triassic extinction event">Great Dying</a> (Earth's most severe known extinction event).
Their report emphasized that the 2 °C maximum temperature increase
agreed upon by governments reflects too small a cut in emissions to
prevent "dramatic impacts" on the world's oceans.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-53125229539659737602024-03-16T16:52:00.002-04:002024-03-16T16:52:38.053-04:00Genocide recognition politics<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics">https://en.wikipedia.org/wiki/Genocide_recognition_politics</a></div><div class="noprint" id="siteSub"> </div><div class="noprint" id="siteSub"><b>Genocide recognition politics</b> are efforts to have a certain event (re)interpreted as a "<a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>" or officially designated as such. Such efforts may occur regardless of whether the event meets the definition of genocide laid out in the 1948 <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>.
<p>In countries with settler colonial past, recognition of colonial
genocides is difficult as the national past could be called into
question. Most genocides have been perpetrated by states.
</p>
<h2><span class="mw-headline" id="By_country">By country</span></h2></div></div></div><h3><span class="mw-headline" id="Canada">Canada</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Indian_Residential_Schools_Settlement_Agreement" title="Indian Residential Schools Settlement Agreement">Indian Residential Schools Settlement Agreement</a>, <a href="https://en.wikipedia.org/wiki/Truth_and_Reconciliation_Commission_of_Canada" title="Truth and Reconciliation Commission of Canada">Truth and Reconciliation Commission of Canada</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Canadian_Indian_residential_schools_gravesite_discoveries#Government" title="Canadian Indian residential schools gravesite discoveries">Canadian Indian residential schools gravesite discoveries § Government</a></div>
<p>As of June 2021, the government of <a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a> officially recognises eight genocides that took place beyond its borders: the <a href="https://en.wikipedia.org/wiki/Armenian_genocide" title="Armenian genocide">Armenian genocide</a> (1915–1917), the <a href="https://en.wikipedia.org/wiki/Holodomor" title="Holodomor">Holodomor</a> (1932–1933), <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">the Holocaust</a> (1941-1945), the <a href="https://en.wikipedia.org/wiki/Rwandan_genocide" title="Rwandan genocide">Rwandan genocide</a> (1994), the <a href="https://en.wikipedia.org/wiki/Srebrenica_massacre" title="Srebrenica massacre">Srebrenica massacre</a> (1995), the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genocide_of_Yazidis_by_ISIL" title="Genocide of Yazidis by ISIL">Genocide of Yazidis by ISIL</a> (2014), the <a href="https://en.wikipedia.org/wiki/Persecution_of_Uyghurs_in_China" title="Persecution of Uyghurs in China">Uyghur genocide</a> (2014–present; recognised by Canada in February 2021), and the <a href="https://en.wikipedia.org/wiki/Rohingya_genocide" title="Rohingya genocide">Rohingya genocide</a> (2016–present). Some activists and scholars such as <a href="https://en.wikipedia.org/wiki/Phil_Fontaine" title="Phil Fontaine">Phil Fontaine</a> and <a href="https://en.wikipedia.org/wiki/David_Bruce_MacDonald" title="David Bruce MacDonald">David Bruce MacDonald</a> have argued that the Canadian government should also officially recognise various atrocities committed against the <a href="https://en.wikipedia.org/wiki/Indigenous_peoples_in_Canada" title="Indigenous peoples in Canada">Indigenous peoples in Canada</a> from the late 19th century until the mid-20th century as 'genocide', especially after the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/2021_Canadian_Indian_residential_schools_gravesite_discoveries" title="2021 Canadian Indian residential schools gravesite discoveries">2021 Canadian Indian residential schools gravesite discoveries</a>.
In October 2022, the House of Commons unanimously passed a motion to
have the Canadian government officially recognize the residential school
system as genocide against Indigenous populations.
</p>
<h3><span class="mw-headline" id="Germany">Germany</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Wiedergutmachung" title="Wiedergutmachung">Wiedergutmachung</a>, <a href="https://en.wikipedia.org/wiki/Claims_Conference" title="Claims Conference">Claims Conference</a>, <a href="https://en.wikipedia.org/wiki/Reparations_Agreement_between_Israel_and_the_Federal_Republic_of_Germany" title="Reparations Agreement between Israel and the Federal Republic of Germany">Reparations Agreement between Israel and the Federal Republic of Germany</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Herero_and_Namaqua_genocide#Recognition" title="Herero and Namaqua genocide">Herero and Namaqua genocide § Recognition</a></div>
<p>Canadian political scientist <a href="https://en.wikipedia.org/wiki/David_Bruce_MacDonald" title="David Bruce MacDonald">David Bruce MacDonald</a>
stated in June 2021 that it is rare for governments to recognise
genocides committed by previous administrations of the same country,
citing <a href="https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a> as an example: it has officially recognised <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">the Holocaust</a> (committed by <a href="https://en.wikipedia.org/wiki/Nazi_Germany" title="Nazi Germany">Nazi Germany</a> during the Second World War), and in May 2021 Germany officially recognised the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Herero_and_Namaqua_genocide" title="Herero and Namaqua genocide">Herero and Namaqua genocide</a> (committed by the <a href="https://en.wikipedia.org/wiki/German_Empire" title="German Empire">German Empire</a> in 1904–1908).
</p>
<h3><span class="mw-headline" id="Israel">Israel</span></h3><p>On 21 November 2018, a bill tabled by opposition MP <a href="https://en.wikipedia.org/wiki/Ksenia_Svetlova" title="Ksenia Svetlova">Ksenia Svetlova</a> (<a href="https://en.wikipedia.org/wiki/Zionist_Union" title="Zionist Union">ZU</a>) to recognise the Islamic State's killing of Yazidis as a genocide was defeated in a 58 to 38 vote in the <a href="https://en.wikipedia.org/wiki/Knesset" title="Knesset">Knesset</a>. The <a href="https://en.wikipedia.org/wiki/Thirty-fourth_government_of_Israel" title="Thirty-fourth government of Israel">coalition parties</a> motivated their rejection of the bill by saying that the United Nations had not yet recognised it as a genocide.
</p>
<h3><span class="mw-headline" id="Netherlands">Netherlands</span></h3><p>In their 2017–2021 coalition agreement published on 10 October 2017, the four parties forming the <a href="https://en.wikipedia.org/wiki/Third_Rutte_cabinet" title="Third Rutte cabinet">Third Rutte cabinet</a>
stated the following policy: "For the Dutch government, rulings from
international courts of justice or criminal courts, unambiguous
conclusions from scientific research, and findings by the UN, are
leading in the recognition of genocides. The Netherlands act in
accordance with the obligations arising from the Convention on the
Prevention and Punishment of the Crime of Genocide. At the UN Security
Council, the Netherlands are pro-active in combating <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Islamic_State_in_Iraq_and_the_Levant" title="Islamic State in Iraq and the Levant">ISIS</a> and the prosecution of ISIS fighters." On 22 February 2018, the <a href="https://en.wikipedia.org/wiki/House_of_Representatives_(Netherlands)" title="House of Representatives (Netherlands)">Dutch House of Representatives</a> formally <a href="https://en.wikipedia.org/wiki/Armenian_genocide_recognition" title="Armenian genocide recognition">recognised the Armenian genocide</a> with 147 votes out of 150; only the three MPs of the <a href="https://en.wikipedia.org/wiki/Turks_in_the_Netherlands" title="Turks in the Netherlands">Dutch Turks</a>-dominated party <a class="mw-redirect" href="https://en.wikipedia.org/wiki/DENK_(political_party)" title="DENK (political party)">DENK</a> opposed recognition as a "too one-sided explanation of history".
Although the Dutch government stated it would not (yet) take a stand on
whether it was a genocide, instead using the phrase "the Armenian
genocide question", it agreed with MP <a href="https://en.wikipedia.org/wiki/Jo%C3%ABl_Voordewind" title="Joël Voordewind">Joël Voordewind</a>'s suggestion to send a government representative to attend <a href="https://en.wikipedia.org/wiki/Armenian_Genocide_Remembrance_Day" title="Armenian Genocide Remembrance Day">Armenian Genocide Remembrance Day</a> in <a href="https://en.wikipedia.org/wiki/Yerevan" title="Yerevan">Yerevan</a> every 5 years "to show respect to all victims and survivors of all massacres against minorities", said Foreign Minister <a href="https://en.wikipedia.org/wiki/Sigrid_Kaag" title="Sigrid Kaag">Sigrid Kaag</a>.
On 9 February 2021, a large majority of the House supported a motion
calling on the government to fully recognise the Armenian genocide and
dropping the phrase "the Armenian genocide question"; the only parties
who did not support the call were the <a href="https://en.wikipedia.org/wiki/People%27s_Party_for_Freedom_and_Democracy" title="People's Party for Freedom and Democracy">VVD</a>, and again DENK.
Inge Drost, spokesperson for the Federation Armenian Organisations
Netherlands, stated in April 2021: "Every time recognition was brought
up, it turned out to be a political bargaining tool. Then a country
wanted get something out of Turkey, and threatened to recognise the
Armenian genocide. Then eventually, it did not happen. It's a very
sensitive issue for us."
</p>
<h3><span class="mw-headline" id="United_Kingdom">United Kingdom</span></h3><p>The legal department of the British <a href="https://en.wikipedia.org/wiki/Foreign,_Commonwealth_and_Development_Office" title="Foreign, Commonwealth and Development Office">Foreign, Commonwealth and Development Office</a>
has a long-standing policy, dating back to the 1948 passing of the
Genocide Convention, of refusing to give a legal description to
potential war crimes. For this reason, it has sought to dissuade any UK
governmental institution from making claims about genocide. On 20 April
2016, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_the_United_Kingdom" title="House of Commons of the United Kingdom">House of Commons of the United Kingdom</a> unanimously supported a motion to declare that the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genocide_of_Yazidis_by_ISIL" title="Genocide of Yazidis by ISIL">treatment of Yazidis and Christians by the Islamic State amounted to genocide</a>,
to condemn it as such, and to refer the issue to the UN Security
Council. It was almost unprecedented for British parliamentarians to
collectively to declare war-time actions as genocide, because in doing
so, <a href="https://en.wikipedia.org/wiki/Conservative_Party_(UK)" title="Conservative Party (UK)">Conservative</a> MPs defied their fellow party members in the UK government. Foreign Office secretary <a href="https://en.wikipedia.org/wiki/Tobias_Ellwood" title="Tobias Ellwood">Tobias Ellwood</a>
– who was jeered at and interrupted by MPs during his speech in the
debate – stated that he personally believed genocide had taken place,
but that it was not up to politicians to make that determination, but to
the courts.
</p>
<h3><span class="mw-headline" id="United_States">United States</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/United_States_recognition_of_the_Armenian_genocide" title="United States recognition of the Armenian genocide">United States recognition of the Armenian genocide</a> and <a href="https://en.wikipedia.org/wiki/California_genocide#Apology_by_California's_governor" title="California genocide">California genocide § Apology by California's governor</a></div>
<p>Between 1989 and 2022, the <a href="https://en.wikipedia.org/wiki/United_States_Department_of_State" title="United States Department of State">United States Department of State</a>
has formally recognized eight genocides: in Bosnia (1993), Rwanda
(1994), Iraq (1995), Darfur (2004), and areas under the control of ISIS
(2016 and 2017). During the last days of the Trump administration the
Uyghur genocide was recognized, a decision affirmed by the Biden
administration, which also recognized the Armenian genocide in April
2021 and the Rohingya genocide in Burma/Myanmar, with the determination
coming in March 2022.
Three other cases were considered, namely Burundi in the mid-1990s,
Sudan's "Two Areas" in 2013, and Burma in 2018, but ultimately the
process of recognition was not completed. A March 2019 <a href="https://en.wikipedia.org/wiki/United_States_Holocaust_Memorial_Museum" title="United States Holocaust Memorial Museum">USHMM</a>
report by Buchwald & Keith stated: "No formal policy exists or has
existed to guide how or when the US government decides whether genocide
has occurred and whether to state its conclusion publicly." However, there are two memoranda – the first written by Secretary of State <a href="https://en.wikipedia.org/wiki/Warren_Christopher" title="Warren Christopher">Warren Christopher</a> in May 1994 regarding Rwanda, and the second by Secretary of State <a href="https://en.wikipedia.org/wiki/Colin_Powell" title="Colin Powell">Colin Powell</a>
in June 2004 regarding Darfur – that provide some insight into the
decision-making process, and advise or authoritise U.S. government
officials on what to do in genocide recognition questions.
</p>
<h2><span class="mw-headline" id="By_event">By event</span></h2><h3><span class="mw-headline" id="Pacification_of_Algeria">Pacification of Algeria</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<p>Some governments and scholars have called <a href="https://en.wikipedia.org/wiki/France" title="France">France</a>'s <a href="https://en.wikipedia.org/wiki/French_conquest_of_Algeria" title="French conquest of Algeria">conquest</a> of <a href="https://en.wikipedia.org/wiki/Algeria" title="Algeria">Algeria</a> a <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>, such as <a href="https://en.wikipedia.org/wiki/Raphael_Lemkin" title="Raphael Lemkin">Raphael Lemkin</a>, who coined the word "<a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>" in the 20th century and <a href="https://en.wikipedia.org/wiki/Ben_Kiernan" title="Ben Kiernan">Ben Kiernan</a>, an Australian expert on the <a href="https://en.wikipedia.org/wiki/Cambodian_genocide" title="Cambodian genocide">Cambodian genocide</a>, who wrote in <i><a href="https://en.wikipedia.org/wiki/Blood_and_Soil_(book)" title="Blood and Soil (book)">Blood and Soil: A World History of Genocide and Extermination from Sparta to Darfur</a></i> on the French conquest of <a href="https://en.wikipedia.org/wiki/Algeria" title="Algeria">Algeria</a>:
</p>
<blockquote>
<p><i>By 1875, the French conquest was complete. The war had killed
approximately 825,000 indigenous Algerians since 1830. A long shadow of
genocidal hatred persisted, provoking a French author to protest in 1882
that in Algeria, "we hear it repeated every day that we must expel the
native and if necessary destroy him." As a French statistical journal
urged five years late, "the system of extermination must give way to a
policy of penetration."</i><br /><i>- Ben Kiernan, Blood and Soil</i>
</p>
</blockquote></div></div>
<h3><span class="mw-headline" id="Anfal_campaign">Anfal campaign</span></h3><p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Kurdistan_Regional_Government" title="Kurdistan Regional Government">Kurdistan Regional Government</a> has set aside 14 April as a day of remembrance for the Al-Anfal campaign. In <a href="https://en.wikipedia.org/wiki/Sulaymaniyah" title="Sulaymaniyah">Sulaymanya</a> a museum was established in the <a href="https://en.wikipedia.org/wiki/Amna_Suraka" title="Amna Suraka">former prison</a> of the <a href="https://en.wikipedia.org/wiki/Directorate_of_General_Security" title="Directorate of General Security">Directorate of General Security</a>. Many <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Iraqi_Arabs" title="Iraqi Arabs">Iraqi Arabs</a> reject that any mass killings of Kurds occurred during the Anfal campaign.
</p><p>On 28 February 2013, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/British_House_of_Commons" title="British House of Commons">British House of Commons</a> formally recognized the Anfal as genocide following a campaign led by Conservative MP <a href="https://en.wikipedia.org/wiki/Nadhim_Zahawi" title="Nadhim Zahawi">Nadhim Zahawi</a>, who is of <a href="https://en.wikipedia.org/wiki/Kurds_in_the_United_Kingdom" title="Kurds in the United Kingdom">Kurdish descent</a>.
</p>
<h3><span class="mw-headline" id="Armenian_genocide">Armenian genocide</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:The_Eternal_Flame_-_Armenian_Genocide_Memorial_in_Yerevan.jpg"><img class="mw-file-element" data-file-height="3456" data-file-width="5184" height="267" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/36/The_Eternal_Flame_-_Armenian_Genocide_Memorial_in_Yerevan.jpg/300px-The_Eternal_Flame_-_Armenian_Genocide_Memorial_in_Yerevan.jpg" width="400" /></a><figcaption>The eternal flame at the center of the twelve slabs, located at the <a href="https://en.wikipedia.org/wiki/Tsitsernakaberd" title="Tsitsernakaberd">Armenian Genocide Memorial complex</a> in <a href="https://en.wikipedia.org/wiki/Yerevan" title="Yerevan">Yerevan</a>, Armenia</figcaption></figure>
<p><a href="https://en.wikipedia.org/wiki/Armenian_genocide_recognition" title="Armenian genocide recognition">Armenian genocide recognition</a> is the formal acceptance that the <a href="https://en.wikipedia.org/wiki/Armenian_genocide" title="Armenian genocide">systematic massacres and forced deportation</a> of <a href="https://en.wikipedia.org/wiki/Armenians" title="Armenians">Armenians</a> committed by the <a href="https://en.wikipedia.org/wiki/Ottoman_Empire" title="Ottoman Empire">Ottoman Empire</a> from 1915 to 1923, during and after the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/First_World_War" title="First World War">First World War</a>, constituted <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>.
</p><p>Most historians outside Turkey recognize the fact that the Ottoman persecution of Armenians was a genocide. However, despite the recognition of the genocidal character of the
massacre of Armenians in scholarship as well as in civil society, some
governments have been reticent to officially acknowledge the killings as
genocide because of political concerns about their relations with the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Republic_of_Turkey" title="Republic of Turkey">Republic of Turkey</a>.
</p>
As of 2023, governments and parliaments of 34 countries, including
Argentina, Brazil, Canada, France, Germany, Italy, Mexico, the
Netherlands, Portugal, Russia, Sweden and the United States, have
formally recognized the Armenian genocide. Three countries — Azerbaijan,
Turkey, and Pakistan — deny that there was an Armenian genocide.</div></div>
<h3><span class="mw-headline" id="Anti-Sikh_riots">Anti-Sikh riots</span></h3><p>The <a href="https://en.wikipedia.org/wiki/1984_anti-Sikh_riots" title="1984 anti-Sikh riots">1984 anti-Sikh riots</a>, also known as the <i>1984 Sikh Massacre</i>, was a series of organised <a href="https://en.wikipedia.org/wiki/Pogrom" title="Pogrom">pogroms</a><sup> </sup>against <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sikh" title="Sikh">Sikhs</a> in <a href="https://en.wikipedia.org/wiki/India" title="India">India</a> following the <a href="https://en.wikipedia.org/wiki/Assassination_of_Indira_Gandhi" title="Assassination of Indira Gandhi">assassination of Indira Gandhi</a> by her Sikh bodyguards. The ruling <a href="https://en.wikipedia.org/wiki/Indian_National_Congress" title="Indian National Congress">Indian National Congress</a> had been in active complicity with the mob, as to the organisation of the riots. Government estimates project that about 2,800 Sikhs were killed in <a href="https://en.wikipedia.org/wiki/Delhi" title="Delhi">Delhi</a><sup> </sup>and 3,350 nationwide independent sources estimate the number of deaths at about 8,000–17,000.
</p>
<div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<p>On 12 August 2005, <a href="https://en.wikipedia.org/wiki/Manmohan_Singh" title="Manmohan Singh">Manmohan Singh</a> apologised in the <a href="https://en.wikipedia.org/wiki/Lok_Sabha" title="Lok Sabha">Lok Sabha</a> for the riots. The riots are cited as a reason to support the creation of a Sikh homeland in India, often called <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Khalistan" title="Khalistan">Khalistan</a>.
</p><p>Many Indians of different religions made significant efforts to hide and help Sikh families during the rioting. The Sikh <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jathedar_of_Akal_Takht" title="Jathedar of Akal Takht">Jathedar of Akal Takht</a> declared the events following the death of Indira Gandhi a Sikh "<a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>", replacing "anti-Sikh riots" widely used by the Indian government, the media and writers, on 15 July 2010. The decision came soon after a similar motion was raised in the Canadian Parliament by <a href="https://en.wikipedia.org/wiki/Sukh_Dhaliwal" title="Sukh Dhaliwal">Sukh Dhaliwal</a>, a Sikh <a href="https://en.wikipedia.org/wiki/Member_of_Parliament_(Canada)" title="Member of Parliament (Canada)">MP</a>.
</p><p>On 16 April 2015, Assembly Concurrent Resolution 34 (ACR 34) was passed by the <a href="https://en.wikipedia.org/wiki/California_State_Assembly" title="California State Assembly">California State Assembly</a>.
Co-authored by Sacramento-area assembly members Jim Cooper, Kevin
McCarty, Jim Gallagher and Ken Cooley, the resolution criticized the
Government for participating in and failing to prevent the killings. The
assembly called the killings a "genocide", as it "resulted in the
intentional destruction of many Sikh families, communities, homes and
businesses." In April 2017, the <a href="https://en.wikipedia.org/wiki/Legislative_Assembly_of_Ontario" title="Legislative Assembly of Ontario">Ontario Legislature</a> passed a motion condemning the anti-Sikh riots as "genocide". The Indian government lobbied against the motion and condemned it upon its adoption.
In February 2018, American state of Connecticut, passed a bill stating,
30 November of each year to be "Sikh Genocide" Remembrance Day to
remember the lives lost on 30 November 1984, during the Sikh Genocide.
</p>
On 15 January 2017, the <a href="https://en.wikipedia.org/wiki/Wall_of_Truth" title="Wall of Truth">Wall of Truth</a> was inaugurated in <a href="https://en.wikipedia.org/wiki/Lutyens%27_Delhi" title="Lutyens' Delhi">Lutyens' Delhi</a>, New Delhi, as a memorial for Sikhs killed during the 1984 riots (and other hate crimes across the world).</div></div>
<h3><span id="Assyrian_genocide_.28Sayfo.29"></span><span class="mw-headline" id="Assyrian_genocide_(Sayfo)">Assyrian genocide (Sayfo)</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
During the 1990s, before the first academic research on the Sayfo, Assyrian diaspora groups (inspired by campaigns for <a href="https://en.wikipedia.org/wiki/Armenian_genocide_recognition" title="Armenian genocide recognition">Armenian genocide recognition</a>) began to press for a similar formal acknowledgement. In parallel with the political campaign, Armenian genocide research began to include Assyrians as victims. In December 2007, the <a href="https://en.wikipedia.org/wiki/International_Association_of_Genocide_Scholars" title="International Association of Genocide Scholars">International Association of Genocide Scholars</a> passed a resolution recognizing the Assyrian genocide. The Sayfo is also recognized as a genocide in resolutions passed by Sweden (in 2010), Armenia (2015), the Netherlands (2015), and Germany (in 2016).<sup> </sup>Memorials in Armenia, Australia, Belgium, France, Greece, Sweden,
Ukraine, and the United States commemorate victims of the Sayfo.</div></div>
<h3><span class="mw-headline" id="Atrocities_in_the_Congo_Free_State">Atrocities in the Congo Free State</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Belgian_apologies_to_the_Congo" title="Belgian apologies to the Congo">Belgian apologies to the Congo</a><br /><div class="excerpt">
<div class="quotebox pullquote floatright" style="width: 25em;">
<blockquote class="quotebox-quote left-aligned">
<p>... It was indeed a holocaust before Hitler's Holocaust. ... What
happened in the heart of Africa was genocidal in scope long before that
now familiar term, genocide, was ever coined.
</p>
</blockquote>
<p style="padding-bottom: 0em;"><cite class="left-aligned">Historian <a href="https://en.wikipedia.org/wiki/Robert_Weisbord" title="Robert Weisbord">Robert Weisbord</a> (2003)</cite></p>
</div>
<p>The significant number of deaths under the Free State regime has led some scholars to relate the atrocities to later <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocides</a>,
though understanding of the losses under the colonial administration's
rule as the result of harsh economic exploitation rather than a policy
of deliberate extermination has led others to dispute the comparison; there is an open debate as to whether the atrocities constitute genocide. According to the <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a>' <a href="https://en.wikipedia.org/wiki/Genocide_Convention#Definition_of_genocide" title="Genocide Convention">1948 definition of the term "genocide"</a>, a genocide must be "acts committed with <a href="https://en.wikipedia.org/wiki/Genocidal_intent" title="Genocidal intent">intent to destroy</a>, in whole or in part, a national, ethnical, racial or religious group".
According to Georgi Verbeeck, this conventional definition of genocide
has prevented most historians from using the term to describe atrocities
in the Free State; in the strict sense of the term, most historians
have rejected allegations of genocide.
</p><p>Sociologist <a href="https://en.wikipedia.org/wiki/Rhoda_Howard-Hassmann" title="Rhoda Howard-Hassmann">Rhoda Howard-Hassmann</a>
stated that because the Congolese were not killed in a systematic
fashion according to this criterion, "technically speaking, this was not
genocide even in a legally retroactive sense." Hochschild and political scientist <a href="https://en.wikipedia.org/wiki/Georges_Nzongola-Ntalaja" title="Georges Nzongola-Ntalaja">Georges Nzongola-Ntalaja</a>
rejected allegations of genocide in the Free State because there was no
evidence of a policy of deliberate extermination or the desire to
eliminate any specific population groups though the latter added that nevertheless there was "a death toll of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Holocaust" title="Holocaust">Holocaust</a> proportions," which led him to call it "the Congo holocaust."
</p>
<div class="quotebox pullquote floatleft" style="width: 25em;">
<blockquote class="quotebox-quote left-aligned">
<p>... no reputable historian of the Congo has made charges of genocide;
a forced labor system, although it may be equally deadly, is different.
</p>
</blockquote>
<p style="padding-bottom: 0em;"><cite class="left-aligned">Historian <a href="https://en.wikipedia.org/wiki/Adam_Hochschild" title="Adam Hochschild">Adam Hochschild</a> (2005)</cite></p>
</div>
<p>It is generally agreed by historians that extermination was never the
policy of the Free State. According to Van Reybrouck, "It would be
absurd ... to speak of an act of 'genocide' or a 'holocaust'; genocide
implies the conscious, planned annihilation of a specific population,
and that was never the intention here, or the result ... But it was
definitely a <a href="https://en.wikipedia.org/wiki/Hecatomb" title="Hecatomb">hecatomb</a>,
a slaughter on a staggering scale that was not intentional, but could
have been recognised much earlier as the collateral damage of a
perfidious, rapacious policy of exploitation". Historian <a href="https://en.wikipedia.org/wiki/Barbara_Emerson" title="Barbara Emerson">Barbara Emerson</a>
stated, "Leopold did not start genocide. He was greedy for money and
chose not to interest himself when things got out of control."
According to Hochschild, "while not a case of genocide, in the strict
sense", the atrocities in the Congo were "one of the most appalling
slaughters known to have been brought about by human agency".
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Hands_of_Lingomo_and_Bolengo.tif"><img class="mw-file-element" data-file-height="875" data-file-width="1125" height="311" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Hands_of_Lingomo_and_Bolengo.tif/lossless-page1-220px-Hands_of_Lingomo_and_Bolengo.tif.png" width="400" /></a><figcaption>Picture of "Congolese men holding cut off hands" captured by <a href="https://en.wikipedia.org/wiki/Alice_Seeley_Harris" title="Alice Seeley Harris">Alice Seeley Harris</a> in <a href="https://en.wikipedia.org/wiki/Baringa,_Democratic_Republic_of_the_Congo" title="Baringa, Democratic Republic of the Congo">Baringa</a>, May 1904</figcaption></figure>
<p>Historians have argued that comparisons drawn in the press by some
between the death toll of the Free State atrocities and the Holocaust
during <a href="https://en.wikipedia.org/wiki/World_War_II" title="World War II">World War II</a> have been responsible for creating undue confusion over the issue of terminology. In one incident, the Japanese newspaper <i><a href="https://en.wikipedia.org/wiki/Yomiuri_Shimbun" title="Yomiuri Shimbun">Yomiuri Shimbun</a></i>
used the word "genocide" in the title of a 2005 article by Hochschild.
Hochschild himself criticised the title as "misleading" and stated that
it had been chosen "without my knowledge". Similar criticism was echoed
by historian <a class="new" href="https://en.wikipedia.org/w/index.php?title=Jean-Luc_Vellut&action=edit&redlink=1" title="Jean-Luc Vellut (page does not exist)">Jean-Luc Vellut</a>. Allegations of genocide in the Free State have become common over time. Political scientist Martin Ewans wrote, "Leopold's African regime became a byword for exploitation and genocide." According to historian <a class="new" href="https://en.wikipedia.org/w/index.php?title=Timothy_J._Stapleton&action=edit&redlink=1" title="Timothy J. Stapleton (page does not exist)">Timothy J. Stapleton</a>,
"Those who easily apply the term genocide to Leopold's regime seem to
do so purely on the basis of its obvious horror and the massive numbers
of people who may have perished." <a href="https://en.wikipedia.org/wiki/Robert_Weisbord" title="Robert Weisbord">Robert Weisbord</a> argued that there does not have to be intent to exterminate all members of a population in a genocide.
He posited that "an endeavor to eliminate a portion of a people would
qualify as genocide" according to the UN standards and asserted that the
Free State did as much. Jeanne Haskin, Yaa-Lengi Meema Ngemi, and <a href="https://en.wikipedia.org/wiki/David_Olusoga" title="David Olusoga">David Olusoga</a> also referred to the atrocities as a genocide. In an unpublished manuscript from the 1950s, Lemkin, who had first
coined the term "genocide" in 1944, asserted the occurrence of "an
unambiguous genocide" in the Free State, though he blamed the violence
on what he saw as "the savagery of African colonial troops". Lemkin emphasized that the atrocities were usually committed by Africans themselves who were in the pay of the Belgians.
These "native militia" were described by Lemkin as "an unorganized and
disorderly rabble of savages whose only recompense was what they
obtained from looting, and when they were cannibals, as was usually the
case, in eating the foes against whom they were sent". Genocide scholar <a href="https://en.wikipedia.org/wiki/Adam_Jones_(Canadian_scholar)" title="Adam Jones (Canadian scholar)">Adam Jones</a>
claimed that the underrepresentation of males in Congolese population
figures after Leopold's rule is evidence that "outright genocide" was
the cause of a large portion of deaths in the Free State.
</p><p>In 1999 Hochschild published <i><a href="https://en.wikipedia.org/wiki/King_Leopold%27s_Ghost" title="King Leopold's Ghost">King Leopold's Ghost</a></i>,
a book detailing the atrocities committed during the Free State's
existence. The book became a bestseller in Belgium, but aroused
criticism from former Belgian colonialists and some academics as
exaggerating the extent of the atrocities and population decline.
Around the 50th anniversary of the Congo's independence from Belgium in
2010, numerous Belgian writers published content about the Congo.
Historian Idesbald Goddeeris criticised these works—including Van
Reybrouk's <i>Congo: A History</i>—for taking a softened stance on the
atrocities committed in the Congolese Free State, saying "They
acknowledge the dark period of the Congo Free State, but...they
emphasize that the number of victims was unknown and that the terror was
concentrated in particular regions."
</p>
The term "Congolese genocide" is often used in an unrelated sense to
refer to the mass murder and rape committed in the eastern Congo in the
aftermath of the <a href="https://en.wikipedia.org/wiki/Rwandan_genocide" title="Rwandan genocide">Rwandan genocide</a> (and the ensuing <a href="https://en.wikipedia.org/wiki/Second_Congo_War" title="Second Congo War">Second Congo War</a>) between 1998 and 2003.</div></div>
<h3><span class="mw-headline" id="Black_War">Black War</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<p>The near-destruction of Tasmania's Aboriginal population has been described as an act of genocide by historians including <a href="https://en.wikipedia.org/wiki/Robert_Hughes_(critic)" title="Robert Hughes (critic)">Robert Hughes</a>, James Boyce, <a href="https://en.wikipedia.org/wiki/Lyndall_Ryan" title="Lyndall Ryan">Lyndall Ryan</a>, Tom Lawson, <a href="https://en.wikipedia.org/wiki/Mohamed_Adhikari" title="Mohamed Adhikari">Mohamed Adhikari</a>, Benjamin Madley, and Ashley Riley Sousa. The author of the concept of genocide, <a href="https://en.wikipedia.org/wiki/Raphael_Lemkin" title="Raphael Lemkin">Raphael Lemkin</a>, considered Tasmania the site of one of the world's clear cases of genocide and Hughes has described the loss of Aboriginal Tasmanians as "the only true genocide in English colonial history". However, other historians including <a href="https://en.wikipedia.org/wiki/Henry_Reynolds_(historian)" title="Henry Reynolds (historian)">Henry Reynolds</a>, <a href="https://en.wikipedia.org/wiki/Richard_Broome" title="Richard Broome">Richard Broome</a>,
and Nicholas Clements do not agree with the genocide thesis, arguing
that the colonial authorities did not intend to destroy the Aboriginal
population in whole or in part.
</p><p>Boyce has claimed that the April 1828 "Proclamation Separating
the Aborigines from the White Inhabitants" sanctioned force against
Aboriginal people "for no other reason than that they were Aboriginal".
However, as Reynolds, Broome and Clements point out, there was open
warfare at the time<a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-Black_War_:1-110">.</a>
Boyce describes the decision to remove all Aboriginal Tasmanians after
1832—by which time they had given up their fight against white
colonists—as an extreme policy position. He concludes: "The colonial
government from 1832 to 1838 <a href="https://en.wikipedia.org/wiki/Ethnic_cleansing" title="Ethnic cleansing">ethnically cleansed</a> the western half of Van Diemen's Land and then callously left the exiled people to their fate."
</p><p>As early as 1852 <a href="https://en.wikipedia.org/wiki/John_West_(writer)" title="John West (writer)">John West</a>'s <i>History of Tasmania</i> portrayed the obliteration of Tasmania's Aboriginal people as an example of "systematic massacre" and in the 1979 <a href="https://en.wikipedia.org/wiki/High_Court_of_Australia" title="High Court of Australia">High Court</a> case of <a href="https://en.wikipedia.org/wiki/Paul_Coe" title="Paul Coe">Coe v Commonwealth of Australia</a>, judge <a href="https://en.wikipedia.org/wiki/Lionel_Murphy" title="Lionel Murphy">Lionel Murphy</a>
observed that Aboriginal people did not give up their land peacefully
and that they were killed or forcibly removed from their land "in what
amounted to attempted (and in Tasmania almost complete) genocide".
</p><p>Historian <a href="https://en.wikipedia.org/wiki/Henry_Reynolds_(historian)" title="Henry Reynolds (historian)">Henry Reynolds</a>
says there was a widespread call from settlers during the frontier wars
for the "extirpation" or "extermination" of the Aboriginal people.
But he has contended that the British government acted as a source of
restraint on settlers' actions. Reynolds says there is no evidence the
British government deliberately planned the wholesale destruction of
indigenous Tasmanians—a November 1830 letter to Arthur by Sir George
Murray warned that the extinction of the race would leave "an indelible
stain upon the character of the British Government"—and therefore what eventuated does not meet the definition of genocide codified in the 1948 <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">United Nations convention</a>.
He says Arthur was determined to defeat the Aboriginal people and take
their land, but believes there is little evidence he had aims beyond
that objective and wished to destroy the Tasmanian race.
In contrast to Reynolds' argument, historian Lyndall Ryan, based on a
sample of massacres taking place in the Meander River region in June
1827, concludes that massacres of Aboriginal Tasmanians by white
settlers were likely part of an organised process and were sanctioned by
government authorities.
</p><p>Clements accepts Reynolds' argument but also exonerates the
colonists themselves of the charge of genocide. He says that unlike
genocidal determinations by <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">Nazis against Jews</a> in World War II, <a href="https://en.wikipedia.org/wiki/Rwandan_genocide" title="Rwandan genocide">Hutus against Tutsis</a> in <a href="https://en.wikipedia.org/wiki/Rwanda" title="Rwanda">Rwanda</a> and <a href="https://en.wikipedia.org/wiki/Armenian_genocide" title="Armenian genocide">Ottomans against Armenians</a> in present-day <a href="https://en.wikipedia.org/wiki/Turkey" title="Turkey">Turkey</a>,
which were carried out for ideological reasons, Tasmanian settlers
participated in violence largely out of revenge and self-preservation.
He adds: "Even those who were motivated by sex or morbid thrillseeking
lacked any ideological impetus to exterminate the natives." He also
argues that while genocides are inflicted on defeated, captive or
otherwise vulnerable minorities, Tasmanian natives appeared as a
"capable and terrifying enemy" to colonists and were killed in the
context of a war in which both sides killed noncombatants.
</p>
Lawson, in a critique of Reynolds' stand, argues that genocide was the
inevitable outcome of a set of British policies to colonise Van Diemen's
Land.
He says the British government endorsed the use of partitioning and
"absolute force" against Tasmanians, approved Robinson's "Friendly
Mission" and colluded in transforming that mission into a campaign of
ethnic cleansing from 1832. He says that once on Flinders Island,
indigenous peoples were taught to farm land like Europeans and worship
God like Europeans and concludes: "The campaign of transformation
enacted on Flinders Island amounted to cultural genocide."</div></div>
<h3><span class="mw-headline" id="Bosnian_genocide">Bosnian genocide</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Memorijalni_centar_Srebrenica-Poto%C4%8Dari6.JPG"><img class="mw-file-element" data-file-height="3000" data-file-width="4000" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Memorijalni_centar_Srebrenica-Poto%C4%8Dari6.JPG/220px-Memorijalni_centar_Srebrenica-Poto%C4%8Dari6.JPG" width="400" /></a><figcaption>Memorial stone at the <a href="https://en.wikipedia.org/wiki/Srebrenica_Genocide_Memorial" title="Srebrenica Genocide Memorial">Srebrenica-Potočari Memorial Centre</a></figcaption></figure>
<div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/Bosnian_genocide" title="Bosnian genocide">Bosnian genocide</a></div>
<div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Bosnian_genocide_denial" title="Bosnian genocide denial">Bosnian genocide denial</a></div>
<p>The term "<a href="https://en.wikipedia.org/wiki/Bosnian_genocide" title="Bosnian genocide">Bosnian genocide</a>" refers to either the <a href="https://en.wikipedia.org/wiki/Srebrenica_massacre" title="Srebrenica massacre">Srebrenica massacre</a>, or the wider <a href="https://en.wikipedia.org/wiki/Crimes_against_humanity" title="Crimes against humanity">crimes against humanity</a> and <a href="https://en.wikipedia.org/wiki/Ethnic_cleansing_in_the_Bosnian_War" title="Ethnic cleansing in the Bosnian War">ethnic cleansing</a> campaign which was waged throughout the areas of <a href="https://en.wikipedia.org/wiki/Bosnia_and_Herzegovina" title="Bosnia and Herzegovina">Bosnia and Herzegovina</a> which were controlled by the <a href="https://en.wikipedia.org/wiki/Army_of_Republika_Srpska" title="Army of Republika Srpska">Army of Republika Srpska</a> (VRS) during the <a href="https://en.wikipedia.org/wiki/Bosnian_War" title="Bosnian War">Bosnian War</a> of 1992–1995. The events in Srebrenica in 1995 included the killing of more than 8,000 <a href="https://en.wikipedia.org/wiki/Bosniaks" title="Bosniaks">Bosniak</a> (<a href="https://en.wikipedia.org/wiki/Muslims_(ethnic_group)" title="Muslims (ethnic group)">Bosnian Muslim</a>)
men and boys, as well as the mass expulsion of another 25,000–30,000
Bosniak civilians by VRS units under the command of General <a href="https://en.wikipedia.org/wiki/Ratko_Mladi%C4%87" title="Ratko Mladić">Ratko Mladić</a>.
</p><p>In the 1990s, several authorities asserted that the ethnic
cleansing campaign which was carried out by elements of the Bosnian Serb
army was a <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>. These included a resolution by the <a href="https://en.wikipedia.org/wiki/United_Nations_General_Assembly" title="United Nations General Assembly">United Nations General Assembly</a>
and three convictions for genocide in German courts (the convictions
were based upon a wider interpretation of genocide than that used by <a href="https://en.wikipedia.org/wiki/International_court" title="International court">international courts</a>). In 2005, the <a href="https://en.wikipedia.org/wiki/United_States_Congress" title="United States Congress">United States Congress</a> passed a resolution declaring that "the Serbian policies of aggression and ethnic cleansing meet the terms defining genocide."
</p><p>The <a href="https://en.wikipedia.org/wiki/Srebrenica_massacre" title="Srebrenica massacre">Srebrenica massacre</a> was found to be an act of genocide by the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/International_Criminal_Tribunal_for_the_Former_Yugoslavia" title="International Criminal Tribunal for the Former Yugoslavia">International Criminal Tribunal for the Former Yugoslavia</a> (ICTY), a finding which was upheld by the <a href="https://en.wikipedia.org/wiki/International_Court_of_Justice" title="International Court of Justice">International Court of Justice</a> (ICJ). On 24 March 2016, former Bosnian Serb leader and the first president of the <a href="https://en.wikipedia.org/wiki/Republika_Srpska" title="Republika Srpska">Republika Srpska</a>, <a href="https://en.wikipedia.org/wiki/Radovan_Karad%C5%BEi%C4%87" title="Radovan Karadžić">Radovan Karadžić</a>, was found guilty of <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a> in <a href="https://en.wikipedia.org/wiki/Srebrenica" title="Srebrenica">Srebrenica</a>, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/War_crimes" title="War crimes">war crimes</a>, and <a href="https://en.wikipedia.org/wiki/Crimes_against_humanity" title="Crimes against humanity">crimes against humanity</a> and sentenced to 40 years in prison. In 2019 an appeals court increased his sentence to <a href="https://en.wikipedia.org/wiki/Life_imprisonment" title="Life imprisonment">life imprisonment</a>.
The ICTY found the acts to have satisfied the requirements for "guilty
acts" of genocide, and that, "some physical perpetrators held the intent
to physically destroy the protected groups of Bosnian Muslims and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bosnian_Croats" title="Bosnian Croats">Croats</a>".
</p>
<h3><span class="mw-headline" id="California_genocide">California genocide</span></h3><div class="excerpt-block"><div class="excerpt">
<p>In a speech before representatives of Native American peoples in June, 2019, California governor <a href="https://en.wikipedia.org/wiki/Gavin_Newsom" title="Gavin Newsom">Gavin Newsom</a> apologized for the genocide. Newsom referring to the proposed <i>California Truth and Healing Council</i>
said, "California must reckon with our dark history. California Native
American peoples suffered violence, discrimination and exploitation
sanctioned by state government throughout its history .... It's called
genocide. That's what it was, a genocide. No other way to describe it.
And that's the way it needs to be described in the history books. We can
never undo the wrongs inflicted on the peoples who have lived on this
land that we now call California since time immemorial, but we can work
together to build bridges, tell the truth about our past and begin to
heal deep wounds."
After hearing testimony, a Truth and Healing Council will clarify the
historical record on the relationship between the state and California
Native Americans.
</p>
In November 2021, the board of directors of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/University_of_California_Hastings_College_of_Law" title="University of California Hastings College of Law">University of California Hastings College of Law</a> voted to change the name of the institution because of namesake <a href="https://en.wikipedia.org/wiki/Serranus_Clinton_Hastings" title="Serranus Clinton Hastings">S. C. Hastings</a>' involvement in the killing and dispossessing of <a href="https://en.wikipedia.org/wiki/Yuki_people" title="Yuki people">Yuki people</a> in the 1850s.</div></div>
<h3><span class="mw-headline" id="Circassian_genocide">Circassian genocide</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
On 21 May 2011, the <a href="https://en.wikipedia.org/wiki/Parliament_of_Georgia" title="Parliament of Georgia">Parliament of Georgia</a>
passed a resolution stating that pre-planned mass killings of
Circassians by Imperial Russia, accompanied by "deliberate famine and
epidemics", should be recognized as "genocide", and that those deported
during those events from their homeland should be recognized as
"refugees". Georgia has made outreach efforts to North Caucasian ethnic
groups since the 2008 <a href="https://en.wikipedia.org/wiki/Russo-Georgian_War" title="Russo-Georgian War">Russo-Georgian War</a>. Following a <a href="https://en.wikipedia.org/wiki/Hidden_Nations,_Enduring_Crimes_conference" title="Hidden Nations, Enduring Crimes conference">consultation with academics, human rights activists and Circassian diaspora groups</a>
and parliamentary discussions in Tbilisi in 2010 and 2011, Georgia
became the first country to use the word "genocide" to refer to the
events. On 20 May 2011 the parliament of the Republic of Georgia declared in its resolution that the mass annihilation of the Cherkess (Adyghe) people during the Russian-Caucasian war and thereafter constituted <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a> as defined in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hague_Convention_of_1907" title="Hague Convention of 1907">Hague Convention of 1907</a> and the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/UN_Convention_of_1948" title="UN Convention of 1948">UN Convention of 1948</a>. The next year, on the same day of 21 May, a monument was erected in <a href="https://en.wikipedia.org/wiki/Anaklia" title="Anaklia">Anaklia</a>, <a href="https://en.wikipedia.org/wiki/Georgia_(country)" title="Georgia (country)">Georgia</a>, to commemorate the suffering of the Circassians.</div></div>
<h3><span class="mw-headline" id="Deportation_of_the_Chechens_and_Ingush">Deportation of the Chechens and Ingush</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
<figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:%D0%9C%D0%B8%D1%82%D0%B8%D0%BD%D0%B3_%D0%B2_%D0%A1%D1%82%D1%80%D0%B0%D1%81%D0%B1%D1%83%D1%80%D0%B3%D0%B5_%D0%B2_%D0%BF%D0%B0%D0%BC%D1%8F%D1%82%D1%8C_%D0%B4%D0%B5%D0%BF%D0%BE%D1%80%D1%82%D0%B0%D1%86%D0%B8%D0%B8_%D1%87%D0%B5%D1%87%D0%B5%D0%BD%D1%86%D0%B5%D0%B2_%D0%B8_%D0%B8%D0%BD%D0%B3%D1%83%D1%88%D0%B5%D0%B9_(10).jpg"><img class="mw-file-element" data-file-height="720" data-file-width="960" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/94/%D0%9C%D0%B8%D1%82%D0%B8%D0%BD%D0%B3_%D0%B2_%D0%A1%D1%82%D1%80%D0%B0%D1%81%D0%B1%D1%83%D1%80%D0%B3%D0%B5_%D0%B2_%D0%BF%D0%B0%D0%BC%D1%8F%D1%82%D1%8C_%D0%B4%D0%B5%D0%BF%D0%BE%D1%80%D1%82%D0%B0%D1%86%D0%B8%D0%B8_%D1%87%D0%B5%D1%87%D0%B5%D0%BD%D1%86%D0%B5%D0%B2_%D0%B8_%D0%B8%D0%BD%D0%B3%D1%83%D1%88%D0%B5%D0%B9_%2810%29.jpg/220px-%D0%9C%D0%B8%D1%82%D0%B8%D0%BD%D0%B3_%D0%B2_%D0%A1%D1%82%D1%80%D0%B0%D1%81%D0%B1%D1%83%D1%80%D0%B3%D0%B5_%D0%B2_%D0%BF%D0%B0%D0%BC%D1%8F%D1%82%D1%8C_%D0%B4%D0%B5%D0%BF%D0%BE%D1%80%D1%82%D0%B0%D1%86%D0%B8%D0%B8_%D1%87%D0%B5%D1%87%D0%B5%D0%BD%D1%86%D0%B5%D0%B2_%D0%B8_%D0%B8%D0%BD%D0%B3%D1%83%D1%88%D0%B5%D0%B9_%2810%29.jpg" width="400" /></a><figcaption>Meeting in Strasbourg on February 23, 2017 dedicated to the anniversary of deportation</figcaption></figure>
<p>The forced relocation, slaughter, and conditions during and after transfer have been described as an act of <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a> by various scholars as well as the European Parliament on the basis of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hague_Conventions_(1899_and_1907)" title="Hague Conventions (1899 and 1907)">IV Hague Convention of 1907</a> and the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Convention on the Prevention and Punishment of the Crime of Genocide</a> of the <a href="https://en.wikipedia.org/wiki/United_Nations_General_Assembly" title="United Nations General Assembly">U.N. General Assembly</a> (adopted in 1948), including French historian and expert on communist studies <a href="https://en.wikipedia.org/wiki/Nicolas_Werth" title="Nicolas Werth">Nicolas Werth</a>, German historian Philipp Ther, Professor Anthony James Joes, American journalist <a href="https://en.wikipedia.org/wiki/Eric_Margolis_(journalist)" title="Eric Margolis (journalist)">Eric Margolis</a>, Canadian political scientist <a href="https://en.wikipedia.org/wiki/Adam_Jones_(Canadian_scholar)" title="Adam Jones (Canadian scholar)">Adam Jones</a>, professor of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Islamic_History" title="Islamic History">Islamic History</a> at the <a href="https://en.wikipedia.org/wiki/University_of_Massachusetts_Dartmouth" title="University of Massachusetts Dartmouth">University of Massachusetts Dartmouth</a> <a href="https://en.wikipedia.org/wiki/Brian_Glyn_Williams" title="Brian Glyn Williams">Brian Glyn Williams</a>, scholars Michael Fredholm and Fanny E. Bryan. <a href="https://en.wikipedia.org/wiki/Raphael_Lemkin" title="Raphael Lemkin">Raphael Lemkin</a>, a <a href="https://en.wikipedia.org/wiki/Lawyer" title="Lawyer">lawyer</a> of <a href="https://en.wikipedia.org/wiki/Poland" title="Poland">Polish</a>-<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Jewish" title="Jewish">Jewish</a>
descent who initiated the Genocide Convention, assumed that genocide
was perpetrated in the context of the mass deportation of the Chechens,
Ingush, Volga Germans, Crimean Tatars, Kalmyks and Karachay. German investigative journalist <a href="https://en.wikipedia.org/wiki/Lutz_Kleveman" title="Lutz Kleveman">Lutz Kleveman</a> compared the deportation to a "slow genocide". In this case this was acknowledged by the <a href="https://en.wikipedia.org/wiki/European_Parliament" title="European Parliament">European Parliament</a> as an act of genocide in 2004:
</p>
<blockquote class="templatequote"><p>...Believes that the deportation of
the entire Chechen people to Central Asia on 23 February 1944 on the
orders of Stalin constitutes an act of genocide within the meaning of
the Fourth Hague Convention of 1907 and the Convention for the
Prevention and Repression of the Crime of Genocide adopted by the UN
General Assembly on 9 December 1948.</p></blockquote>
<p>On 26 April 1991 the Supreme Soviet of the Russian Socialist Federal Soviet Republic, under its chairman <a href="https://en.wikipedia.org/wiki/Boris_Yeltsin" title="Boris Yeltsin">Boris Yeltsin</a>,
passed the law On the Rehabilitation of Repressed Peoples with Article 2
denouncing all mass deportations as "Stalin's policy of defamation and <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>." Experts of the <a href="https://en.wikipedia.org/wiki/United_States_Holocaust_Memorial_Museum" title="United States Holocaust Memorial Museum">United States Holocaust Memorial Museum</a> cited the events of 1944 for a reason of placing Chechnya on their genocide watch list for its potential for genocide. The <a href="https://en.wikipedia.org/wiki/Chechen_Republic_of_Ichkeria" title="Chechen Republic of Ichkeria">separatist government of Chechnya</a> also recognized it as genocide. Members of the <a href="https://en.wikipedia.org/wiki/Chechen_diaspora" title="Chechen diaspora">Chechen diaspora</a> and their supporters promote 23 February as World Chechnya Day to commemorate the victims.
</p>
The Chechens and Ingush, along with the Karachai and Balkars, are represented in the <i>Confederation of Repressed Peoples</i>
(CRP), an organization that covers the former Soviet Union and aims to
support and rehabilitate the rights of the deported peoples.</div></div>
<h3><span class="mw-headline" id="Deportation_of_the_Crimean_Tatars">Deportation of the Crimean Tatars</span></h3><h3>Some activists, politicians, scholars, countries, and historians go even further and consider the deportation a crime of <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a> or <a href="https://en.wikipedia.org/wiki/Cultural_genocide" title="Cultural genocide">cultural genocide</a>. <a href="https://en.wikipedia.org/wiki/Norman_Naimark" title="Norman Naimark">Norman Naimark</a>
writes "[t]he Chechens and Ingush, the Crimean Tatars, and other
'punished peoples' of the wartime period were, indeed, slated for
elimination, if not physically, then as self-identifying nationalities."
Professor Lyman H. Legters argued that the Soviet penal system,
combined with its resettlement policies, should count as genocidal since
the sentences were borne most heavily specifically on certain ethnic
groups, and that a relocation of these ethnic groups, whose survival
depends on ties to its particular homeland, "had a genocidal effect
remediable only by restoration of the group to its homeland."
Political scientist Stephen Blank described it both as a deportation
and a genocide, a centuries-long Russian "technique of self-colonial
rule intended to eliminate" minorities. Soviet dissidents <a href="https://en.wikipedia.org/wiki/Ilya_Gabay" title="Ilya Gabay">Ilya Gabay</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pyotr_Grigorenko" title="Pyotr Grigorenko">Pyotr Grigorenko</a> both classified the event as a genocide. Historian <a href="https://en.wikipedia.org/wiki/Timothy_Snyder" title="Timothy Snyder">Timothy Snyder</a> included it in a list of Soviet policies that “meet the standard of genocide." Historians <a href="https://en.wikipedia.org/wiki/Alexandre_Bennigsen" title="Alexandre Bennigsen">Alexandre Bennigsen</a> and <a href="https://en.wikipedia.org/wiki/Marie_Bennigsen-Broxup" title="Marie Bennigsen-Broxup">Marie Bennigsen-Broxup</a>
included the case of Crimean Tatars and Meskhetian Turks as two
examples of successful genocides by Soviet governments. They summed it
up by saying that Crimean Tatars, "a nation which for over five
centuries had played a major part in the history of Eastern Europe has
simply ceased to exist". Polish scholar <a href="https://en.wikipedia.org/wiki/Tomasz_Kamusella" title="Tomasz Kamusella">Tomasz Kamusella</a>
observed that Moscow attempted an "unmaking of Crimean Tatars and their
languague" by not allowing them even to be registered as Crimean Tatars
since the deportation; they could only declare themselves as Tatars. It
wasn't until the 1989 census that Crimean Tatars were again recognized
as a separate nationality. The <a href="https://en.wikipedia.org/wiki/Crimean_Tatar_language" title="Crimean Tatar language">Crimean Tatar language</a> was only allowed to be taught again in Soviet schools since the 1980s.
</h3><div class="excerpt-block"><div class="excerpt"><p>On 12 December 2015, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ukrainian_Parliament" title="Ukrainian Parliament">Ukrainian Parliament</a>
issued a resolution recognizing this event as genocide and established
18 May as the "Day of Remembrance for the victims of the Crimean Tatar
genocide." The <a href="https://en.wikipedia.org/wiki/Saeima" title="Saeima">parliament of Latvia</a> recognized the event as an act of genocide on 9 May 2019. The <a href="https://en.wikipedia.org/wiki/Seimas" title="Seimas">Parliament of Lithuania</a> did the same on 6 June 2019.
Canadian Parliament passed a motion on June 10, 2019, recognizing the
Crimean Tatar deportation of 1944 (Sürgünlik) as a genocide perpetrated
by Soviet dictator Stalin, designating May 18 to be a day of
remembrance. On 26 April 1991 the Supreme Soviet of the Russian Socialist Federal Soviet Republic, under its chairman <a href="https://en.wikipedia.org/wiki/Boris_Yeltsin" title="Boris Yeltsin">Boris Yeltsin</a>,
passed the law On the Rehabilitation of Repressed Peoples with Article 2
denouncing all mass deportations as "Stalin's policy of defamation and <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>."
</p>
A minority dispute defining the event as genocide. According to Alexander Statiev, the <a href="https://en.wikipedia.org/wiki/Population_transfer_in_the_Soviet_Union" title="Population transfer in the Soviet Union">Soviet deportations</a> resulted in a "genocidal <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Death_rate" title="Death rate">death rate</a>", but Stalin did not have <a href="https://en.wikipedia.org/wiki/Genocidal_intent" title="Genocidal intent">the intent</a> to exterminate <a href="https://en.wikipedia.org/wiki/Population_transfer_in_the_Soviet_Union" title="Population transfer in the Soviet Union">these peoples</a>. He considers such deportations merely an example of <a href="https://en.wikipedia.org/wiki/Russification" title="Russification">Soviet assimilation</a> of "unwanted nations."<sup class="reference" id="cite_ref-FOOTNOTEStatiev2010243–264_180-0"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-FOOTNOTEStatiev2010243–264-180">[]</a></sup> According to <a href="https://en.wikipedia.org/wiki/Amir_Weiner" title="Amir Weiner">Amir Weiner</a>, the Soviet regime sought to eradicate "only" their "territorial identity". Such views were criticized by Jon Chang as "gentrified <a href="https://en.wikipedia.org/wiki/Racism" title="Racism">racism</a>" and <a href="https://en.wikipedia.org/wiki/Historical_revisionism" title="Historical revisionism">historical revisionism</a>. He noted that the deportations had been in fact based on ethnicity of victims.</div></div>
<h3><span class="mw-headline" id="Draining_of_the_Mesopotamian_Marshes">Draining of the Mesopotamian Marshes</span></h3><div class="excerpt-block"><div class="excerpt">
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Iraq_marshes_1994.jpg"><img class="mw-file-element" data-file-height="1296" data-file-width="1296" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Iraq_marshes_1994.jpg/220px-Iraq_marshes_1994.jpg" width="400" /></a><figcaption>A 1994 map of the Mesopotamian Marshes with the pink zones showing drained areas.</figcaption></figure>
<p>The <a href="https://en.wikipedia.org/wiki/Mesopotamian_Marshes" title="Mesopotamian Marshes">Mesopotamian Marshes</a> were drained in <a href="https://en.wikipedia.org/wiki/Iraq" title="Iraq">Iraq</a> and to a smaller degree in <a href="https://en.wikipedia.org/wiki/Iran" title="Iran">Iran</a> between the 1950s and 1990s to clear large areas of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Marshes" title="Marshes">marshes</a> in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Tigris-Euphrates_river_system" title="Tigris-Euphrates river system">Tigris-Euphrates river system</a>. The marshes formerly covered an area of around 20,000 km<sup>2</sup> (7,700 sq mi). The main sub-marshes, the <a href="https://en.wikipedia.org/wiki/Hawizeh_Marshes" title="Hawizeh Marshes">Hawizeh</a>, <a href="https://en.wikipedia.org/wiki/Central_Marshes" title="Central Marshes">Central</a>, and <a href="https://en.wikipedia.org/wiki/Hammar_Marshes" title="Hammar Marshes">Hammar</a> marshes, were drained at different times for different reasons.
</p><p>In the 1990s, the marshes were drained for political motives, namely to force the <a href="https://en.wikipedia.org/wiki/Marsh_Arabs" title="Marsh Arabs">Marsh Arabs</a> out of the area and to punish them for their role in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/1991_uprisings_in_Iraq" title="1991 uprisings in Iraq">1991 uprising</a> against Saddam Hussein's government. However, the government's stated reasoning was to reclaim land for agriculture and exterminate breeding grounds for mosquitoes.
The displacement of more than 200,000 of the Ahwaris, and the
associated state-sponsored campaign of violence against them, has led
the United States and others to describe the draining of the marshes as <a href="https://en.wikipedia.org/wiki/Ecocide" title="Ecocide">ecocide</a> or <a href="https://en.wikipedia.org/wiki/Ethnic_cleansing" title="Ethnic cleansing">ethnic cleansing</a>.
</p>
The draining of the Mesopotamian Marshes has been described by the <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a> as a "tragic human and environmental catastrophe" on par with the <a href="https://en.wikipedia.org/wiki/Deforestation_of_the_Amazon_rainforest" title="Deforestation of the Amazon rainforest">deforestation of the Amazon rainforest</a> and by other observers as one of the worst environmental disasters of the 20th century.</div></div>
<h3><span class="mw-headline" id="Genocide_of_Yazidis_by_ISIL">Genocide of Yazidis by ISIL</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"><br /></div><div class="excerpt">
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Yezidi_victims_Monument_(Yerevan)_(3).jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img class="mw-file-element" data-file-height="3397" data-file-width="3011" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3f/Yezidi_victims_Monument_%28Yerevan%29_%283%29.jpg/220px-Yezidi_victims_Monument_%28Yerevan%29_%283%29.jpg" width="355" /></a><figcaption>Yazidi Genocide Monument in <a href="https://en.wikipedia.org/wiki/Yerevan" title="Yerevan">Yerevan</a>, <a href="https://en.wikipedia.org/wiki/Armenia" title="Armenia">Armenia</a></figcaption></figure>
<p>Many international organisations, governments and parliaments, as
well as groups have classified ISIL's treatment of the Yazidis as
genocide, and condemned it as such. The Genocide of Yazidis has been
officially recognized by several bodies of the <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a> and the <a href="https://en.wikipedia.org/wiki/European_Parliament" title="European Parliament">European Parliament</a>. Some states have recognized it as well, including the <a href="https://en.wikipedia.org/wiki/National_Assembly_(Armenia)" title="National Assembly (Armenia)">National Assembly of Armenia</a>, the <a href="https://en.wikipedia.org/wiki/Parliament_of_Australia" title="Parliament of Australia">Australian parliament</a>, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_the_United_Kingdom" title="House of Commons of the United Kingdom">British Parliament</a>, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_Canada" title="House of Commons of Canada">Canadian parliament</a>, and the <a href="https://en.wikipedia.org/wiki/United_States_House_of_Representatives" title="United States House of Representatives">United States House of Representatives</a>. Multiple individual human rights activists such as <a href="https://en.wikipedia.org/wiki/Nazand_Begikhani" title="Nazand Begikhani">Nazand Begikhani</a> and Dr. <a href="https://en.wikipedia.org/wiki/Widad_Akrawi" title="Widad Akrawi">Widad Akrawi</a> have also advocated for this view.
</p><p>In 2017, CNN journalists Jomana Karadsheh and Chris Jackson
interviewed former Yazidi captives and exclusively filmed the Daesh
Criminal Investigations Unit (DCIU), a team of Iraqi Kurdish and western
investigators who have been operating secretly in Northern Iraq, for
more than two years, collecting evidence of ISIS’ war crimes.
</p>
<ul><li><a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a>:
<ul><li>In a March 2015 report, the persecution of the Yazidi people was qualified as a genocide by the <a href="https://en.wikipedia.org/wiki/Office_of_the_United_Nations_High_Commissioner_for_Human_Rights" title="Office of the United Nations High Commissioner for Human Rights">Office of the United Nations High Commissioner for Human Rights</a> (UNHCR). The organization cited the numerous atrocities such as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Forced_religious_conversion" title="Forced religious conversion">forced religious conversion</a> and <a href="https://en.wikipedia.org/wiki/Sexual_slavery" title="Sexual slavery">sexual slavery</a> as being parts of an overall malicious campaign.</li><li>In August 2017, the <a href="https://en.wikipedia.org/wiki/Independent_International_Commission_of_Inquiry_on_the_Syrian_Arab_Republic" title="Independent International Commission of Inquiry on the Syrian Arab Republic">Independent International Commission of Inquiry on the Syrian Arab Republic</a> of the <a href="https://en.wikipedia.org/wiki/United_Nations_Human_Rights_Council" title="United Nations Human Rights Council">United Nations Human Rights Council</a>
(UNHRC) stated that 'ISIL committed the crime of genocide by seeking to
destroy the Yazidis through killings, sexual slavery, enslavement,
torture, forcible displacement, the transfer of children and measures
intended to prohibit the birth of Yazidi children.' It added that the
genocide was ongoing, and stating that the international community still
must recognize the detrimental effects of the genocide. The Commission
wrote that, while some countries may choose to overlook the idea of the
genocide, the atrocities need to be understood and the international
community needs to bring the killings to an end.</li><li>In 2018, the Security Council team enforced the idea of a new
accountability team that would collect evidence of the international
crimes committed by the Islamic State. However, the international
community has not been in full support of this idea, because it can
sometimes oversee the crimes that other armed groups are involved in.</li><li>On 10 May 2021, the United Nations Investigative Team to Promote
Accountability for Crimes Committed by Da'esh/ISIL (UNITAD) determined
that ISIL's actions in Iraq constituted genocide.</li></ul></li><li><a href="https://en.wikipedia.org/wiki/Council_of_Europe" title="Council of Europe">Council of Europe</a>: On 27 January 2016, the <a href="https://en.wikipedia.org/wiki/Parliamentary_Assembly_of_the_Council_of_Europe" title="Parliamentary Assembly of the Council of Europe">Parliamentary Assembly of the Council of Europe</a>
adopted a resolution stating: "individuals who act in the name of the
terrorist entity which calls itself 'Islamic State' (Daesh) ... have
perpetrated acts of genocide and other serious crimes punishable under
international law. States should act on the presumption that Daesh
commits genocide and should be aware that this entails action under the
1948 United Nations Convention on the Prevention and Punishment of the
Crime of Genocide." However, it did not identify victims.</li><li><a href="https://en.wikipedia.org/wiki/European_Union" title="European Union">European Union</a>: On 4 February 2016, the <a href="https://en.wikipedia.org/wiki/European_Parliament" title="European Parliament">European Parliament</a>
unanimously passed a resolution to recognise 'that the so-called
'ISIS/Daesh' is committing genocide against Christians and Yazidis, and
other religious and ethnic minorities, who do not agree with the
so-called 'ISIS/Daesh' interpretation of Islam, and that this therefore
entails action under the 1948 United Nations Convention on the
Prevention and Punishment of the Crime of Genocide.' Additionally, it called for those who intentionally committed
atrocities for ethnic or religious reasons to be brought to justice for
violating international law, and committing crimes against humanity, and
genocide.</li><li><a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a>: The <a href="https://en.wikipedia.org/wiki/United_States_Department_of_State" title="United States Department of State">United States Department of State</a> has formally recognised the Yazidi genocide in areas under the control of ISIS in 2016 and 2017. On 14 March 2016, the <a href="https://en.wikipedia.org/wiki/United_States_House_of_Representatives" title="United States House of Representatives">United States House of Representatives</a> voted unanimously 393-0 that violent actions performed against Yazidis, Christians, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Shia" title="Shia">Shia</a> and other groups by ISIL were acts of genocide. Days later on 17 March 2016, <a href="https://en.wikipedia.org/wiki/United_States_Secretary_of_State" title="United States Secretary of State">United States Secretary of State</a> <a href="https://en.wikipedia.org/wiki/John_Kerry" title="John Kerry">John Kerry</a> declared that the violence initiated by ISIL against the Yazidis and others amounted to genocide.</li><li><a href="https://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a>: On 20 April 2016, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_the_United_Kingdom" title="House of Commons of the United Kingdom">House of Commons of the United Kingdom</a>
unanimously supported a motion to declare that the treatment of Yazidis
and Christians by the Islamic State amounted to genocide, to condemn it
as such, and to refer the issue to the UN Security Council. In doing
so, <a href="https://en.wikipedia.org/wiki/Conservative_Party_(UK)" title="Conservative Party (UK)">Conservative</a>
MPs defied their own party's government, who had tried to dissuade them
from making such a statement, because of the Foreign Office legal
department's long-standing policy (dating back to the 1948 passing of
the Genocide Convention) of refusing to give a legal description to
potential war crimes. Foreign Office secretary <a href="https://en.wikipedia.org/wiki/Tobias_Ellwood" title="Tobias Ellwood">Tobias Ellwood</a>
– who was jeered at and interrupted by MPs during his speech in the
debate – stated that he personally believed genocide had taken place,
but that it was not up to politicians to make that determination, but to
the courts. Furthermore, on 23 March 2017, the regional devolved <a href="https://en.wikipedia.org/wiki/Scottish_Parliament" title="Scottish Parliament">Scottish Parliament</a>
adopted a motion stating: '[The Scottish Parliament] recognises and
condemns the genocide perpetrated against the Yezidi people by Daesh
[ISIS]; acknowledges the great human suffering and loss that have been
inflicted by bigotry, brutality and religious intolerance, [and] further
acknowledges and condemns the crimes perpetrated by Daesh against
Muslims, Christians, Arabs, Kurds and all of the religious and ethnic
communities of Iraq and Syria; welcomes the actions of the US Congress,
the European Parliament, the French Senate, the UN and others in
formally recognising the genocide'.</li><li><a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a>: On 25 October 2016, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_Canada" title="House of Commons of Canada">House of Commons of Canada</a> unanimously supported a motion tabled by MP <a href="https://en.wikipedia.org/wiki/Michelle_Rempel_Garner" title="Michelle Rempel Garner">Michelle Rempel Garner</a> (<a href="https://en.wikipedia.org/wiki/Conservative_Party_of_Canada" title="Conservative Party of Canada">CPC</a>)
to recognise that ISIS was committing genocide against the Yazidi
people, to acknowledge that ISIS still kept many Yazidi women and girls
captive as sex slaves, to support and take action on a recent UN
commission report, and provide asylum to Yazidi women and girls within
120 days.</li><li><a href="https://en.wikipedia.org/wiki/France" title="France">France</a>: On 6 December 2016, the <a href="https://en.wikipedia.org/wiki/Senate_(France)" title="Senate (France)">French Senate</a>
unanimously approved a resolution stating that acts committed by the
Islamic State against "the Christian and Yazidi populations, other
minorities and civilians" were "war crimes", "crimes against humanity",
and constituted a "genocide". It also invited the government to "use all
legal channels" to have these crimes recognised, and the perpetrators
tried. The <a href="https://en.wikipedia.org/wiki/National_Assembly_(France)" title="National Assembly (France)">National Assembly</a> adopted a similar resolution two days later (originally tabled on 25 May 2016 by <a href="https://en.wikipedia.org/wiki/Yves_Fromion" title="Yves Fromion">Yves Fromion</a> of <a href="https://en.wikipedia.org/wiki/The_Republicans_(France)" title="The Republicans (France)">The Republicans</a>), with the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Socialist_group,_associated_(National_Assembly)" title="Socialist group, associated (National Assembly)">Socialist, Ecologist and Republican group</a> abstaining and the other groups approving.</li><li><a href="https://en.wikipedia.org/wiki/Armenia" title="Armenia">Armenia</a>:
In January 2018, the Armenian parliament recognised and condemned the
2014 genocide of Yazidis by the Islamic State, and called on the
international community to conduct an international investigation into
the events.</li><li><a href="https://en.wikipedia.org/wiki/Israel" title="Israel">Israel</a>: On 21 November 2018, a bill tabled by opposition MP <a href="https://en.wikipedia.org/wiki/Ksenia_Svetlova" title="Ksenia Svetlova">Ksenia Svetlova</a> (<a href="https://en.wikipedia.org/wiki/Zionist_Union" title="Zionist Union">ZU</a>) to recognise the Islamic State's killing of Yazidis as a genocide was defeated in a 58 to 38 vote in the <a href="https://en.wikipedia.org/wiki/Knesset" title="Knesset">Knesset</a>. The <a href="https://en.wikipedia.org/wiki/Thirty-fourth_government_of_Israel" title="Thirty-fourth government of Israel">coalition parties</a> motivated their rejection of the bill by saying that the United Nations had not yet recognised it as a genocide.</li><li><a href="https://en.wikipedia.org/wiki/Iraq" title="Iraq">Iraq</a>: On 1 March 2021, <a href="https://en.wikipedia.org/wiki/Council_of_Representatives_of_Iraq" title="Council of Representatives of Iraq">the Iraq parliament</a> passed the Yazidi [Female] Survivors Bill which provides assistance to survivors and "determines the atrocities perpetrated by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Daesh" title="Daesh">Daesh</a> against the Yazidis, Turkmen, Christians and Shabaks to be genocide and crimes against humanity."
The law provides compensation, measures for rehabilitation and
reintegration, pensions, provision of land, housing, and education, and a
quota in public sector employment.
On 10 May 2021, the United Nations Investigative Team to Promote
Accountability for Crimes Committed by Da'esh/ISIL (UNITAD) determined
that ISIL's actions in Iraq constituted genocide.</li><li><a href="https://en.wikipedia.org/wiki/Belgium" title="Belgium">Belgium</a>: On 30 June 2021, the Foreign Relations Commission of the <a href="https://en.wikipedia.org/wiki/Chamber_of_Representatives_(Belgium)" title="Chamber of Representatives (Belgium)">Belgian Chamber of Representatives</a> unanimously approved a resolution by opposition representatives <a href="https://en.wikipedia.org/wiki/Georges_Dallemagne" title="Georges Dallemagne">Georges Dallemagne</a> (<a href="https://en.wikipedia.org/wiki/Humanist_Democratic_Centre" title="Humanist Democratic Centre">cdH</a>) and <a href="https://en.wikipedia.org/wiki/Koen_Metsu" title="Koen Metsu">Koen Metsu</a> (<a href="https://en.wikipedia.org/wiki/New_Flemish_Alliance" title="New Flemish Alliance">N-VA</a>)
to recognise ISIL's August 2014 massacre of thousands of Yazidi men and
enslavement of thousands of Yazidi women and children as genocide. The
resolution, which would likely also pass with overwhelming approval in
the Chamber itself, called on the Belgian government to increase its
efforts to support victims, and prosecute perpetrators (either at the <a href="https://en.wikipedia.org/wiki/International_Criminal_Court" title="International Criminal Court">International Criminal Court</a>, or at a new ad hoc tribunal).
On 17 July 2021, the Belgian parliament unanimously voted to recognize
the suffering of the Yazidis at the hands of the Islamic State (ISIS) in
2014 as a genocide.</li><li><a href="https://en.wikipedia.org/wiki/Netherlands" title="Netherlands">Netherlands</a>: On 6 July 2021, the <a href="https://en.wikipedia.org/wiki/House_of_Representatives_(Netherlands)" title="House of Representatives (Netherlands)">Dutch House of Representatives</a> unanimously passed a motion tabled by MP <a href="https://en.wikipedia.org/wiki/Anne_Kuik" title="Anne Kuik">Anne Kuik</a> (<a href="https://en.wikipedia.org/wiki/Christian_Democratic_Appeal" title="Christian Democratic Appeal">CDA</a>) which recognised the crimes of Islamic State against the Yazidi population as a genocide and crimes against humanity.</li><li><a href="https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a>: On 19 January 2023, the German <a href="https://en.wikipedia.org/wiki/Bundestag" title="Bundestag">Bundestag</a> unanimously recognized the crimes against Yazidis as genocide.
The resolution, which was jointly tabled by the government and the
opposition, also calls for prosecution of the perpetrators and aid for
rebuilding Yazidi villages.</li></ul></div></div>
<h3><span class="mw-headline" id="Greek_genocide">Greek genocide</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note">This section is an excerpt from <a href="https://en.wikipedia.org/wiki/Greek_genocide#Political_recognition" title="Greek genocide">Greek genocide § Political recognition</a>.<span class="mw-editsection-like plainlinks"><span class="mw-editsection-bracket">[</span><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Greek_genocide&action=edit#Political_recognition">edit</a><span class="mw-editsection-bracket">]</span></span></div><div class="excerpt">
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Pontic_genocide_memorial,_Argos.jpg"><img class="mw-file-element" data-file-height="2250" data-file-width="4000" height="225" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/Pontic_genocide_memorial%2C_Argos.jpg/220px-Pontic_genocide_memorial%2C_Argos.jpg" width="400" /></a><figcaption>Monument in <a href="https://en.wikipedia.org/wiki/Argos,_Peloponnese" title="Argos, Peloponnese">Argos</a>, Greece for the Greek genocide and the Holocaust.</figcaption></figure>
<p>Following an initiative of MPs of the so-called "patriotic" wing of the ruling <a href="https://en.wikipedia.org/wiki/PASOK" title="PASOK">PASOK</a> party's parliamentary group and like-minded MPs of conservative <a href="https://en.wikipedia.org/wiki/New_Democracy_(Greece)" title="New Democracy (Greece)">New Democracy</a>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Greek_Parliament" title="Greek Parliament">Greek Parliament</a>
passed two laws on the fate of the Ottoman Greeks; the first in 1994
and the second in 1998. The decrees were published in the Greek <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Efimerida_tis_Kyberniseos" title="Efimerida tis Kyberniseos"><i>Government Gazette</i></a> on 8 March 1994 and 13 October 1998 respectively. The 1994 decree, created by <a href="https://en.wikipedia.org/wiki/Georgios_Daskalakis" title="Georgios Daskalakis">Georgios Daskalakis</a>, affirmed the genocide in the Pontus region of Asia Minor and designated 19 May (the <a href="https://en.wikipedia.org/wiki/Commemoration_of_Atat%C3%BCrk,_Youth_and_Sports_Day" title="Commemoration of Atatürk, Youth and Sports Day">day</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mustafa_Kemal" title="Mustafa Kemal">Mustafa Kemal</a> landed in <a href="https://en.wikipedia.org/wiki/Samsun" title="Samsun">Samsun</a> in 1919) a day of commemoration (called Pontian Greek Genocide Remembrance Day)
while the 1998 decree affirmed the genocide of Greeks in Asia Minor as a
whole and designated 14 September a day of commemoration.
These laws were signed by the President of Greece but were not
immediately ratified after political interventions. After leftist
newspaper <a href="https://en.wikipedia.org/wiki/I_Avgi" title="I Avgi">I Avgi</a>
initiated a campaign against the application of this law, the subject
became subject of a political debate. The president of the
left-ecologist <a href="https://en.wikipedia.org/wiki/Synaspismos" title="Synaspismos">Synaspismos</a> party <a href="https://en.wikipedia.org/wiki/Nikos_Konstantopoulos" title="Nikos Konstantopoulos">Nikos Konstantopoulos</a> and historian Angelos Elefantis,
known for his books on the history of Greek communism, were two of the
major figures of the political left who expressed their opposition to
the decree. However, the non-parliamentary <a href="https://en.wikipedia.org/wiki/Left-wing_nationalism" title="Left-wing nationalism">left-wing nationalist</a>
intellectual and author George Karabelias bitterly criticized Elefantis
and others opposing the recognition of genocide and called them
"revisionist historians", accusing the Greek mainstream left of a
"distorted ideological evolution". He said that for the Greek left 19
May is a "day of amnesia".
</p><p>In the late 2000s the <a href="https://en.wikipedia.org/wiki/Communist_Party_of_Greece" title="Communist Party of Greece">Communist Party of Greece</a> adopted the term "Genocide of the Pontic (Greeks)" (<span title="Greek-language text"><span lang="el">Γενοκτονία Ποντίων</span></span>) in its official newspaper <i><a href="https://en.wikipedia.org/wiki/Rizospastis" title="Rizospastis">Rizospastis</a></i> and participates in memorial events.
</p><p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Republic_of_Cyprus" title="Republic of Cyprus">Republic of Cyprus</a> has also officially called the events "Greek Genocide in Pontus of Asia Minor".
</p><p>In response to the 1998 law, the Turkish government released a
statement which claimed that describing the events as genocide was
"without any historical basis". "We condemn and protest this resolution"
a Turkish Foreign Ministry statement said. "With this resolution the
Greek Parliament, which in fact has to apologize to the Turkish people
for the large-scale destruction and massacres Greece perpetrated in <a href="https://en.wikipedia.org/wiki/Anatolia" title="Anatolia">Anatolia</a>,
not only sustains the traditional Greek policy of distorting history,
but it also displays that the expansionist Greek mentality is still
alive," the statement added.
</p><p>On 11 March 2010, <a href="https://en.wikipedia.org/wiki/Sweden" title="Sweden">Sweden</a>'s <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Parliament_of_Sweden" title="Parliament of Sweden">Riksdag</a>
passed a motion recognising "as an act of genocide the killing of
Armenians, Assyrians/Syriacs/Chaldeans and Pontic Greeks in 1915".
</p><p>On 14 May 2013, the government of <a href="https://en.wikipedia.org/wiki/New_South_Wales" title="New South Wales">New South Wales</a> was submitted a genocide recognition motion by <a href="https://en.wikipedia.org/wiki/Fred_Nile" title="Fred Nile">Fred Nile</a> of the <a href="https://en.wikipedia.org/wiki/Christian_Democratic_Party_(Australia)" title="Christian Democratic Party (Australia)">Christian Democratic Party</a>, which was later passed making it the fourth political entity to recognise the genocide.
</p><p>In March 2015, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/National_Assembly_of_Armenia" title="National Assembly of Armenia">National Assembly of Armenia</a> unanimously adopted a resolution recognizing both the Greek and Assyrian genocides.
</p>
In April 2015, the <a href="https://en.wikipedia.org/wiki/States_General_of_the_Netherlands" title="States General of the Netherlands">States General of the Netherlands</a> and the <a href="https://en.wikipedia.org/wiki/Austrian_Parliament" title="Austrian Parliament">Austrian Parliament</a> passed resolutions recognizing the Greek and Assyrian genocides.</div></div>
<h3><span id="1888.E2.80.931893_Uprisings_of_Hazaras"></span><span class="mw-headline" id="1888–1893_Uprisings_of_Hazaras">1888–1893 Uprisings of Hazaras</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"></div><div class="excerpt">
The Hazara diaspora mourns the deaths of the victims of the Hazara
uprisings of the 1890s on September 25 (called the "Hazara Black Day")
and it wants the International community to recognize the subjugation of
the Hazaras as a <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a>.</div></div>
<h3><span class="mw-headline" id="Holocaust">Holocaust</span></h3><div class="hatnote navigation-not-searchable" role="note">Further information: <a href="https://en.wikipedia.org/wiki/International_response_to_the_Holocaust" title="International response to the Holocaust">International response to the Holocaust</a>, <a href="https://en.wikipedia.org/wiki/Holocaust_denial" title="Holocaust denial">Holocaust denial</a>, and <a href="https://en.wikipedia.org/wiki/Legality_of_Holocaust_denial" title="Legality of Holocaust denial">Legality of Holocaust denial</a></div>
<p>There is a virtually unanimous consensus in the international community that <a href="https://en.wikipedia.org/wiki/The_Holocaust" title="The Holocaust">the Holocaust</a> was committed primarily by <a href="https://en.wikipedia.org/wiki/Nazi_Germany" title="Nazi Germany">Nazi Germany</a> against the <a href="https://en.wikipedia.org/wiki/Jews" title="Jews">Jews</a> and other minorities in the early 1940s, due to <a href="https://en.wikipedia.org/wiki/Evidence_and_documentation_for_the_Holocaust" title="Evidence and documentation for the Holocaust">overwhelming evidence</a>, although there are some differences in <a href="https://en.wikipedia.org/wiki/Names_of_the_Holocaust" title="Names of the Holocaust">names and definitions</a>, periodisation, scope (for example, whether the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Romani_genocide" title="Romani genocide">1941–44 Romani genocide/Porajmos</a> should be recognised as part of the Holocaust, or as a separate genocide committed simultaneously with the Holocaust), <a href="https://en.wikipedia.org/wiki/Responsibility_for_the_Holocaust" title="Responsibility for the Holocaust">attributed responsibility</a>, and <a href="https://en.wikipedia.org/wiki/Functionalism%E2%80%93intentionalism_debate" title="Functionalism–intentionalism debate">motivation</a>. There is a wide range of <a href="https://en.wikipedia.org/wiki/Holocaust_memorial_days" title="Holocaust memorial days">Holocaust memorial days</a>, <a href="https://en.wikipedia.org/wiki/List_of_Holocaust_memorials_and_museums" title="List of Holocaust memorials and museums">memorials and museums</a>, and <a href="https://en.wikipedia.org/wiki/Holocaust_education" title="Holocaust education">education policies</a>.
Unlike with other genocides, much of the politics surrounding the
Holocaust are not about formally recognising it in political statements
(since there is already a strong consensus), but focus on its
importance, which aspects should be emphasised, how to prevent it or
similar genocides from happening again, how to combat <a href="https://en.wikipedia.org/wiki/Holocaust_denial" title="Holocaust denial">Holocaust denial</a>, and <a href="https://en.wikipedia.org/wiki/Legality_of_Holocaust_denial" title="Legality of Holocaust denial">whether it should be illegal to deny it</a>. Some regimes, politicians or organisations may occasionally deny or <a href="https://en.wikipedia.org/wiki/Holocaust_trivialization" title="Holocaust trivialization">downplay</a> the Holocaust for various reasons, such as <a href="https://en.wikipedia.org/wiki/Antisemitism" title="Antisemitism">antisemitism</a>, in opposition to the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/State_of_Israel" title="State of Israel">State of Israel</a>, or for comparisons with other genocides deemed more or similarly important.
</p>
<h3><span class="mw-headline" id="Holodomor">Holodomor</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note">This section is an excerpt from <a href="https://en.wikipedia.org/wiki/Holodomor_in_modern_politics#Recognition" title="Holodomor in modern politics">Holodomor in modern politics § Recognition</a>.<span class="mw-editsection-like plainlinks"><span class="mw-editsection-bracket">[</span><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Holodomor_in_modern_politics&action=edit">edit</a><span class="mw-editsection-bracket">]</span></span></div><div class="excerpt">
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Holodomor_recognition_by_country_2.png"><img class="mw-file-element" data-file-height="3427" data-file-width="7192" height="191" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Holodomor_recognition_by_country_2.png/300px-Holodomor_recognition_by_country_2.png" width="400" /></a><figcaption>Recognition of the Holodomor by country</figcaption></figure>
<p>Since 2006, the Holodomor has been recognised as a <a href="https://en.wikipedia.org/wiki/Genocide" title="Genocide">genocide</a> by the <a href="https://en.wikipedia.org/wiki/Verkhovna_Rada" title="Verkhovna Rada">Ukrainian parliament</a>. Ukraine's <a href="https://en.wikipedia.org/wiki/Ministry_of_Foreign_Affairs_(Ukraine)" title="Ministry of Foreign Affairs (Ukraine)">Ministry of Foreign Affairs</a> has run campaigns and lobbied the <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a> and the <a href="https://en.wikipedia.org/wiki/Council_of_Europe" title="Council of Europe">Council of Europe</a> to recognise the Holodomor as a genocide internationally. Sovereign states to have recognized Holodomor as genocide<sup> </sup>include <a href="https://en.wikipedia.org/wiki/Australia" title="Australia">Australia</a>, <a href="https://en.wikipedia.org/wiki/Belgium" title="Belgium">Belgium</a>, <a href="https://en.wikipedia.org/wiki/Brazil" title="Brazil">Brazil</a>, <a href="https://en.wikipedia.org/wiki/Bulgaria" title="Bulgaria">Bulgaria</a>, <a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a>, <a href="https://en.wikipedia.org/wiki/Colombia" title="Colombia">Colombia</a>, <a href="https://en.wikipedia.org/wiki/Czech_Republic" title="Czech Republic">Czech Republic</a>, <a href="https://en.wikipedia.org/wiki/Ecuador" title="Ecuador">Ecuador</a>, <a href="https://en.wikipedia.org/wiki/Estonia" title="Estonia">Estonia</a>, <a href="https://en.wikipedia.org/wiki/France" title="France">France</a>, <a href="https://en.wikipedia.org/wiki/Georgia_(country)" title="Georgia (country)">Georgia</a>, <a href="https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a>, <a href="https://en.wikipedia.org/wiki/Hungary" title="Hungary">Hungary</a>, <a href="https://en.wikipedia.org/wiki/Iceland" title="Iceland">Iceland</a>, <a href="https://en.wikipedia.org/wiki/Ireland" title="Ireland">Ireland</a>'s senate, <a href="https://en.wikipedia.org/wiki/Italy" title="Italy">Italy</a>, <a href="https://en.wikipedia.org/wiki/Latvia" title="Latvia">Latvia</a>, <a href="https://en.wikipedia.org/wiki/Lithuania" title="Lithuania">Lithuania</a>, <a href="https://en.wikipedia.org/wiki/Mexico" title="Mexico">Mexico</a>, <a href="https://en.wikipedia.org/wiki/Moldova" title="Moldova">Moldova</a>, <a href="https://en.wikipedia.org/wiki/Netherlands" title="Netherlands">Netherlands</a>, <a href="https://en.wikipedia.org/wiki/Paraguay" title="Paraguay">Paraguay</a>, <a href="https://en.wikipedia.org/wiki/Peru" title="Peru">Peru</a>, <a href="https://en.wikipedia.org/wiki/Poland" title="Poland">Poland</a>, <a href="https://en.wikipedia.org/wiki/Portugal" title="Portugal">Portugal</a>, <a href="https://en.wikipedia.org/wiki/Romania" title="Romania">Romania</a>, <a href="https://en.wikipedia.org/wiki/Slovenia" title="Slovenia">Slovenia</a>, <a href="https://en.wikipedia.org/wiki/Ukraine" title="Ukraine">Ukraine</a>, <a href="https://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a>, <a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a>, the <a href="https://en.wikipedia.org/wiki/Holy_See" title="Holy See">Holy See</a> in <a href="https://en.wikipedia.org/wiki/Vatican_City" title="Vatican City">Vatican City</a> and <a href="https://en.wikipedia.org/wiki/Wales" title="Wales">Wales</a>.<sup> </sup>As the <a href="https://en.wikipedia.org/wiki/United_States_Congress" title="United States Congress">United States Congress</a> passed resolution of recognition through the <a href="https://en.wikipedia.org/wiki/United_States_Senate" title="United States Senate">United States Senate</a> and the <a href="https://en.wikipedia.org/wiki/United_States_House_of_Representatives" title="United States House of Representatives">United States House of Representatives</a>. Similarly, governments and parliaments of several other countries have
also officially recognized the Holodomor as an act of genocide.
</p><p>In November 2022, the Holodomor was recognized as a genocide by <a href="https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a>, <a href="https://en.wikipedia.org/wiki/Ireland" title="Ireland">Ireland</a>'s senate, <a href="https://en.wikipedia.org/wiki/Moldova" title="Moldova">Moldova</a>, <a href="https://en.wikipedia.org/wiki/Romania" title="Romania">Romania</a> and the <a href="https://en.wikipedia.org/wiki/Belarusian_opposition" title="Belarusian opposition">Belarusian opposition in exile</a>. <a href="https://en.wikipedia.org/wiki/Pope_Francis" title="Pope Francis">Pope Francis</a> compared the Russian war in Ukraine with its targeted <a class="mw-redirect" href="https://en.wikipedia.org/wiki/October%E2%80%93November_2022_nationwide_missile_strikes_on_Ukraine" title="October–November 2022 nationwide missile strikes on Ukraine">destruction of civilian infrastructure</a> to the "terrible Holodomor Genocide", during an address at St. Peter's Square. As of March 2024, 35 countries recognise the Holodomor as a genocide.
</p><p>The following countries have recognised the Holodomor as a genocide:
</p>
<div class="div-col" style="column-width: 20em;">
<ul><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="640" data-file-width="1280" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/88/Flag_of_Australia_%28converted%29.svg/23px-Flag_of_Australia_%28converted%29.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Australia" title="Australia">Australia</a>, 28 October 1993</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/41/Flag_of_Austria.svg/23px-Flag_of_Austria.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Austria" title="Austria">Austria</a>, 16 December 2022<span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Flag_of_Belgium_%28civil%29.svg/23px-Flag_of_Belgium_%28civil%29.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Belgium" title="Belgium">Belgium</a>, 10 March 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="504" data-file-width="720" height="15" src="https://upload.wikimedia.org/wikipedia/en/thumb/0/05/Flag_of_Brazil.svg/22px-Flag_of_Brazil.svg.png" width="22" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Brazil" title="Brazil">Brazil</a>, 26 April 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1000" height="14" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Flag_of_Bulgaria.svg/23px-Flag_of_Bulgaria.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Bulgaria" title="Bulgaria">Bulgaria</a>, 1 February 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Flag_of_Canada_%28Pantone%29.svg/23px-Flag_of_Canada_%28Pantone%29.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Canada" title="Canada">Canada</a>, 20 June 2003</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/21/Flag_of_Colombia.svg/23px-Flag_of_Colombia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Colombia" title="Colombia">Colombia</a>, 21 December 2007</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Flag_of_Croatia.svg/23px-Flag_of_Croatia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Croatia" title="Croatia">Croatia</a>, moved 15 June 2023, approved 28 June 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Flag_of_the_Czech_Republic.svg/23px-Flag_of_the_Czech_Republic.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Czech_Republic" title="Czech Republic">Czech Republic</a>, 6 April 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="960" data-file-width="1440" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e8/Flag_of_Ecuador.svg/23px-Flag_of_Ecuador.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Ecuador" title="Ecuador">Ecuador</a>, 30 October 2007</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="630" data-file-width="990" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Flag_of_Estonia.svg/23px-Flag_of_Estonia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Estonia" title="Estonia">Estonia</a>, 20 October 1993</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/en/thumb/c/c3/Flag_of_France.svg/23px-Flag_of_France.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/France" title="France">France</a>, 28 March 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Flag_of_Georgia.svg/23px-Flag_of_Georgia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Georgia_(country)" title="Georgia (country)">Georgia</a>, 20 December 2005</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1000" height="14" src="https://upload.wikimedia.org/wikipedia/en/thumb/b/ba/Flag_of_Germany.svg/23px-Flag_of_Germany.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a>, 30 November 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Flag_of_Hungary.svg/23px-Flag_of_Hungary.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Hungary" title="Hungary">Hungary</a>, 26 November 2003</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="900" data-file-width="1250" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/ce/Flag_of_Iceland.svg/21px-Flag_of_Iceland.svg.png" width="21" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Iceland" title="Iceland">Iceland</a>, 22 March 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Flag_of_Ireland.svg/23px-Flag_of_Ireland.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Republic_of_Ireland" title="Republic of Ireland">Ireland</a>, 24 November 2022 (resolution passed by the <a href="https://en.wikipedia.org/wiki/Seanad_%C3%89ireann" title="Seanad Éireann">Seanad</a>, still needed from the <a href="https://en.wikipedia.org/wiki/D%C3%A1il_%C3%89ireann" title="Dáil Éireann">Dáil</a>)</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="1000" data-file-width="1500" height="15" src="https://upload.wikimedia.org/wikipedia/en/thumb/0/03/Flag_of_Italy.svg/23px-Flag_of_Italy.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Italy" title="Italy">Italy</a>, 26 July 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/84/Flag_of_Latvia.svg/23px-Flag_of_Latvia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Latvia" title="Latvia">Latvia</a>, 13 March 2008<sup class="reference" id="cite_ref-Holodomor_in_modern_politics_Holodomor_Education_251-8"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-Holodomor_in_modern_politics_Holodomor_Education-251">[250]</a></sup></li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1000" height="14" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Flag_of_Lithuania.svg/23px-Flag_of_Lithuania.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Lithuania" title="Lithuania">Lithuania</a>, 24 November 2005</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="307" data-file-width="512" height="14" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Flag_of_Luxembourg.svg/23px-Flag_of_Luxembourg.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Luxembourg" title="Luxembourg">Luxembourg</a>, 13 June 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="560" data-file-width="980" height="13" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Flag_of_Mexico.svg/23px-Flag_of_Mexico.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Mexico" title="Mexico">Mexico</a>, 19 February 2008</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="900" data-file-width="1800" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/27/Flag_of_Moldova.svg/23px-Flag_of_Moldova.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Moldova" title="Moldova">Moldova</a>, 24 November 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Flag_of_the_Netherlands.svg/23px-Flag_of_the_Netherlands.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Netherlands" title="Netherlands">Netherlands</a>, 7 July 2023<sup class="reference" id="cite_ref-285">[</sup>r 2007</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Flag_of_Peru.svg/23px-Flag_of_Peru.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Peru" title="Peru">Peru</a>, 19 June 2007</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="800" data-file-width="1280" height="14" src="https://upload.wikimedia.org/wikipedia/en/thumb/1/12/Flag_of_Poland.svg/23px-Flag_of_Poland.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Poland" title="Poland">Poland</a>, 4 December 2006</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="400" data-file-width="600" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Flag_of_Portugal.svg/23px-Flag_of_Portugal.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Portugal" title="Portugal">Portugal</a>, 2 March 2017</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="400" data-file-width="600" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Flag_of_Romania.svg/23px-Flag_of_Romania.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Romania" title="Romania">Romania</a>, 24 November 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="900" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Flag_of_Slovakia.svg/23px-Flag_of_Slovakia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Slovakia" title="Slovakia">Slovakia</a>, 20 June 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Flag_of_Slovenia.svg/23px-Flag_of_Slovenia.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Slovenia" title="Slovenia">Slovenia</a>, 23 May 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="800" data-file-width="1200" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/49/Flag_of_Ukraine.svg/23px-Flag_of_Ukraine.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Ukraine" title="Ukraine">Ukraine</a>, 28 November 2006</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="600" data-file-width="1200" height="12" src="https://upload.wikimedia.org/wikipedia/en/thumb/a/ae/Flag_of_the_United_Kingdom.svg/23px-Flag_of_the_United_Kingdom.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a>, 25 May 2023 (resolution passed by the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_the_United_Kingdom" title="House of Commons of the United Kingdom">House of Commons</a>)
<ul><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="480" data-file-width="800" height="14" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Flag_of_Wales.svg/23px-Flag_of_Wales.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Wales" title="Wales">Wales</a>, 25 October 2023</li></ul></li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="650" data-file-width="1235" height="12" src="https://upload.wikimedia.org/wikipedia/en/thumb/a/a4/Flag_of_the_United_States.svg/23px-Flag_of_the_United_States.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/United_States" title="United States">United States</a>, 11 December 2018 (resolution passed by the <a href="https://en.wikipedia.org/wiki/United_States_House_of_Representatives" title="United States House of Representatives">House of Representatives</a>; on 4 October 2018 resolution passed by the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/US_Senate" title="US Senate">Senate</a>)</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="1000" data-file-width="1000" height="16" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Flag_of_the_Vatican_City_%282023%E2%80%93present%29.svg/16px-Flag_of_the_Vatican_City_%282023%E2%80%93present%29.svg.png" width="16" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Vatican_City" title="Vatican City">Vatican City</a>, 2 April 2004</li></ul></div>
<p>Other political bodies whose legislatures have passed a resolution recognizing Holodomor as a genocide:
</p>
<ul><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="540" data-file-width="810" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Flag_of_Europe.svg/23px-Flag_of_Europe.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/European_Union" title="European Union">EU</a>, 15 December 2022</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="410" data-file-width="700" height="13" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_Council_of_Europe.svg/23px-Flag_of_the_Council_of_Europe.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Council_of_Europe" title="Council of Europe">Parliamentary Assembly of the Council of Europe</a>, 12 October 2023</li><li><span class="flagicon"><span class="mw-image-border"><span><img alt="" class="mw-file-element" data-file-height="700" data-file-width="1100" height="15" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Flag_of_Chechen_Republic_of_Ichkeria.svg/23px-Flag_of_Chechen_Republic_of_Ichkeria.svg.png" width="23" /></span></span> </span><a href="https://en.wikipedia.org/wiki/Chechen_Republic_of_Ichkeria" title="Chechen Republic of Ichkeria">Chechen Republic of Ichkeria</a> (government in exile), 19 April 2023</li></ul>
<p>Many countries have signed declarations in statements at the <a href="https://en.wikipedia.org/wiki/United_Nations_General_Assembly" title="United Nations General Assembly">United Nations General Assembly</a>
affirming that the Holodomor was as a "national tragedy of the
Ukrainian people" caused by the "cruel actions and policies of the
totalitarian regime". Similar statements were passed as resolutions by international organizations such as the <a href="https://en.wikipedia.org/wiki/European_Parliament" title="European Parliament">European Parliament</a>, the <a href="https://en.wikipedia.org/wiki/Parliamentary_Assembly_of_the_Council_of_Europe" title="Parliamentary Assembly of the Council of Europe">Parliamentary Assembly of the Council of Europe</a> (PACE), the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Organization_for_Security_and_Cooperation_in_Europe" title="Organization for Security and Cooperation in Europe">Organization for Security and Cooperation in Europe</a> (OSCE and the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/United_Nations_Organization_for_Education,_Science_and_Culture" title="United Nations Organization for Education, Science and Culture">United Nations Organization for Education, Science and Culture</a> (UNESCO).
</p>
Countries to have signed declarations for the <a href="https://en.wikipedia.org/wiki/United_Nations" title="United Nations">United Nations</a> on the Holodomorinclude <a href="https://en.wikipedia.org/wiki/Albania" title="Albania">Albania</a>, Argentina, Australia, <a href="https://en.wikipedia.org/wiki/Austria" title="Austria">Austria</a>, Azerbaijan, Belgium, <a href="https://en.wikipedia.org/wiki/Bulgaria" title="Bulgaria">Bulgaria</a>, Canada, <a href="https://en.wikipedia.org/wiki/Chile" title="Chile">Chile</a>, Colombia, <a href="https://en.wikipedia.org/wiki/Czech_Republic" title="Czech Republic">Czechia</a>, <a href="https://en.wikipedia.org/wiki/Croatia" title="Croatia">Croati</a>a, <a href="https://en.wikipedia.org/wiki/Denmark" title="Denmark">Denmark</a>, Ecuador, Estonia, <a href="https://en.wikipedia.org/wiki/Finland" title="Finland">Finland</a>, <a href="https://en.wikipedia.org/wiki/France" title="France">France</a>, Georgia, Hungary, <a href="https://en.wikipedia.org/wiki/Iceland" title="Iceland">Iceland</a>, <a href="https://en.wikipedia.org/wiki/Republic_of_Ireland" title="Republic of Ireland">Ireland</a>, <a href="https://en.wikipedia.org/wiki/Israel" title="Israel">Israel</a>, Latvia, <a href="https://en.wikipedia.org/wiki/Liechtenstein" title="Liechtenstein">Liechtenstein</a>, Lithuania, <a href="https://en.wikipedia.org/wiki/Luxembourg" title="Luxembourg">Luxembourg</a>, Mexico, Moldova, <a href="https://en.wikipedia.org/wiki/Monaco" title="Monaco">Monaco</a>, <a href="https://en.wikipedia.org/wiki/Montenegro" title="Montenegro">Montenegro</a>, Paraguay, Peru, Poland, Portugal, <a href="https://en.wikipedia.org/wiki/Slovakia" title="Slovakia">Slovakia</a>, <a href="https://en.wikipedia.org/wiki/Spain" title="Spain">Spain</a>, Ukraine, and the United States.</div></div>
<h3><span class="mw-headline" id="Khojaly_massacre">Khojaly massacre</span></h3><div class="excerpt-block"><div class="excerpt">
The <a href="https://en.wikipedia.org/wiki/Khojaly_massacre" title="Khojaly massacre">Khojaly massacre</a> was the mass killing of at least 161 <a href="https://en.wikipedia.org/wiki/Azerbaijanis" title="Azerbaijanis">Azerbaijani</a> civilians by <a href="https://en.wikipedia.org/wiki/Armenians" title="Armenians">Armenian</a> forces and the <a href="https://en.wikipedia.org/wiki/366th_Guards_Motor_Rifle_Regiment" title="366th Guards Motor Rifle Regiment">366th CIS regiment</a> in the town of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Khojaly_(town)" title="Khojaly (town)">Khojaly</a> on 25 February 1992 It has been recognized and commemorated by acts adopted in fifteen countries and in 28 <a href="https://en.wikipedia.org/wiki/United_States" title="United States">U.S.</a> states, Historian <a href="https://en.wikipedia.org/wiki/Donald_Bloxham" title="Donald Bloxham">Donald Bloxham</a>
states that it is inaccurate to see the Khojaly massacre as a genocide,
stating that it is a "misleading deployment of the term in pursuit of
nationalist
goals".
</div></div>
<h3><span class="mw-headline" id="Romani_genocide">Romani genocide</span></h3><div class="excerpt-block"><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note"><br /></div><div class="excerpt">
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Berlin_Sinta_and_Roma_memorial_2014-2.jpg"><img class="mw-file-element" data-file-height="3456" data-file-width="5184" height="267" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Berlin_Sinta_and_Roma_memorial_2014-2.jpg/220px-Berlin_Sinta_and_Roma_memorial_2014-2.jpg" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Memorial_to_the_Sinti_and_Roma_Victims_of_National_Socialism" title="Memorial to the Sinti and Roma Victims of National Socialism">Memorial to the Sinti and Roma Victims of the Nazis</a> in Berlin, Germany</figcaption></figure>
<p>The German government paid <a href="https://en.wikipedia.org/wiki/War_reparations" title="War reparations">war reparations</a>
to Jewish survivors of the Holocaust, but not to the Romani. There were
"never any consultations at Nuremberg or any other international
conference as to whether the Sinti and Roma were entitled like the Jews
to reparations."<sup class="reference" id="cite_ref-342"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-342">[]</a></sup>
The Interior Ministry of Wuerttemberg argued that "Gypsies [were]
persecuted under the Nazis not for any racial reason but because of an
asocial and criminal record". When on trial for his leadership of <a href="https://en.wikipedia.org/wiki/Einsatzgruppen" title="Einsatzgruppen">Einsatzgruppen</a> in the USSR, <a href="https://en.wikipedia.org/wiki/Otto_Ohlendorf" title="Otto Ohlendorf">Otto Ohlendorf</a> cited the massacres of Roma people during the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Thirty_Years_War" title="Thirty Years War">Thirty Years War</a> as a historical precedent.
</p><p>The <a href="https://en.wikipedia.org/wiki/European_Roma_Rights_Centre" title="European Roma Rights Centre">European Roma Rights Centre</a> in 2017 gave more details of the chronology of recognition and reparations:
</p>
<blockquote class="templatequote"><p> After World War II Roma were also
excluded from the right to restitution, because Federal German
authorities denied that Roma were persecued due to racist reasons. After
a small step in this direction in 1963, restitutions became possible in
small amounts only in 1979, when the West German Federal Parliament
declared that the Nazi persecution of Roma was based on <a href="https://en.wikipedia.org/wiki/Racism" title="Racism">racial grounds</a>
and Roma survivors were allowed to claim for restitution in a form of a
onetime payment. The official acceptance of the Porajmos as genocide by
the Federal Republic of Germany followed only in 1982 with a speech by
Chancelor Helmut Schmidt. In August 2016, an agreement between the
German Ministry for Finance and the Foreign Ministry of the Czech
Republic decided on compensation for survivors of the Porajmos in the
Czech Republic. This agreement, which will give 2,500 EUR to each of the
handful of survivors, was greeted as a symbolic acknowledgment, but
also criticised for its delay and the low amount awarded. However, this
agreement has already led to renewed claims from Romani victims from the
former Yugoslavia and other regions of 'romocide'. </p></blockquote>
<p>In the historiography of East Germany (GDR), the persecution of Sinti
and Roma under National Socialism was largely taboo. The German
historian Anne-Kathleen Tillack-Graf states that in the GDR, Sinti and
Roma were not mentioned as concentration camp prisoners during the
official commemorations of the liberation at the three national memorial
sites <a href="https://en.wikipedia.org/wiki/Buchenwald_concentration_camp" title="Buchenwald concentration camp">Buchenwald</a>, <a href="https://en.wikipedia.org/wiki/Sachsenhausen_concentration_camp" title="Sachsenhausen concentration camp">Sachsenhausen</a>, and <a href="https://en.wikipedia.org/wiki/Ravensbr%C3%BCck_concentration_camp" title="Ravensbrück concentration camp">Ravensbrück</a>, just like <a href="https://en.wikipedia.org/wiki/Persecution_of_homosexuals_in_Nazi_Germany" title="Persecution of homosexuals in Nazi Germany">homosexuals</a>, <a href="https://en.wikipedia.org/wiki/Persecution_of_Jehovah%27s_Witnesses_in_Nazi_Germany" title="Persecution of Jehovah's Witnesses in Nazi Germany">Jehovah's Witnesses</a> and <a href="https://en.wikipedia.org/wiki/Black_triangle_(badge)" title="Black triangle (badge)">asocial detainees</a>. West Germany recognised the genocide of the Roma in 1982, and since then the Porajmos has been increasingly recognized as a genocide committed simultaneously with the Shoah. The American historian <a href="https://en.wikipedia.org/wiki/Sybil_Milton" title="Sybil Milton">Sybil Milton</a> wrote several articles arguing that the Porajmos deserved recognition as part of the Holocaust. In Switzerland, a committee of experts investigated the policy of the Swiss government during the Porajmos.
</p><p>Formal recognition and commemoration of the Roma persecution by
the Nazis have been difficult in practical terms due to the lack of
significant <a href="https://en.wikipedia.org/wiki/Collective_memory" title="Collective memory">collective memory</a>
and documentation of the Porajmos among the Roma. This results from
both of their tradition of oral history and illiteracy, heightened by
widespread poverty and continuing discrimination that has forced some
Roma out of state schools. One <a href="https://en.wikipedia.org/wiki/UNESCO" title="UNESCO">UNESCO</a>
report of Roma in Romania showed that only 40% of Roma children are
enrolled in primary school, compared to the national average of 93%. Of those enrolled, only 30% of Roma children go on to complete primary school.
</p><p>Nico Fortuna, a sociologist and Roma activist, explained the distinction between Jewish collective memory of the <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Shoah" title="Shoah">Shoah</a></i> and the Roma experience:
</p>
<blockquote class="templatequote"><p>There is a difference between the
Jewish and Roma deportees ... The Jews were shocked and can remember the
year, date and time it happened. The Roma shrugged it off. They said,
"Of course I was deported. I'm Roma; these things happen to a Roma." The
Roma mentality is different from the Jewish mentality. For example, a
Roma came to me and asked, "Why do you care so much about these
deportations? Your family was not deported." I went, "I care as a Roma"
and the guy said back, "I do not care because my family were brave,
proud Roma that were not deported."<br />
For the Jews it was total and everyone knew this—from bankers to
pawnbrokers. For the Roma it was selective and not comprehensive. The
Roma were only exterminated in a few parts of Europe such as Poland, the
Netherlands, Germany and France. In Romania and much of the Balkans,
only nomadic Roma and social outcast Roma were deported. This matters
and influences the Roma mentality.</p></blockquote>
Ian Hancock has also observed a reluctance among Roma to acknowledge
their victimization by the Third Reich. The Roma "are traditionally not
disposed to keeping alive the terrible memories from their
history—nostalgia is a luxury for others".
The effects of the illiteracy, the lack of social institutions, and the
rampant discrimination faced by Roma in Europe today have produced a
people who, according to Fortuna, lack a "national consciousness ... and
historical memory of the Holocaust because there is no Roma elite."</div></div>
<h3><span class="mw-headline" id="Persecution_of_Uyghurs_in_China">Persecution of Uyghurs in China</span></h3><div class="hatnote navigation-not-searchable dablink excerpt-hat selfref" role="note">This section is an excerpt from <a href="https://en.wikipedia.org/wiki/Persecution_of_Uyghurs_in_China#Genocide" title="Persecution of Uyghurs in China">Persecution of Uyghurs in China § Genocide</a>.<span class="mw-editsection-like plainlinks"><span class="mw-editsection-bracket">[</span><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Persecution_of_Uyghurs_in_China&action=edit#Genocide">edit</a><span class="mw-editsection-bracket">]</span></span></div><div class="excerpt">
<p>In April 2019, <a href="https://en.wikipedia.org/wiki/Cornell_University" title="Cornell University">Cornell University</a> anthropologist Magnus Fiskesjö wrote in <i><a href="https://en.wikipedia.org/wiki/Inside_Higher_Ed" title="Inside Higher Ed">Inside Higher Ed</a></i>
that mass arrests of ethnic minority academics and intellectuals in
Xinjiang indicated that "the Chinese regime's current campaign against
the native Uighur, Kazakh and other peoples is already a genocide." Later, in 2020, Fiskejö wrote in academic journal <i>Monde Chinois</i>
that "[t]he evidence for genocide is thus already massive, and must, at
the very least, be regarded as sufficient for prosecution under
international law... the number of competent authorities around the
world concurring that this is indeed genocide are increasing."
</p><p>In June 2020, after an <a href="https://en.wikipedia.org/wiki/Associated_Press" title="Associated Press">Associated Press</a>
investigation found that Uyghurs were being subjected to mass forced
sterilizations and forced abortions in Xinjiang, scholars increasingly
have referred to the abuses in Xinjiang as a genocide.
</p><p>In July 2020, Zenz said an interview with <a href="https://en.wikipedia.org/wiki/NPR" title="NPR">National Public Radio</a>
(NPR) that he had previously argued that the actions of the Chinese
government are a cultural genocide, not a "literal genocide", but that
one of the five criteria from the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>
was satisfied by more recent developments concerning the suppression of
birth rates so "we do need to probably call it a genocide". The same month, the last colonial governor of <a href="https://en.wikipedia.org/wiki/British_Hong_Kong" title="British Hong Kong">British Hong Kong</a>, <a href="https://en.wikipedia.org/wiki/Chris_Patten" title="Chris Patten">Chris Patten</a>,
said that the "birth control campaign" was "arguably something that
comes within the terms of the UN views on sorts of genocide".
</p><p>Although China is not a member of the <a href="https://en.wikipedia.org/wiki/International_Criminal_Court" title="International Criminal Court">International Criminal Court</a>, on 6 July 2020 the self-proclaimed <a class="mw-redirect" href="https://en.wikipedia.org/wiki/East_Turkistan_Government-in-Exile" title="East Turkistan Government-in-Exile">East Turkistan Government-in-Exile</a> and the <a href="https://en.wikipedia.org/wiki/East_Turkistan_National_Awakening_Movement" title="East Turkistan National Awakening Movement">East Turkistan National Awakening Movement</a> filed <a class="mw-redirect" href="https://en.wikipedia.org/wiki/East_Turkistan_Government-in-Exile#International_Criminal_Court_case" title="East Turkistan Government-in-Exile">a complaint with the ICC</a> calling for it to investigate PRC officials for crimes against Uyghurs including allegations of genocide.
The ICC responded in December 2020 and "asked for more evidence before
it will be willing to open an investigation into claims of genocide
against Uighur people by China, but has said it will keep the file open
for such further evidence to be submitted."
</p><p>An August 2020 <i><a href="https://en.wikipedia.org/wiki/Quartz_(publication)" title="Quartz (publication)">Quartz</a></i>
article reported that some scholars hesitate to label the human rights
abuses in Xinjiang as a "full-blown genocide", preferring the term
"cultural genocide", but that increasingly many experts were calling
them "crimes against humanity" or "genocide". In August 2020 the spokesperson for <a href="https://en.wikipedia.org/wiki/Joe_Biden" title="Joe Biden">Joe Biden</a>'s presidential campaign described China's actions as genocide.
</p><p>In October 2020, the <a href="https://en.wikipedia.org/wiki/United_States_Senate" title="United States Senate">U.S. Senate</a> introduced a bipartisan resolution designating the <a href="https://en.wikipedia.org/wiki/Human_rights#Violations" title="Human rights">human rights abuses</a> perpetrated by the Chinese government against the Uyghur people and other ethnic minorities in Xinjiang as genocide. Around the same time, the <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_Canada" title="House of Commons of Canada">House of Commons of Canada</a> issued a statement that its Subcommittee on International Human Rights of the <a href="https://en.wikipedia.org/wiki/Canadian_House_of_Commons_Standing_Committee_on_Foreign_Affairs_and_International_Development" title="Canadian House of Commons Standing Committee on Foreign Affairs and International Development">Standing Committee on Foreign Affairs and International Development</a> was persuaded that the <a href="https://en.wikipedia.org/wiki/Chinese_Communist_Party" title="Chinese Communist Party">Chinese Communist Party</a>'s actions in Xinjiang constitute genocide as laid out in the Genocide Convention. The 2020 annual report by the <a href="https://en.wikipedia.org/wiki/Congressional-Executive_Commission_on_China" title="Congressional-Executive Commission on China">Congressional-Executive Commission on China</a> referred to the Chinese government's treatment of Uyghurs as "crimes against humanity and possibly genocide."
</p><p>In January 2021, U.S. secretary of state <a href="https://en.wikipedia.org/wiki/Mike_Pompeo" title="Mike Pompeo">Mike Pompeo</a> officially declared that China was committing genocide against the Uyghurs and other ethnic minorities living in Xinjiang.
This declaration, which came in the final hours of the Trump
administration, had not been made earlier due to a worry that it could
disrupt trade talks between the US and China. On the allegations of
crimes against humanity Pompeo asserted that "These crimes are ongoing
and include: the arbitrary imprisonment or other severe deprivation of
physical liberty of more than one million civilians, forced
sterilization, torture of a large number of those arbitrarily detained,
forced labor and the imposition of draconian restrictions on freedom of
religion or belief, freedom of expression and freedom of movement."
</p><p>On 19 January 2021, incoming U.S. president Joe Biden's <a href="https://en.wikipedia.org/wiki/United_States_Secretary_of_State" title="United States Secretary of State">secretary of state</a> nominee <a href="https://en.wikipedia.org/wiki/Antony_Blinken" title="Antony Blinken">Antony Blinken</a>
was asked during his confirmation hearings whether he agreed with
Pompeo's conclusion that the CCP had committed genocide against the
Uyghurs, he contended "That would be my judgment as well." During her confirmation hearings Joe Biden's nominee to be the US ambassador to the United Nations <a href="https://en.wikipedia.org/wiki/Linda_Thomas-Greenfield" title="Linda Thomas-Greenfield">Linda Thomas-Greenfield</a>
stated that she believed what was currently happening in Xinjiang was a
genocide, adding "I lived through and experienced and witnessed a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genocide_in_Rwanda" title="Genocide in Rwanda">genocide in Rwanda</a>."
</p><p>The US designation was followed by <a href="https://en.wikipedia.org/wiki/House_of_Commons_of_Canada" title="House of Commons of Canada">Canada's House of Commons</a> and the <a href="https://en.wikipedia.org/wiki/States_General_of_the_Netherlands" title="States General of the Netherlands">Dutch parliament</a>, each passing a <a href="https://en.wikipedia.org/wiki/Non-binding_resolution" title="Non-binding resolution">non-binding motion</a> in February 2021 to recognize China's actions as genocide.
</p><p>In January 2021, the <a href="https://en.wikipedia.org/wiki/United_States_Holocaust_Memorial_Museum" title="United States Holocaust Memorial Museum">United States Holocaust Memorial Museum</a>
initially stated that, "[t]here is a reasonable basis to believe that
the government of China is committing crimes against humanity."
In November 2021, the United States Holocaust Memorial Museum revised
its stance to state that the "Chinese government may be committing
genocide against the Uyghurs."
</p><p>In February 2021, a report released by the <a href="https://en.wikipedia.org/wiki/Essex_Court_Chambers" title="Essex Court Chambers">Essex Court Chambers</a>
concluded that "there is a very credible case that acts carried out by
the Chinese government against the Uighur people in Xinjiang Uighur
Autonomous Region amount to crimes against humanity and the crime of
genocide, and describes how the minority group has been subject to
"enslavement, torture, rape, enforced sterilisation and persecution."
"Victims have been "forced to remain in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Stress_positions" title="Stress positions">stress positions</a>
for an extended period of time, beaten, deprived of food, shackled and
blindfolded", it said. The legal team stated that they had seen
"prolific credible evidence" of sterilisation procedures carried out on
women, including forced abortions, saying the human rights abuses
"clearly constitute a form of genocidal conduct".<sup class="reference" id="cite_ref-Persecution_of_Uyghurs_in_China_url_377-0"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-Persecution_of_Uyghurs_in_China_url-377">[369]</a></sup>
</p><p>On 13 February 2021, <i><a href="https://en.wikipedia.org/wiki/The_Economist" title="The Economist">The Economist</a></i> wrote that while China's treatment and persecution of Uyghurs is "horrific" and a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Crime_against_humanity" title="Crime against humanity">crime against humanity</a>, "genocide" is the wrong word for China's actions due to China not engaging in mass murder.
</p><p>According to a March 2021 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Newlines_Institute" title="Newlines Institute">Newlines Institute</a> report that was written by over 50 global China, genocide, and international law experts, the Chinese government breached every article in the <a href="https://en.wikipedia.org/wiki/Genocide_Convention" title="Genocide Convention">Genocide Convention</a>,
writing, "China's long-established, publicly and repeatedly declared,
specifically targeted, systematically implemented, and fully resourced
policy and practice toward the Uyghur group is inseparable from 'the
intent to destroy in whole or in part' the Uyghur group as such."<sup class="reference" id="cite_ref-Persecution_of_Uyghurs_in_China_Davidson-2021_381-0"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-Persecution_of_Uyghurs_in_China_Davidson-2021-381">[373]</a></sup><sup class="reference" id="cite_ref-Persecution_of_Uyghurs_in_China_urlUyghurs_in_Australia_call_for_genocide_declaration_in_wake_of_report_into_Chinas_Xinjiang_region_policies_-_ABC_News_382-0"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-Persecution_of_Uyghurs_in_China_urlUyghurs_in_Australia_call_for_genocide_declaration_in_wake_of_report_into_Chinas_Xinjiang_region_policies_-_ABC_News-382">[374]</a></sup><sup class="reference" id="cite_ref-383"><a href="https://en.wikipedia.org/wiki/Genocide_recognition_politics#cite_note-383">[375]</a></sup>
The report cited credible reports of mass deaths under the mass
internment drive, while Uighur leaders were selectively sentenced to
death or sentenced to long-term imprisonment. "Uyghurs are suffering
from systematic torture and cruel, inhumane, and degrading treatment,
including rape, sexual abuse, and public humiliation, both inside and
outside the camps", the report stated. The report argued that these
policies are directly orchestrated by the highest levels of state,
including Xi and the top officials of the Chinese Communist Party in
Xinjiang.
It also reported that the Chinese government gave explicit orders to
"eradicate tumours", "wipe them out completely", "destroy them root and
branch", "round up everyone", and "show absolutely no mercy", in regards
to Uyghurs,
and that camp guards reportedly follow orders to uphold the system in
place until "Kazakhs, Uyghurs, and other Muslim nationalities, would
disappear...until all Muslim nationalities would be extinct".
According to the report "Internment camps contain designated
"interrogation rooms" where Uyghur detainees are subjected to consistent
and brutal torture methods, including beatings with metal prods,
electric shocks, and whips."
</p><p>In June 2021, the Canadian Anthropology Society issued a
statement on Xinjiang in which the organization stated, "expert
testimony and witnessing, and irrefutable evidence from the Chinese
Government's own satellite imagery, documents, and eyewitness reports,
overwhelmingly confirms the scale of the genocide."
</p><p>In August 2022, the U.S. State Department published a report <i>PRC Efforts to Manipulate Global Public Opinion on Xinjiang</i>
on the Chinese government's global efforts "to discredit independent
sources that report ongoing genocide and crimes against humanity" in
Xinjiang.
</p><p>A 2023 academic book by political theorists Alain Brossat and
Juan Alberto Ruiz Casado labeled the accusation of genocide as
unsubstantiated.
They described the information used to apply the label as misleading
and coming "exclusively from a few sources, for the most part
overwhelmingly and openly partisan in their anti-China crusade"; they
especially criticize Adrian Zenz's 2018 detainee study and 2019
sterilization study as "academically flimsy" and containing misleading
or directly false claims, respectively.
</p>
Academics Steve Tsang and Olivia Cheung write that their research has
found no evidence that Xi Jinping advocates genocide against Uyghurs. Tsang and Cheung conclude that China's policies subordinate identity
based on culture, religion, or minority language in an effort to
establish a national identity based on Han heritage, language, and Xi
Jinping Thought.</div>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-31360166693465760992024-03-16T14:25:00.002-04:002024-03-16T14:25:55.956-04:00Ideal solution<p></p><div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia<br /><a href="https://en.wikipedia.org/wiki/Ideal_solution">https://en.wikipedia.org/wiki/Ideal_solution</a><br /></div>
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<p>In <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, an <b>ideal solution</b> or <b>ideal mixture</b> is a <a href="https://en.wikipedia.org/wiki/Solution_(chemistry)" title="Solution (chemistry)">solution</a> that exhibits thermodynamic properties analogous to those of a mixture of <a href="https://en.wikipedia.org/wiki/Ideal_gas" title="Ideal gas">ideal gases</a>. The <a href="https://en.wikipedia.org/wiki/Enthalpy_of_mixing" title="Enthalpy of mixing">enthalpy of mixing</a> is zero
as is the volume change on mixing by definition; the closer to zero the
enthalpy of mixing is, the more "ideal" the behavior of the solution
becomes. The <a href="https://en.wikipedia.org/wiki/Vapor_pressure" title="Vapor pressure">vapor pressures</a> of the solvent and solute obey <a href="https://en.wikipedia.org/wiki/Raoult%27s_law" title="Raoult's law">Raoult's law</a> and <a href="https://en.wikipedia.org/wiki/Henry%27s_law" title="Henry's law">Henry's law</a>, respectively, and the <a href="https://en.wikipedia.org/wiki/Activity_coefficient" title="Activity coefficient">activity coefficient</a> (which measures deviation from ideality) is equal to one for each component.
</p><p>The concept of an ideal solution is fundamental to <a href="https://en.wikipedia.org/wiki/Chemical_thermodynamics" title="Chemical thermodynamics">chemical thermodynamics</a> and its applications, such as the explanation of <a href="https://en.wikipedia.org/wiki/Colligative_properties" title="Colligative properties">colligative properties</a>.
</p>
<h2><span class="mw-headline" id="Physical_origin">Physical origin</span></h2></div></div></div><p>Ideality of solutions is analogous to <a href="https://en.wikipedia.org/wiki/Ideal_gas" title="Ideal gas">ideality for gases</a>,
with the important difference that intermolecular interactions in
liquids are strong and cannot simply be neglected as they can for ideal
gases. Instead we assume that the mean strength of the <a href="https://en.wikipedia.org/wiki/Intermolecular_force" title="Intermolecular force">interactions</a> are the same between all the molecules of the solution.
</p><p>More formally, for a mix of molecules of A and B, then the interactions between unlike neighbors (<i>U</i><sub>AB</sub>) and like neighbors <i>U</i><sub>AA</sub> and <i>U</i><sub>BB</sub> must be of the same average strength, i.e., 2 <i>U</i><sub>AB</sub> = <i>U</i><sub>AA</sub> + U<sub>BB</sub>
and the longer-range interactions must be nil (or at least
indistinguishable). If the molecular forces are the same between AA, AB
and BB, i.e., <i>U</i><sub>AB</sub> = <i>U</i><sub>AA</sub> = <i>U</i><sub>BB</sub>, then the solution is automatically ideal.
</p><p>If the molecules are almost identical chemically, e.g., <a class="mw-redirect" href="https://en.wikipedia.org/wiki/N-butanol" title="N-butanol">1-butanol</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/2-butanol" title="2-butanol">2-butanol</a>,
then the solution will be almost ideal. Since the interaction energies
between A and B are almost equal, it follows that there is only a very
small overall energy (enthalpy) change when the substances are mixed.
The more dissimilar the nature of A and B, the more strongly the
solution is expected to deviate from ideality.
</p>
<h2><span class="mw-headline" id="Formal_definition">Formal definition</span></h2><p>Different
related definitions of an ideal solution have been proposed. The
simplest definition is that an ideal solution is a solution for which
each component obeys <a href="https://en.wikipedia.org/wiki/Raoult%27s_law" title="Raoult's law">Raoult's law</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msubsup>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p_{i}=x_{i}p_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/77c8ce2e0ddf54bab0488920e31e544ef263d61e" style="height: 2.843ex; margin-left: -0.089ex; vertical-align: -1.005ex; width: 9.51ex;" /></span> for all compositions. Here <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5bab39399bf5424f25d957cdc57c84a0622626d2" style="height: 2.009ex; margin-left: -0.089ex; vertical-align: -0.671ex; width: 2.059ex;" /></span> is the <a href="https://en.wikipedia.org/wiki/Vapor_pressure" title="Vapor pressure">vapor pressure</a> of component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> above the solution, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e87000dd6142b81d041896a30fe58f0c3acb2158" style="height: 2.009ex; vertical-align: -0.671ex; width: 2.129ex;" /></span> is its <a href="https://en.wikipedia.org/wiki/Mole_fraction" title="Mole fraction">mole fraction</a> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7a639fd7524a9d84c54a8f64a64afcdfa348eec4" style="height: 2.843ex; margin-left: -0.089ex; vertical-align: -1.005ex; width: 2.313ex;" /></span> is the vapor pressure of the pure substance <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> at the same temperature.
</p><p>This definition depends on vapor pressure, which is a directly
measurable property, at least for volatile components. The thermodynamic
properties may then be obtained from the <a href="https://en.wikipedia.org/wiki/Chemical_potential" title="Chemical potential">chemical potential</a> μ (which is the <a href="https://en.wikipedia.org/wiki/Partial_molar_property" title="Partial molar property">partial molar</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Gibbs_energy" title="Gibbs energy">Gibbs energy</a> <i>g</i>) of each component. If the vapor is an ideal gas,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>μ</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>g</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mi>g</mi>
<mrow>
<mrow>
<mi mathvariant="normal">u</mi>
</mrow>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
<mo stretchy="false">)</mo>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu (T,p_{i})=g(T,p_{i})=g^{\mathrm {u} }(T,p^{u})+RT\ln {\frac {p_{i}}{p^{u}}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b34422ea6d3af3f5aa21a61c61c4a94ffeca4e87" style="height: 5.343ex; vertical-align: -2.338ex; width: 43.477ex;" /></span></dd></dl>
<p>The reference pressure <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p^{u}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2d977c5fbb8474380c7ea8f706e5178595a7b5e3" style="height: 2.676ex; margin-left: -0.089ex; vertical-align: -0.671ex; width: 2.431ex;" /></span> may be taken as <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>P</mi>
<mrow>
<mi>o</mi>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle P^{o}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/22e3d4f9c11df84b333320b0d688e48c2450d0e3" style="height: 2.343ex; vertical-align: -0.338ex; width: 2.851ex;" /></span> = 1 bar, or as the pressure of the mix, whichever is simpler.
</p><p>On substituting the value of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5bab39399bf5424f25d957cdc57c84a0622626d2" style="height: 2.009ex; margin-left: -0.089ex; vertical-align: -0.671ex; width: 2.059ex;" /></span> from Raoult's law,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>μ</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mi>g</mi>
<mrow>
<mrow>
<mi mathvariant="normal">u</mi>
</mrow>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
<mo stretchy="false">)</mo>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<msubsup>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msubsup>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu (T,p_{i})=g^{\mathrm {u} }(T,p^{u})+RT\ln {\frac {p_{i}^{*}}{p^{u}}}+RT\ln x_{i}=\mu _{i}^{*}+RT\ln x_{i}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/efb2be647c9f228ffb7fd68ce7805f801f211b03" style="height: 6.009ex; vertical-align: -2.338ex; width: 60.535ex;" /></span></dd></dl>
<p>This equation for the chemical potential can be used as an alternate definition for an ideal solution.
</p><p>However, the vapor above the solution may not actually behave as a
mixture of ideal gases. Some authors therefore define an ideal solution
as one for which each component obeys the fugacity analogue of Raoult's
law <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msubsup>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle f_{i}=x_{i}f_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1132038d5334ed40a1a094e4f2e74ef79bc4df6d" style="height: 2.843ex; vertical-align: -1.005ex; width: 9.541ex;" /></span>. Here <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle f_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/65da883ca3d16b461e46c94777b0d9c4aa010e79" style="height: 2.509ex; vertical-align: -0.671ex; width: 1.939ex;" /></span> is the <a href="https://en.wikipedia.org/wiki/Fugacity" title="Fugacity">fugacity</a> of component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> in solution and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle f_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7ed4795cb8f8175b2b7a0f450d98990fe1d46fcf" style="height: 2.843ex; vertical-align: -1.005ex; width: 2.375ex;" /></span> is the fugacity of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> as a pure substance. Since the fugacity is defined by the equation
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>μ</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>g</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mi>g</mi>
<mrow>
<mrow>
<mi mathvariant="normal">u</mi>
</mrow>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
<mo stretchy="false">)</mo>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<msub>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu (T,P)=g(T,P)=g^{\mathrm {u} }(T,p^{u})+RT\ln {\frac {f_{i}}{p^{u}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/592d98a477674b372cf44b1360ea6e4ba7628422" style="height: 5.843ex; vertical-align: -2.338ex; width: 42.383ex;" /></span></dd></dl>
<p>this definition leads to ideal values of the chemical potential and
other thermodynamic properties even when the component vapors above the
solution are not ideal gases. An equivalent statement uses thermodynamic
<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_(chemistry)" title="Activity (chemistry)">activity</a> instead of fugacity.
</p>
<h2><span class="mw-headline" id="Thermodynamic_properties">Thermodynamic properties</span></h2><h3><span class="mw-headline" id="Volume">Volume</span></h3><p>If we differentiate this last equation with respect to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>p</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle p}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/81eac1e205430d1f40810df36a0edffdc367af36" style="height: 2.009ex; margin-left: -0.089ex; vertical-align: -0.671ex; width: 1.259ex;" /></span> at <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>T</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle T}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ec7200acd984a1d3a3d7dc455e262fbe54f7f6e0" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.636ex;" /></span> constant we get:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>g</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>P</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>T</mi>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>ln</mi>
<mo></mo>
<mi>f</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>P</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>T</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial g(T,P)}{\partial P}}\right)_{T}=RT\left({\frac {\partial \ln f}{\partial P}}\right)_{T}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/975a6abf868c639b0bc1ad9f1854943492b7223b" style="height: 6.343ex; vertical-align: -2.505ex; width: 32.408ex;" /></span></dd></dl>
<p>Since we know from the Gibbs potential equation that:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>g</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>P</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>T</mi>
</mrow>
</msub>
<mo>=</mo>
<mi>v</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial g(T,P)}{\partial P}}\right)_{T}=v}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5c9e16cb1d613f1c7a3bddaf4659fba3abf773fb" style="height: 6.343ex; vertical-align: -2.505ex; width: 18.532ex;" /></span></dd></dl>
<p>with the molar volume <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>v</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle v}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e07b00e7fc0847fbd16391c778d65bc25c452597" style="height: 1.676ex; vertical-align: -0.338ex; width: 1.128ex;" /></span>, these last two equations put together give:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>ln</mi>
<mo></mo>
<mi>f</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>P</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>T</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mi>v</mi>
<mrow>
<mi>R</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial \ln f}{\partial P}}\right)_{T}={\frac {v}{RT}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6e068884b4a876049bf1fc9f07c7fed13eb05c99" style="height: 6.176ex; vertical-align: -2.505ex; width: 18.938ex;" /></span></dd></dl>
<p>Since all this, done as a pure substance, is valid in an ideal mix just adding the subscript <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> to all the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Intensive_variable" title="Intensive variable">intensive variables</a> and changing <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>v</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle v}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e07b00e7fc0847fbd16391c778d65bc25c452597" style="height: 1.676ex; vertical-align: -0.338ex; width: 1.128ex;" /></span> to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>v</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {v_{i}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/98487fe462ce101bf156023e16b0cecd54e8d5de" style="height: 2.343ex; vertical-align: -0.671ex; width: 1.927ex;" /></span>, with optional overbar, standing for <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Partial_molar_volume" title="Partial molar volume">partial molar volume</a>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>P</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>T</mi>
<mo>,</mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mover>
<msub>
<mi>v</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
<mrow>
<mi>R</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial \ln f_{i}}{\partial P}}\right)_{T,x_{i}}={\frac {\bar {v_{i}}}{RT}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/457e579d55d9385298ebc261f47efb10344abf61" style="height: 6.509ex; vertical-align: -2.838ex; width: 21.621ex;" /></span></dd></dl>
<p>Applying the first equation of this section to this last equation we find:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>v</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>=</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>v</mi>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle v_{i}^{*}={\bar {v}}_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f276db32ea3a9d2b45782d257a75b8eb4b2b9ab6" style="height: 2.843ex; vertical-align: -1.005ex; width: 7.307ex;" /></span></dd></dl>
<p>which means that the partial molar volumes in an ideal mix are
independent of composition. Consequently, the total volume is the sum of
the volumes of the components in their pure forms:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<msubsup>
<mi>V</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V=\sum _{i}V_{i}^{*}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9782260b9e9424a2b9e0fe08cd258104747255d7" style="height: 5.509ex; vertical-align: -3.005ex; width: 12.246ex;" /></span></dd></dl>
<h3><span class="mw-headline" id="Enthalpy_and_heat_capacity">Enthalpy and heat capacity</span></h3><p>Proceeding in a similar way but taking the derivative with respect to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>T</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle T}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ec7200acd984a1d3a3d7dc455e262fbe54f7f6e0" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.636ex;" /></span> we get a similar result for molar <a href="https://en.wikipedia.org/wiki/Enthalpy" title="Enthalpy">enthalpies</a>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<mrow>
<mi>g</mi>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
<mo>−</mo>
<msup>
<mi>g</mi>
<mrow>
<mrow>
<mi mathvariant="normal">g</mi>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">s</mi>
</mrow>
</mrow>
</msup>
<mo stretchy="false">(</mo>
<mi>T</mi>
<mo>,</mo>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mi>R</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<mi>f</mi>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {g(T,P)-g^{\mathrm {gas} }(T,p^{u})}{RT}}=\ln {\frac {f}{p^{u}}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e5ca894d757993da9167f1b9979630254dd1bea5" style="height: 6.176ex; vertical-align: -2.338ex; width: 30.731ex;" /></span></dd></dl>
<p>Remembering that <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mrow>
<mfrac>
<mi>g</mi>
<mi>T</mi>
</mfrac>
</mrow>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>P</mi>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mrow>
<mfrac>
<mi>h</mi>
<msup>
<mi>T</mi>
<mrow>
<mn>2</mn>
</mrow>
</msup>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial {\frac {g}{T}}}{\partial T}}\right)_{P}=-{\frac {h}{T^{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/61415e89ab77c44addaedb7d790b341f447174df" style="height: 7.676ex; vertical-align: -3.171ex; width: 17.812ex;" /></span> we get:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo>−</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mrow>
<mover>
<msub>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>−</mo>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mrow>
<mi mathvariant="normal">g</mi>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">s</mi>
</mrow>
</mrow>
</msubsup>
</mrow>
<mi>R</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mo>−</mo>
<mrow>
<mfrac>
<mrow>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>−</mo>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mrow>
<mi mathvariant="normal">g</mi>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">s</mi>
</mrow>
</mrow>
</msubsup>
</mrow>
<mi>R</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle -{\frac {{\bar {h_{i}}}-h_{i}^{\mathrm {gas} }}{R}}=-{\frac {h_{i}^{*}-h_{i}^{\mathrm {gas} }}{R}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/960f49c76a7280b816712de077463cc212ccfaa3" style="height: 6.176ex; vertical-align: -2.005ex; width: 26.326ex;" /></span></dd></dl>
<p>which in turn means that <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {h_{i}}}=h_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e1fffb7c001bab329fc088ebe9e7b2a481e71bb5" style="height: 3.176ex; vertical-align: -1.005ex; width: 7.63ex;" /></span> and that the enthalpy of the mix is equal to the sum of its component enthalpies.
</p><p>Since <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>u</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>−</mo>
<mi>p</mi>
<mrow>
<mrow>
<mover>
<msub>
<mi>v</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {u_{i}}}={\bar {h_{i}}}-p{\bar {v_{i}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5875197e971a7514101f2d9003465964b0aff954" style="height: 2.843ex; vertical-align: -0.671ex; width: 13.304ex;" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>u</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>=</mo>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>−</mo>
<mi>p</mi>
<msubsup>
<mi>v</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle u_{i}^{*}=h_{i}^{*}-pv_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/79bd69efc7f844b8fb9844006ae635b780e322be" style="height: 2.843ex; vertical-align: -1.005ex; width: 14.067ex;" /></span>, similarly
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>u</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>u</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle u_{i}^{*}={\bar {u_{i}}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/18727be570988286a9325f9b9d080af16a37f82e" style="height: 2.843ex; vertical-align: -1.005ex; width: 8.259ex;" /></span></dd></dl>
<p>It is also easily verifiable that
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>C</mi>
<mrow>
<mi>p</mi>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>C</mi>
<mrow>
<mi>p</mi>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle C_{pi}^{*}={\bar {C_{pi}}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/fae0ee035b7f3a8912aabd4aa86b90191920c5a4" style="height: 3.676ex; vertical-align: -1.338ex; width: 10.322ex;" /></span></dd></dl>
<h3><span class="mw-headline" id="Entropy_of_mixing">Entropy of mixing</span></h3><p>Finally since
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<msub>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msubsup>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mrow>
<mi mathvariant="normal">g</mi>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">s</mi>
</mrow>
</mrow>
</msubsup>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<msub>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>=</mo>
<msubsup>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mrow>
<mi mathvariant="normal">g</mi>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">s</mi>
</mrow>
</mrow>
</msubsup>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mrow>
<mfrac>
<msubsup>
<mi>f</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<msup>
<mi>p</mi>
<mrow>
<mi>u</mi>
</mrow>
</msup>
</mfrac>
</mrow>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msubsup>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {g_{i}}}=\mu _{i}=g_{i}^{\mathrm {gas} }+RT\ln {\frac {f_{i}}{p^{u}}}=g_{i}^{\mathrm {gas} }+RT\ln {\frac {f_{i}^{*}}{p^{u}}}+RT\ln x_{i}=\mu _{i}^{*}+RT\ln x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/137b5ebe607fa0514c79cf30062eebdb8c46b5f5" style="height: 6.176ex; vertical-align: -2.338ex; width: 72.709ex;" /></span></dd></dl>
<p>we find that
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>g</mi>
<mrow>
<mi>i</mi>
<mo>,</mo>
<mrow>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta g_{i,\mathrm {mix} }=RT\ln x_{i}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f0ef7e746b6ea3b3759e7bd5864318a6aa497596" style="height: 2.843ex; vertical-align: -1.005ex; width: 18.985ex;" /></span></dd></dl>
<p>Since the Gibbs free energy per mole of the mixture <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>G</mi>
<mrow>
<mi>m</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle G_{m}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/99269e24e8109b604cc42cd4d3d94941c0a54aa5" style="height: 2.509ex; vertical-align: -0.671ex; width: 3.502ex;" /></span> is
</p><div class="mwe-math-element"><div class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>G</mi>
<mrow>
<mi>m</mi>
</mrow>
</msub>
<mo>=</mo>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mrow>
<msub>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></div><img alt="{\displaystyle G_{m}=\sum _{i}x_{i}{g_{i}}}" aria-hidden="true" class="mwe-math-fallback-image-display mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/21aec69449c8079c0ea31e01521c109911cdbe40" style="height: 5.509ex; vertical-align: -3.005ex; width: 14.38ex;" /></div>
then
<p></p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>G</mi>
<mrow>
<mrow>
<mi mathvariant="normal">m</mi>
<mo>,</mo>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<mrow>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G_{\mathrm {m,mix} }=RT\sum _{i}{x_{i}\ln x_{i}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/050ce517ee5c0854c365efd01041fd38b1bb5179" style="height: 5.509ex; vertical-align: -3.005ex; width: 26.762ex;" /></span></dd></dl>
<p>At last we can calculate the molar <a href="https://en.wikipedia.org/wiki/Entropy_of_mixing" title="Entropy of mixing">entropy of mixing</a> since
<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>=</mo>
<msubsup>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>−</mo>
<mi>T</mi>
<msubsup>
<mi>s</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle g_{i}^{*}=h_{i}^{*}-Ts_{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2008013b0d5077f78213b06bed08c8c6f26e5e8b" style="height: 2.843ex; vertical-align: -1.005ex; width: 14.285ex;" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>g</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>h</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>−</mo>
<mi>T</mi>
<mrow>
<mrow>
<mover>
<msub>
<mi>s</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {g_{i}}}={\bar {h_{i}}}-T{\bar {s_{i}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/dab09d195fa735746ca5b253f96b57be019508ca" style="height: 2.843ex; vertical-align: -0.671ex; width: 13.513ex;" /></span>
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>s</mi>
<mrow>
<mi>i</mi>
<mo>,</mo>
<mrow>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mi>R</mi>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta s_{i,\mathrm {mix} }=-R\sum _{i}\ln x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/44342012cc17272632c4b74b688d0183710cd7ad" style="height: 5.509ex; vertical-align: -3.005ex; width: 22.233ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>S</mi>
<mrow>
<mrow>
<mi mathvariant="normal">m</mi>
<mo>,</mo>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mi>R</mi>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta S_{\mathrm {m,mix} }=-R\sum _{i}x_{i}\ln x_{i}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b1ca674767d7b589bb7f71a9190694a4f6fded7b" style="height: 5.509ex; vertical-align: -3.005ex; width: 26.532ex;" /></span></dd></dl>
<h2><span class="mw-headline" id="Consequences">Consequences</span></h2><p>Solvent–solute
interactions are the same as solute–solute and solvent–solvent
interactions, on average. Consequently, the enthalpy of mixing
(solution) is zero and the change in <a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy">Gibbs free energy</a> on mixing is determined solely by the <a href="https://en.wikipedia.org/wiki/Entropy_of_mixing" title="Entropy of mixing">entropy of mixing</a>. Hence the molar Gibbs free energy of mixing is
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>G</mi>
<mrow>
<mrow>
<mi mathvariant="normal">m</mi>
<mo>,</mo>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G_{\mathrm {m,mix} }=RT\sum _{i}x_{i}\ln x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4c86e404b97bbfe49174715fda0389029e18bdd9" style="height: 5.509ex; vertical-align: -3.005ex; width: 26.116ex;" /></span></dd></dl>
<p>or for a two-component ideal solution
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>G</mi>
<mrow>
<mrow>
<mi mathvariant="normal">m</mi>
<mo>,</mo>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<mo stretchy="false">(</mo>
<msub>
<mi>x</mi>
<mrow>
<mi>A</mi>
</mrow>
</msub>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>A</mi>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>x</mi>
<mrow>
<mi>B</mi>
</mrow>
</msub>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>B</mi>
</mrow>
</msub>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G_{\mathrm {m,mix} }=RT(x_{A}\ln x_{A}+x_{B}\ln x_{B})}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/edee8390935eeabfd2aa0180e3497031c7a529ef" style="height: 3.009ex; vertical-align: -1.005ex; width: 36.298ex;" /></span></dd></dl>
<p>where m denotes molar, i.e., change in Gibbs free energy per mole of solution, and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e87000dd6142b81d041896a30fe58f0c3acb2158" style="height: 2.009ex; vertical-align: -0.671ex; width: 2.129ex;" /></span> is the mole fraction of component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span>. Note that this free energy of mixing is always negative (since each <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>∈</mo>
<mo stretchy="false">[</mo>
<mn>0</mn>
<mo>,</mo>
<mn>1</mn>
<mo stretchy="false">]</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}\in [0,1]}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a32830173af0dc0eaf16f580cc75ef2f78b4f15e" style="height: 2.843ex; vertical-align: -0.838ex; width: 9.623ex;" /></span>, each <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \ln x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0722112a359701cfbf69c0ad59042a6e99141696" style="height: 2.509ex; vertical-align: -0.671ex; width: 4.456ex;" /></span> or its limit for <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">→</mo>
<mn>0</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}\to 0}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/51dc460b0126d66704a838736d663b0fbbdee3f3" style="height: 2.509ex; vertical-align: -0.671ex; width: 6.906ex;" /></span> must be negative (infinite)), i.e., <i>ideal solutions are miscible at any composition</i> and no phase separation will occur.
</p><p>The equation above can be expressed in terms of <a href="https://en.wikipedia.org/wiki/Chemical_potential" title="Chemical potential">chemical potentials</a> of the individual components
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>G</mi>
<mrow>
<mrow>
<mi mathvariant="normal">m</mi>
<mo>,</mo>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<munder>
<mo>∑</mo>
<mrow>
<mi>i</mi>
</mrow>
</munder>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>μ</mi>
<mrow>
<mi>i</mi>
<mo>,</mo>
<mrow>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G_{\mathrm {m,mix} }=\sum _{i}x_{i}\Delta \mu _{i,\mathrm {mix} }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/483bedaba5097f1db113f3be4acfd63f56802cc1" style="height: 5.509ex; vertical-align: -3.005ex; width: 24.774ex;" /></span></dd></dl>
<p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>μ</mi>
<mrow>
<mi>i</mi>
<mo>,</mo>
<mrow>
<mi mathvariant="normal">m</mi>
<mi mathvariant="normal">i</mi>
<mi mathvariant="normal">x</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta \mu _{i,\mathrm {mix} }=RT\ln x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/90a94a110648e9b434e91b7625ad92a64d6ff263" style="height: 2.843ex; vertical-align: -1.005ex; width: 18.631ex;" /></span> is the change in chemical potential of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> on mixing. If the chemical potential of pure liquid <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> is denoted <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu _{i}^{*}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/506eeee39cf2a6a21e6f78251b5194fedde29d96" style="height: 2.843ex; vertical-align: -1.005ex; width: 2.456ex;" /></span>, then the chemical potential of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> in an ideal solution is
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<msubsup>
<mi>μ</mi>
<mrow>
<mi>i</mi>
</mrow>
<mrow>
<mo>∗</mo>
</mrow>
</msubsup>
<mo>+</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu _{i}=\mu _{i}^{*}+RT\ln x_{i}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6a11a7aa36b540327634c292784c995000186f66" style="height: 2.843ex; vertical-align: -1.005ex; width: 19.486ex;" /></span></dd></dl>
<p>Any component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> of an ideal solution obeys <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Raoult%27s_Law" title="Raoult's Law">Raoult's Law</a> over the entire composition range:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mtext> </mtext>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<mo stretchy="false">(</mo>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msub>
<mo stretchy="false">)</mo>
<mrow>
<mtext>pure</mtext>
</mrow>
</msub>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \ p_{i}=(p_{i})_{\text{pure}}x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1fffe3100f1f0160e1cd7de84af4a4ce7aae917c" style="height: 3.009ex; vertical-align: -1.005ex; width: 14.991ex;" /></span></dd></dl>
<p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<msub>
<mi>p</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msub>
<mo stretchy="false">)</mo>
<mrow>
<mtext>pure</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle (p_{i})_{\text{pure}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ad663f224fce65b89f6dd8db6f1e1be85a565146" style="height: 3.009ex; vertical-align: -1.005ex; width: 7.213ex;" /></span> is the equilibrium vapor pressure of pure component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7beb41cde977577a7aa598a9defd58dc8d529bb8" style="height: 2.009ex; vertical-align: -0.671ex; width: 2.516ex;" /></span>is the mole fraction of component <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>i</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle i}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" style="height: 2.176ex; vertical-align: -0.338ex; width: 0.802ex;" /></span> in solution.
</p>
<h2><span class="mw-headline" id="Non-ideality">Non-ideality</span></h2><p>Deviations from ideality can be described by the use of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Margules_function" title="Margules function">Margules functions</a> or <a href="https://en.wikipedia.org/wiki/Activity_coefficient" title="Activity coefficient">activity coefficients</a>.
A single Margules parameter may be sufficient to describe the
properties of the solution if the deviations from ideality are modest;
such solutions are termed <i><a href="https://en.wikipedia.org/wiki/Regular_solution" title="Regular solution">regular</a></i>.
</p><p>In contrast to ideal solutions, where volumes are strictly
additive and mixing is always complete, the volume of a non-ideal
solution is not, in general, the simple sum of the volumes of the
component pure liquids and <a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">solubility</a> is not guaranteed over the whole composition range. By measurement of densities, <a href="https://en.wikipedia.org/wiki/Thermodynamic_activity" title="Thermodynamic activity">thermodynamic activity</a> of components can be determined.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-78648573985911826202024-03-16T14:14:00.000-04:002024-03-16T14:14:52.290-04:00Solution (chemistry)<div class="vector-body-before-content"><div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
</div>
<div id="contentSub"><div id="mw-content-subtitle"></div></div>
<div class="hatnote navigation-not-searchable" role="note"><a href="https://en.wikipedia.org/wiki/Solution_(chemistry)">https://en.wikipedia.org/wiki/Solution_(chemistry)</a><br /></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:SaltInWaterSolutionLiquid.jpg"><img class="mw-file-element" data-file-height="1013" data-file-width="534" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/89/SaltInWaterSolutionLiquid.jpg/170px-SaltInWaterSolutionLiquid.jpg" width="211" /></a><figcaption>Making a <a href="https://en.wikipedia.org/wiki/Saline_water" title="Saline water">saline water</a> solution by dissolving <a href="https://en.wikipedia.org/wiki/Salt" title="Salt">table salt</a> (<a href="https://en.wikipedia.org/wiki/Sodium_chloride" title="Sodium chloride">NaCl</a>) in <a href="https://en.wikipedia.org/wiki/Water" title="Water">water</a>. The salt is the solute and the water the solvent.</figcaption></figure>
<p>In <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, a <b>solution</b> is a special type of <a href="https://en.wikipedia.org/wiki/Mixture#Homogeneous_and_heterogeneous_mixtures" title="Mixture">homogeneous mixture</a> composed of two or more substances. In such a <a href="https://en.wikipedia.org/wiki/Mixture" title="Mixture">mixture</a>, a <b>solute</b> is a substance <a href="https://en.wikipedia.org/wiki/Solvation" title="Solvation">dissolved</a> in another substance, known as a <a href="https://en.wikipedia.org/wiki/Solvent" title="Solvent">solvent</a>.
If the attractive forces between the solvent and solute particles are
greater than the attractive forces holding the solute particles
together, the solvent particles pull the solute particles apart and
surround them. These surrounded solute particles then move away from the
solid solute and out into the solution. The mixing process of a
solution happens at a scale where the effects of <a href="https://en.wikipedia.org/wiki/Chemical_polarity" title="Chemical polarity">chemical polarity</a> are involved, resulting in interactions that are specific to <a href="https://en.wikipedia.org/wiki/Solvation" title="Solvation">solvation</a>. The solution usually has the <a href="https://en.wikipedia.org/wiki/State_of_matter" title="State of matter">state</a>
of the solvent when the solvent is the larger fraction of the mixture,
as is commonly the case. One important parameter of a solution is the <a href="https://en.wikipedia.org/wiki/Concentration" title="Concentration">concentration</a>, which is a measure of the amount of solute in a given amount of solution or solvent. The term "<a href="https://en.wikipedia.org/wiki/Aqueous_solution" title="Aqueous solution">aqueous solution</a>" is used when one of the solvents is <a href="https://en.wikipedia.org/wiki/Water" title="Water">water</a>.
</p>
<h2><span class="mw-headline" id="Characteristics">Characteristics</span></h2>
<ul><li>A solution is a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Homogeneous_mixture" title="Homogeneous mixture">homogeneous mixture</a> of two or more substances.</li><li>The particles of solute in a solution cannot be seen by the naked eye. By contrast, particles may be visible in a <a href="https://en.wikipedia.org/wiki/Suspension_(chemistry)" title="Suspension (chemistry)">suspension</a>.</li><li>A solution does not cause beams of <a href="https://en.wikipedia.org/wiki/Light" title="Light">light</a> to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Light_scattering" title="Light scattering">scatter</a>. By contrast, the particles in a suspension or colloid can cause <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Tyndall_scattering" title="Tyndall scattering">Tyndall scattering</a> or <a href="https://en.wikipedia.org/wiki/Rayleigh_scattering" title="Rayleigh scattering">Rayleigh scattering</a>.</li><li>A solution is stable, and solutes will not precipitate unless added in excess of the mixture's <a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">solubility</a>,
at which point the excess would remain in its solid phase. A solution
containing more dissolved solutes than at equilibrium is referred to as <a href="https://en.wikipedia.org/wiki/Supersaturation" title="Supersaturation">supersaturated</a>.</li><li>The solutes and solvents in a solution cannot be separated by <a href="https://en.wikipedia.org/wiki/Filtration" title="Filtration">filtration</a> (or mechanically).</li><li>It is composed of only one <a href="https://en.wikipedia.org/wiki/Phase_(matter)" title="Phase (matter)">phase</a>.</li></ul>
<h2><span class="mw-headline" id="Types">Types</span></h2>
<p><i>Homogeneous</i> means that the components of the mixture form a single phase. <i>Heterogeneous</i>
means that the components of the mixture are of different phase. The
properties of the mixture (such as concentration, temperature, and
density) can be uniformly distributed through the volume but only in
absence of diffusion phenomena or after their completion. Usually, the
substance present in the greatest amount is considered the solvent.
Solvents can be gases, liquids, or solids. One or more components
present in the solution other than the solvent are called solutes. The
solution has the same <a href="https://en.wikipedia.org/wiki/State_of_matter" title="State of matter">physical state</a> as the solvent.
</p>
<h3><span class="mw-headline" id="Gaseous_mixtures">Gaseous mixtures</span></h3>
<p>If the solvent is a <a href="https://en.wikipedia.org/wiki/Gas" title="Gas">gas</a>,
only gases (non-condensable) or vapors (condensable) are dissolved
under a given set of conditions. An example of a gaseous solution is <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Air" title="Air">air</a>
(oxygen and other gases dissolved in nitrogen). Since interactions
between gaseous molecules play almost no role, non-condensable gases
form rather trivial solutions. In the literature, they are not even
classified as solutions, but simply addressed as homogeneous <a href="https://en.wikipedia.org/wiki/Mixture" title="Mixture">mixtures</a> of gases. The <a href="https://en.wikipedia.org/wiki/Brownian_motion" title="Brownian motion">Brownian motion</a>
and the permanent molecular agitation of gas molecules guarantee the
homogeneity of the gaseous systems. Non-condensable gases mixtures
(e.g., air/CO<sub>2</sub>, or air/xenon) do not spontaneously demix, nor
sediment, as distinctly stratified and separate gas layers as a
function of their <a href="https://en.wikipedia.org/wiki/Relative_density" title="Relative density">relative density</a>. <a href="https://en.wikipedia.org/wiki/Diffusion" title="Diffusion">Diffusion</a> forces efficiently counteract <a href="https://en.wikipedia.org/wiki/Gravity" title="Gravity">gravitation</a> forces under normal conditions prevailing on Earth. The case of condensable vapors is different: once the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Saturation_vapor_pressure" title="Saturation vapor pressure">saturation vapor pressure</a> at a given temperature is reached, vapor excess condenses into the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Liquid_state" title="Liquid state">liquid state</a>.
</p>
<h3><span class="mw-headline" id="Liquid_solutions">Liquid solutions</span></h3>
<p>If the solvent is a <a href="https://en.wikipedia.org/wiki/Liquid" title="Liquid">liquid</a>, then almost all gases, liquids, and solids can be dissolved. Here are some examples:
</p>
<ul><li>Gas in liquid:
<ul><li><a href="https://en.wikipedia.org/wiki/Oxygen" title="Oxygen">Oxygen</a> in water</li><li><a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide">Carbon dioxide</a>
in water – a less simple example, because the solution is accompanied
by a chemical reaction (formation of ions). The visible bubbles in <a href="https://en.wikipedia.org/wiki/Carbonated_water" title="Carbonated water">carbonated water</a> are not the dissolved gas, but only an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Effervescence_(chemistry)" title="Effervescence (chemistry)">effervescence</a>
of carbon dioxide that has come out of solution; the dissolved gas
itself is not visible since it is dissolved on a molecular level.</li></ul></li><li>Liquid in liquid:
<ul><li>The mixing of two or more substances of the same chemistry but
different concentrations to form a constant. (Homogenization of
solutions)</li><li>Alcoholic beverages are basically solutions of ethanol in water.</li></ul></li><li>Solid in liquid:
<ul><li><a href="https://en.wikipedia.org/wiki/Sucrose" title="Sucrose">Sucrose</a> (table <a href="https://en.wikipedia.org/wiki/Sugar" title="Sugar">sugar</a>) in water</li><li><a href="https://en.wikipedia.org/wiki/Sodium_chloride" title="Sodium chloride">Sodium chloride</a> (NaCl) (table <a href="https://en.wikipedia.org/wiki/Salt" title="Salt">salt</a>) or any other <a href="https://en.wikipedia.org/wiki/Salt_(chemistry)" title="Salt (chemistry)">salt</a> in water, which forms an <a href="https://en.wikipedia.org/wiki/Electrolyte" title="Electrolyte">electrolyte</a>: When dissolving, salt dissociates into <a href="https://en.wikipedia.org/wiki/Ion" title="Ion">ions</a>.</li></ul></li><li><a href="https://en.wikipedia.org/wiki/Aqueous_solution" title="Aqueous solution">Solutions in water</a> are especially common, and are called <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Aqueous_solutions" title="Aqueous solutions">aqueous solutions</a>.</li><li>Non-aqueous solutions are when the liquid solvent involved is not water.</li></ul>
<p>Counterexamples are provided by liquid mixtures that are not <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Homogeneous_and_heterogeneous_mixtures" title="Homogeneous and heterogeneous mixtures">homogeneous</a>: <a href="https://en.wikipedia.org/wiki/Colloid" title="Colloid">colloids</a>, <a href="https://en.wikipedia.org/wiki/Suspension_(chemistry)" title="Suspension (chemistry)">suspensions</a>, <a href="https://en.wikipedia.org/wiki/Emulsion" title="Emulsion">emulsions</a> are not considered solutions.
</p><p><a href="https://en.wikipedia.org/wiki/Body_fluid" title="Body fluid">Body fluids</a>
are examples of complex liquid solutions, containing many solutes. Many
of these are electrolytes since they contain solute ions, such as <a href="https://en.wikipedia.org/wiki/Potassium" title="Potassium">potassium</a>. Furthermore, they contain solute molecules like sugar and <a href="https://en.wikipedia.org/wiki/Urea" title="Urea">urea</a>. Oxygen and carbon dioxide are also essential components of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Blood_chemistry" title="Blood chemistry">blood chemistry</a>, where significant changes in their concentrations may be a sign of severe illness or injury.
</p>
<h3><span class="mw-headline" id="Solid_solutions">Solid solutions</span></h3>
<p>If the solvent is a <a href="https://en.wikipedia.org/wiki/Solid" title="Solid">solid</a>, then gases, liquids, and solids can be dissolved.
</p>
<ul><li>Gas in solids:
<ul><li><a href="https://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">Hydrogen</a> dissolves rather well in metals, especially in <a href="https://en.wikipedia.org/wiki/Palladium" title="Palladium">palladium</a>; this is studied as a means of <a href="https://en.wikipedia.org/wiki/Hydrogen_storage" title="Hydrogen storage">hydrogen storage</a>.</li></ul></li><li>Liquid in solid:
<ul><li><a href="https://en.wikipedia.org/wiki/Mercury_(element)" title="Mercury (element)">Mercury</a> in <a href="https://en.wikipedia.org/wiki/Gold" title="Gold">gold</a>, forming an <a href="https://en.wikipedia.org/wiki/Amalgam_(chemistry)" title="Amalgam (chemistry)">amalgam</a></li><li>Water in solid salt or <a href="https://en.wikipedia.org/wiki/Sugar" title="Sugar">sugar</a>, forming moist solids</li><li><a href="https://en.wikipedia.org/wiki/Hexane" title="Hexane">Hexane</a> in <a href="https://en.wikipedia.org/wiki/Paraffin_wax" title="Paraffin wax">paraffin wax</a></li><li><a href="https://en.wikipedia.org/wiki/Polymer" title="Polymer">Polymers</a> containing <a href="https://en.wikipedia.org/wiki/Plasticizer" title="Plasticizer">plasticizers</a> such as <a href="https://en.wikipedia.org/wiki/Bis(2-ethylhexyl)_phthalate" title="Bis(2-ethylhexyl) phthalate">phthalate</a> (liquid) in <a href="https://en.wikipedia.org/wiki/Polyvinyl_chloride" title="Polyvinyl chloride">PVC</a> (solid)</li></ul></li><li>Solid in solid:
<ul><li><a href="https://en.wikipedia.org/wiki/Steel" title="Steel">Steel</a>, basically a solution of carbon atoms in a crystalline matrix of iron atoms</li><li><a href="https://en.wikipedia.org/wiki/Alloy" title="Alloy">Alloys</a> like <a href="https://en.wikipedia.org/wiki/Bronze" title="Bronze">bronze</a> and many others</li><li><a href="https://en.wikipedia.org/wiki/Radium" title="Radium">Radium</a> <a href="https://en.wikipedia.org/wiki/Sulfate" title="Sulfate">sulfate</a> dissolved in <a href="https://en.wikipedia.org/wiki/Barium_sulfate" title="Barium sulfate">barium sulfate</a>: a true solid solution of Ra in BaSO<sub>4</sub></li></ul></li></ul>
<h2><span class="mw-headline" id="Solubility">Solubility</span></h2>
<div class="hatnote navigation-not-searchable" role="note">Main articles: <a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a> and <a href="https://en.wikipedia.org/wiki/Solvation" title="Solvation">Solvation</a></div>
<p>The ability of one <a href="https://en.wikipedia.org/wiki/Chemical_compound" title="Chemical compound">compound</a> to dissolve in another compound is called <a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">solubility</a>.<sup class="noprint Inline-Template" style="margin-left: 0.1em; white-space: nowrap;">[<i><a href="https://en.wikipedia.org/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="The text near this tag may need clarification or removal of jargon. (August 2021)">clarification needed</span></a></i>]</sup> When a liquid can completely dissolve in another liquid the two liquids are <i>miscible</i>. Two substances that can never mix to form a solution are said to be <i>immiscible</i>.
</p><p>All solutions have a positive <a href="https://en.wikipedia.org/wiki/Entropy" title="Entropy">entropy</a>
of mixing. The interactions between different molecules or ions may be
energetically favored or not. If interactions are unfavorable, then the <a href="https://en.wikipedia.org/wiki/Thermodynamic_free_energy" title="Thermodynamic free energy">free energy</a>
decreases with increasing solute concentration. At some point, the
energy loss outweighs the entropy gain, and no more solute particles can be dissolved; the solution is said to be <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Saturated_solution" title="Saturated solution">saturated</a>.
However, the point at which a solution can become saturated can change
significantly with different environmental factors, such as <a href="https://en.wikipedia.org/wiki/Temperature" title="Temperature">temperature</a>, <a href="https://en.wikipedia.org/wiki/Pressure" title="Pressure">pressure</a>, and contamination. For some solute-solvent combinations, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Supersaturated" title="Supersaturated">supersaturated</a>
solution can be prepared by raising the solubility (for example by
increasing the temperature) to dissolve more solute and then lowering it
(for example by cooling).
</p><p>Usually, the greater the temperature of the solvent, the more of a
given solid solute it can dissolve. However, most gases and some
compounds exhibit solubilities that decrease with increased temperature.
Such behavior is a result of an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Exothermic" title="Exothermic">exothermic</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Enthalpy_of_solution" title="Enthalpy of solution">enthalpy of solution</a>. Some <a href="https://en.wikipedia.org/wiki/Surfactant" title="Surfactant">surfactants</a>
exhibit this behaviour. The solubility of liquids in liquids is
generally less temperature-sensitive than that of solids or gases.
</p>
<h2><span class="mw-headline" id="Properties">Properties</span></h2>
<p>The physical properties of compounds such as <a href="https://en.wikipedia.org/wiki/Melting_point" title="Melting point">melting point</a> and <a href="https://en.wikipedia.org/wiki/Boiling_point" title="Boiling point">boiling point</a> change when other compounds are added. Together they are called <a href="https://en.wikipedia.org/wiki/Colligative_properties" title="Colligative properties">colligative properties</a>. There are several ways to quantify the amount of one compound dissolved in the other compounds collectively called <a href="https://en.wikipedia.org/wiki/Concentration" title="Concentration">concentration</a>. Examples include <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Molarity" title="Molarity">molarity</a>, <a href="https://en.wikipedia.org/wiki/Volume_fraction" title="Volume fraction">volume fraction</a>, and <a href="https://en.wikipedia.org/wiki/Mole_fraction" title="Mole fraction">mole fraction</a>.
</p><p>The properties of <a href="https://en.wikipedia.org/wiki/Ideal_solution" title="Ideal solution">ideal solutions</a> can be calculated by the <a href="https://en.wikipedia.org/wiki/Linear_combination" title="Linear combination">linear combination</a> of the properties of its components. If both solute and solvent exist in equal quantities (such as in a 50% <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">ethanol</a>,
50% water solution), the concepts of "solute" and "solvent" become less
relevant, but the substance that is more often used as a solvent is
normally designated as the solvent (in this example, water).
</p>
<h2><span class="mw-headline" id="Liquid_solution_characteristics">Liquid solution characteristics</span></h2>
<div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Solvent#Solvent_classifications" title="Solvent">Solvent § Solvent classifications</a></div>
<p>In principle, all types of liquids can behave as solvents: liquid <a href="https://en.wikipedia.org/wiki/Noble_gas" title="Noble gas">noble gases</a>,
molten metals, molten salts, molten covalent networks, and molecular
liquids. In the practice of chemistry and biochemistry, most solvents
are molecular liquids. They can be classified into <a href="https://en.wikipedia.org/wiki/Chemical_polarity" title="Chemical polarity">polar and non-polar</a>, according to whether their molecules possess a permanent <a href="https://en.wikipedia.org/wiki/Electric_dipole_moment" title="Electric dipole moment">electric dipole moment</a>. Another distinction is whether their molecules can form <a href="https://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond">hydrogen bonds</a> (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Protic" title="Protic">protic</a> and aprotic solvents). <a href="https://en.wikipedia.org/wiki/Water" title="Water">Water</a>, the most commonly used solvent, is both polar and sustains hydrogen bonds.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg"><img class="mw-file-element" data-file-height="397" data-file-width="400" height="397" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/3D_model_hydrogen_bonds_in_water.svg/150px-3D_model_hydrogen_bonds_in_water.svg.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Water" title="Water">Water</a> is a good solvent because the molecules are polar and capable of forming hydrogen bonds (1).</figcaption></figure>
<p>Salts dissolve in polar solvents, forming positive and negative ions
that are attracted to the negative and positive ends of the solvent
molecule, respectively. If the solvent is water, <a href="https://en.wikipedia.org/wiki/Solvation" title="Solvation">hydration</a>
occurs when the charged solute ions become surrounded by water
molecules. A standard example is aqueous saltwater. Such solutions are
called <a href="https://en.wikipedia.org/wiki/Electrolyte" title="Electrolyte">electrolytes</a>. Whenever salt dissolves in water <a href="https://en.wikipedia.org/wiki/Ion_association" title="Ion association">ion association</a> has to be taken into account.
</p><p>Polar solutes dissolve in polar solvents, forming polar bonds or hydrogen bonds. As an example, all alcoholic beverages are <a href="https://en.wikipedia.org/wiki/Aqueous_solution" title="Aqueous solution">aqueous solutions</a> of <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">ethanol</a>. On the other hand, non-polar solutes dissolve better in non-polar solvents. Examples are hydrocarbons such as <a href="https://en.wikipedia.org/wiki/Oil" title="Oil">oil</a> and <a href="https://en.wikipedia.org/wiki/Petroleum" title="Petroleum">grease</a> that easily mix, while being incompatible with water.
</p><p>An example of the immiscibility of oil and water is a leak of
petroleum from a damaged tanker, that does not dissolve in the ocean
water but rather floats on the surface.
</p>
<h3><span class="mw-headline" id="Preparation_from_constituent_ingredients">Preparation from constituent ingredients</span></h3>
<p>It is common practice in laboratories to make a solution directly
from its constituent ingredients. There are three cases in practical
calculation:
</p>
<ul><li>Case 1: amount of solvent volume is given.</li><li>Case 2: amount of solute mass is given.</li><li>Case 3: amount of final solution volume is given.</li></ul>
<p>In the following equations, A is solvent, B is solute, and C is
concentration. Solute volume contribution is considered through the
ideal solution model.
</p>
<ul><li>Case 1: amount (mL) of solvent volume V<sub>A</sub> is given. Solute mass m<sub>B</sub> = C V<sub>A</sub> d<sub>A</sub> /(100-C/d<sub>B</sub>)</li><li>Case 2: amount of solute mass m<sub>B</sub> is given. Solvent volume V<sub>A</sub> = m<sub>B</sub> (100/C-1/ d<sub>B</sub> )</li><li>Case 3: amount (mL) of final solution volume Vt is given. Solute mass m<sub>B</sub> = C Vt /100; Solvent volume V<sub>A</sub>=(100/C-1/ d<sub>B</sub>) m<sub>B</sub></li><li>Case 2: solute mass is known, V<sub>A</sub> = m<sub>B</sub> 100/C</li><li>Case 3: total solution volume is known, same equation as case 1. V<sub>A</sub>=Vt; m<sub>B</sub> = C V<sub>A</sub> /100</li></ul>
<p>Example: Make 2 g/100mL of NaCl solution with 1 L <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Water_(properties)" title="Water (properties)">water</a>.
The density of the resulting solution is considered to be equal to that
of water, statement holding especially for dilute solutions, so the
density information is not required.
</p>
<dl><dd>m<sub>B</sub> = C V<sub>A</sub> = ( 2 / 100 ) g/mL × 1000 mL = 20 g</dd></dl>
<p>Chemists often make concentrated <b>stock solutions</b> that may then be diluted as needed for laboratory applications. <a href="https://en.wikipedia.org/wiki/Standard_solution" title="Standard solution">Standard solutions</a> are those where concentrations of solutes are accurately and precisely known.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-53393748953712524162024-03-16T13:32:00.003-04:002024-03-16T13:32:28.195-04:00Apparent molar property<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div><div class="noprint" id="siteSub"><a href="https://en.wikipedia.org/wiki/Apparent_molar_property">https://en.wikipedia.org/wiki/Apparent_molar_property</a> </div>
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<p>In <a href="https://en.wikipedia.org/wiki/Thermodynamics" title="Thermodynamics">thermodynamics</a>, an <b>apparent molar property</b> of a <a href="https://en.wikipedia.org/wiki/Solution_(chemistry)" title="Solution (chemistry)">solution</a> component in a <a href="https://en.wikipedia.org/wiki/Mixture" title="Mixture">mixture</a> or solution is a quantity defined with the purpose of isolating the contribution of each component to the <a href="https://en.wikipedia.org/wiki/Ideal_solution" title="Ideal solution">non-ideality of the mixture</a>. It shows the change in the corresponding solution property (for example, <a href="https://en.wikipedia.org/wiki/Volume" title="Volume">volume</a>) per <a href="https://en.wikipedia.org/wiki/Mole_(unit)" title="Mole (unit)">mole</a> of that component added, when all of that component is added to the solution. It is described as <i>apparent</i> because it appears to represent the molar property of that component <i>in solution</i>,
provided that the properties of the other solution components are
assumed to remain constant during the addition. However this assumption
is often not justified, since the values of apparent molar properties of
a component may be quite different from its molar properties in the
pure state.
</p><p>For instance, the volume of a solution containing two components identified as <a href="https://en.wikipedia.org/wiki/Solvent" title="Solvent">solvent</a> and solute is given by
</p>
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<p>where <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
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is the number of moles of the solute in the solution. By dividing this
relation to the molar amount of one component a relation between the
apparent molar property of a component and the mixing ratio of
components can be obtained.
</p><p>This equation serves as the definition of <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3aa761607b6e4ba23d3f9bc9d32dcb4166409982" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.44ex;" /></span></span>.
The first term is equal to the volume of the same quantity of solvent
with no solute, and the second term is the change of volume on addition
of the solute. <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3aa761607b6e4ba23d3f9bc9d32dcb4166409982" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.44ex;" /></span></span> may then be considered as the molar volume of the solute <i>if it is assumed</i>
that the molar volume of the solvent is unchanged by the addition of
solute. However this assumption must often be considered unrealistic as
shown in the examples below, so that
<span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3aa761607b6e4ba23d3f9bc9d32dcb4166409982" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.44ex;" /></span></span> is described only as an <i>apparent</i> value.
</p><p>An apparent molar quantity can be similarly defined for the component identified as solvent <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{0}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9a227f279afbd368411e0d68cf58ee1f42d4e96e" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.44ex;" /></span></span>. Some authors have reported apparent molar volumes of both (liquid) components of the same solution. This procedure can be extended to ternary and multicomponent mixtures.
</p><p>Apparent quantities can also be expressed using mass instead of
number of moles. This expression produces apparent specific quantities,
like the apparent specific volume.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mi>V</mi>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mtext> </mtext>
<mo>=</mo>
<msub>
<mi>v</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mi>v</mi>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>m</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V=V_{0}+{}^{\phi }{V}_{1}\ =v_{0}m_{0}+{}^{\phi }{v}_{1}m_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/89c035735b62821077e546e96d7a803701d2f96d" style="height: 3.009ex; vertical-align: -0.671ex; width: 32.428ex;" /></span></dd></dl>
<p>where the specific quantities are denoted with small letters.
</p><p>Apparent (molar) properties are not constants (even at a given temperature), but are functions of the composition. At infinite <a class="extiw" href="https://en.wiktionary.org/wiki/dilution" title="wikt:dilution">dilution</a>, an apparent molar property and the corresponding <a href="https://en.wikipedia.org/wiki/Partial_molar_property" title="Partial molar property">partial molar property</a> become equal.
</p><p>Some apparent molar properties that are commonly used are apparent molar <a href="https://en.wikipedia.org/wiki/Enthalpy" title="Enthalpy">enthalpy</a>, apparent molar <a href="https://en.wikipedia.org/wiki/Heat_capacity" title="Heat capacity">heat capacity</a>, and apparent molar volume.
</p>
<h2><span class="mw-headline" id="Relation_to_molality">Relation to molality</span></h2></div></div></div><p>The apparent (molal) volume of a solute can be expressed as a function of the <a href="https://en.wikipedia.org/wiki/Molality" title="Molality">molality</a> <i>b</i> of that solute (and of the densities of the solution and solvent). The volume of solution per mole of solute is
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<mn>1</mn>
<mi>ρ</mi>
</mfrac>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<mn>1</mn>
<mi>b</mi>
</mfrac>
</mrow>
<mo>+</mo>
<msub>
<mi>M</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
<mo>)</mo>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {1}{\rho }}\left({\frac {1}{b}}+M_{1}\right).}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b39862c4d6d412cdbf8e87603aec6c46b9e56252" style="height: 6.176ex; vertical-align: -2.505ex; width: 15.028ex;" /></span></dd></dl>
<p>Subtracting the volume of pure solvent per mole of solute gives the apparent molal volume:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<mi>m</mi>
<mi>ρ</mi>
</mfrac>
</mrow>
<mo>−</mo>
<mrow>
<mfrac>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msubsup>
<mi>ρ</mi>
<mrow>
<mn>0</mn>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msubsup>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<mrow>
<msub>
<mi>m</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
<mi>ρ</mi>
</mfrac>
</mrow>
<mo>−</mo>
<mrow>
<mfrac>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msubsup>
<mi>ρ</mi>
<mrow>
<mn>0</mn>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msubsup>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mi>ρ</mi>
</mfrac>
</mrow>
<mo>−</mo>
<mrow>
<mfrac>
<msub>
<mi>m</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msubsup>
<mi>ρ</mi>
<mrow>
<mn>0</mn>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msubsup>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>+</mo>
<mrow>
<mfrac>
<msub>
<mi>m</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mrow>
<mi>ρ</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}={\frac {V-V_{0}}{n_{1}}}=\left({\frac {m}{\rho }}-{\frac {m_{0}}{\rho _{0}^{0}}}\right){\frac {1}{n_{1}}}=\left({\frac {m_{1}+m_{0}}{\rho }}-{\frac {m_{0}}{\rho _{0}^{0}}}\right){\frac {1}{n_{1}}}=\left({\frac {m_{0}}{\rho }}-{\frac {m_{0}}{\rho _{0}^{0}}}\right){\frac {1}{n_{1}}}+{\frac {m_{1}}{\rho n_{1}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/aa6f755d8202dddeb0bae70e81fa0995a0590712" style="height: 7.509ex; vertical-align: -3.171ex; width: 90.695ex;" /></span></dd></dl>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mn>1</mn>
<mi>b</mi>
</mfrac>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<mn>1</mn>
<mi>ρ</mi>
</mfrac>
</mrow>
<mo>−</mo>
<mrow>
<mfrac>
<mn>1</mn>
<msubsup>
<mi>ρ</mi>
<mrow>
<mn>0</mn>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msubsup>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mo>+</mo>
<mrow>
<mfrac>
<msub>
<mi>M</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mi>ρ</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}={\frac {1}{b}}\left({\frac {1}{\rho }}-{\frac {1}{\rho _{0}^{0}}}\right)+{\frac {M_{1}}{\rho }}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7d808f6d14d799e9b1bc04e827d4412f6561f1ad" style="height: 7.509ex; vertical-align: -3.171ex; width: 28.174ex;" /></span></dd></dl>
<p>For more solutes the above equality is modified with the mean molar
mass of the solutes as if they were a single solute with molality b<sub>T</sub>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>12..</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>b</mi>
<mrow>
<mi>T</mi>
</mrow>
</msub>
</mfrac>
</mrow>
<mrow>
<mo>(</mo>
<mrow>
<mrow>
<mfrac>
<mn>1</mn>
<mi>ρ</mi>
</mfrac>
</mrow>
<mo>−</mo>
<mrow>
<mfrac>
<mn>1</mn>
<msubsup>
<mi>ρ</mi>
<mrow>
<mn>0</mn>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msubsup>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
<mo>+</mo>
<mrow>
<mfrac>
<mi>M</mi>
<mi>ρ</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{12..}={\frac {1}{b_{T}}}\left({\frac {1}{\rho }}-{\frac {1}{\rho _{0}^{0}}}\right)+{\frac {M}{\rho }}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ddf19e265919675722b186398cb876687bae6d50" style="height: 7.509ex; vertical-align: -3.171ex; width: 30.269ex;" /></span>, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>M</mi>
<mo>=</mo>
<mo>∑</mo>
<msub>
<mi>y</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msub>
<mi>M</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle M=\sum y_{i}M_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/12b31c25318712421c20c0da73c9b659940e332c" style="height: 3.843ex; vertical-align: -1.338ex; width: 14.275ex;" /></span></dd></dl>
<p>The sum of products molalities – apparent molar volumes of solutes in
their binary solutions equals the product between the sum of molalities
of solutes and apparent molar volume in ternary of multicomponent
solution mentioned above.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>123..</mn>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>+</mo>
<mo>.</mo>
<mo>.</mo>
<mo>.</mo>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>+</mo>
<mo>.</mo>
<mo>.</mo>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{123..}(b_{1}+b_{2}+b_{3}+...)=b_{1}{}^{\phi }{\tilde {V}}_{1}+b_{2}{}^{\phi }{\tilde {V}}_{2}+b_{3}{}^{\phi }{\tilde {V}}_{3}+...}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8db1627a78db95c24d828d2d36c4356bc950021b" style="height: 3.176ex; vertical-align: -0.838ex; width: 56.785ex;" /></span>,</dd></dl>
<h2><span class="mw-headline" id="Relation_to_mixing_ratio">Relation to mixing ratio</span></h2><p>A
relation between the apparent molar of a component of a mixture and
molar mixing ratio can be obtained by dividing the definition relation
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mi>V</mi>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mtext> </mtext>
<mo>=</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V=V_{0}+{}^{\phi }{V}_{1}\ ={\tilde {V}}_{0}n_{0}+{}^{\phi }{\tilde {V}}_{1}n_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/59dfcf00ff18b543f763e353b2722fb36326f03d" style="height: 3.009ex; vertical-align: -0.671ex; width: 32.456ex;" /></span></dd></dl>
<p>to the number of moles of one component. This gives the following relation:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mi>V</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>−</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mrow>
<mfrac>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<mi>V</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>−</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>r</mi>
<mrow>
<mn>01</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}={\frac {V}{n_{1}}}-{\tilde {V}}_{0}{\frac {n_{0}}{n_{1}}}={\frac {V}{n_{1}}}-{\tilde {V}}_{0}r_{01}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/84a803d13e366f8bddf9cf0c90aba8ba4a5d00d8" style="height: 5.509ex; vertical-align: -2.171ex; width: 34.394ex;" /></span></dd></dl>
<h2><span id="Relation_to_partial_.28molar.29_quantities"></span><span class="mw-headline" id="Relation_to_partial_(molar)_quantities">Relation to partial (molar) quantities</span></h2><p>Note
the contrasting definitions between partial molar quantity and apparent
molar quantity: in the case of partial molar volumes <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>,</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {V_{0}}},{\bar {V_{1}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/01584d35caf3531ea95bf72b93e09081217ee18d" style="height: 2.843ex; vertical-align: -0.671ex; width: 5.853ex;" /></span>, defined by partial derivatives
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">(</mo>
</mrow>
</mrow>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>V</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<msub>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">)</mo>
</mrow>
</mrow>
<mrow>
<mi>T</mi>
<mo>,</mo>
<mi>p</mi>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
</msub>
<mo>,</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">(</mo>
</mrow>
</mrow>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>V</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<msub>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">)</mo>
</mrow>
</mrow>
<mrow>
<mi>T</mi>
<mo>,</mo>
<mi>p</mi>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {V_{0}}}={\Big (}{\frac {\partial V}{\partial n_{0}}}{\Big )}_{T,p,n_{1}},{\bar {V_{1}}}={\Big (}{\frac {\partial V}{\partial n_{1}}}{\Big )}_{T,p,n_{0}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d9287becfff2e32794e0a9eff2f1ec5bd15482ac" style="height: 5.843ex; vertical-align: -2.338ex; width: 36.705ex;" /></span>,</dd></dl>
<p>one can write <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>d</mi>
<mi>V</mi>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mi>d</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mi>d</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle dV={\bar {V_{0}}}dn_{0}+{\bar {V_{1}}}dn_{1}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d1dd130ab67dc855720237bd0d7cbd635ef4fc5a" style="height: 2.843ex; vertical-align: -0.671ex; width: 21.091ex;" /></span>, and so <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V={\bar {V_{0}}}n_{0}+{\bar {V_{1}}}n_{1}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eb3d470ad5e637bfc7f92df3b7424f0c829948ed" style="height: 2.843ex; vertical-align: -0.671ex; width: 17.443ex;" /></span> always holds. In contrast, in the definition of apparent molar volume, the molar volume of the pure solvent, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\tilde {V}}_{0}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7fa8b67ad56b38f7c37b4f0a9ee5eb36dc3f5c5f" style="height: 3.009ex; vertical-align: -0.671ex; width: 2.841ex;" /></span>, is used instead, which can be written as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">(</mo>
</mrow>
</mrow>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>V</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<msub>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">)</mo>
</mrow>
</mrow>
<mrow>
<mi>T</mi>
<mo>,</mo>
<mi>p</mi>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mn>0</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\tilde {V_{0}}}={\Big (}{\frac {\partial V}{\partial n_{0}}}{\Big )}_{T,p,n_{1}=0}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f2d045e82041091c7baf71a4d080f31770ad12f2" style="height: 5.843ex; vertical-align: -2.338ex; width: 19.936ex;" /></span>,</dd></dl>
<p>for comparison. In other words, we assume that the volume of the
solvent does not change, and we use the partial molar volume where the
number of moles of the solute is exactly zero ("the molar volume").
Thus, in the defining expression for apparent molar volume <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/73aab7e3992e3dff12f7364aeecdaba0d7fdc575" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.053ex;" /></span>,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
<mo>=</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mi>V</mi>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mtext> </mtext>
<mo>=</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V=V_{0}+{}^{\phi }{V}_{1}\ ={\tilde {V}}_{0}n_{0}+{}^{\phi }{\tilde {V}}_{1}n_{1}\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/59dfcf00ff18b543f763e353b2722fb36326f03d" style="height: 3.009ex; vertical-align: -0.671ex; width: 32.456ex;" /></span>,</dd></dl>
<p>the term <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V_{0}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7ae15ff9b845587dc4e1816f59c3fed0e71a132f" style="height: 2.509ex; vertical-align: -0.671ex; width: 2.409ex;" /></span> is attributed to the pure solvent, while the "leftover" excess volume, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }V_{1}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/20d70c6e7259d4b20772ff326c4ae72ed80d3ad0" style="height: 3.009ex; vertical-align: -0.671ex; width: 3.621ex;" /></span>, is considered to originate from the solute. At high dilution with <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>≫</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>≈</mo>
<mn>0</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle n_{0}\gg n_{1}\approx 0}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7ecd08ef16d8acfa69dd1f626d4b997cfc72b5c9" style="height: 2.509ex; vertical-align: -0.671ex; width: 12.773ex;" /></span>, we have <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mo>≈</mo>
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\tilde {V_{0}}}\approx {\bar {V_{0}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/278e6636405d0c81f9890405aa3c6dfbfe8ba789" style="height: 3.009ex; vertical-align: -0.671ex; width: 7.917ex;" /></span>, and so the apparent molar volume and partial molar volume of the solute also converge: <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>≈</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}\approx {\bar {V}}_{1}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3e1ed25a5980fccfccc0c64d8031eb0771b1f726" style="height: 3.009ex; vertical-align: -0.671ex; width: 9.993ex;" /></span>.
</p><p>Quantitatively, the relation between partial molar properties and
the apparent ones can be derived from the definition of the apparent
quantities and of the molality. For volume,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<mi>b</mi>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>b</mi>
</mrow>
</mfrac>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {V_{1}}}={}^{\phi }{\tilde {V}}_{1}+b{\frac {\partial {}^{\phi }{\tilde {V}}_{1}}{\partial b}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b2a8095e502da895b8a719298b13e23adea1c889" style="height: 5.843ex; vertical-align: -2.005ex; width: 20.254ex;" /></span></dd></dl>
<h2><span class="mw-headline" id="Relation_to_the_activity_coefficient_of_an_electrolyte_and_its_solvation_shell_number">Relation to the activity coefficient of an electrolyte and its solvation shell number</span></h2><p>The ratio <i>r</i><sub>a</sub>
between the apparent molar volume of a dissolved electrolyte in a
concentrated solution and the molar volume of the solvent (water) can be
linked to the statistical component of the <a href="https://en.wikipedia.org/wiki/Activity_coefficient" title="Activity coefficient">activity coefficient</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>γ</mi>
<mrow>
<mi>s</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \gamma _{s}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/84dbd855432b9a80b1d2a4432070da6e8e281fa4" style="height: 2.176ex; vertical-align: -0.838ex; width: 2.208ex;" /></span> of the electrolyte and its <a href="https://en.wikipedia.org/wiki/Solvation_shell" title="Solvation shell">solvation shell</a> number <i>h</i>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>ln</mi>
<mo></mo>
<msub>
<mi>γ</mi>
<mrow>
<mi>s</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>h</mi>
<mo>−</mo>
<mi>ν</mi>
</mrow>
<mi>ν</mi>
</mfrac>
</mrow>
<mi>ln</mi>
<mo></mo>
<mo stretchy="false">(</mo>
<mn>1</mn>
<mo>+</mo>
<mrow>
<mfrac>
<mrow>
<mi>b</mi>
<msub>
<mi>r</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
</mrow>
<mn>55.5</mn>
</mfrac>
</mrow>
<mo stretchy="false">)</mo>
<mo>−</mo>
<mrow>
<mfrac>
<mi>h</mi>
<mi>ν</mi>
</mfrac>
</mrow>
<mi>ln</mi>
<mo></mo>
<mo stretchy="false">(</mo>
<mn>1</mn>
<mo>−</mo>
<mrow>
<mfrac>
<mrow>
<mi>b</mi>
<msub>
<mi>r</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
</mrow>
<mn>55.5</mn>
</mfrac>
</mrow>
<mo stretchy="false">)</mo>
<mo>+</mo>
<mrow>
<mfrac>
<mrow>
<mi>b</mi>
<msub>
<mi>r</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<msub>
<mi>r</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo>+</mo>
<mi>h</mi>
<mo>−</mo>
<mi>ν</mi>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>55.5</mn>
<mo stretchy="false">(</mo>
<mn>1</mn>
<mo>+</mo>
<mrow>
<mfrac>
<mrow>
<mi>b</mi>
<msub>
<mi>r</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
</mrow>
<mn>55.5</mn>
</mfrac>
</mrow>
<mo stretchy="false">)</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \ln \gamma _{s}={\frac {h-\nu }{\nu }}\ln(1+{\frac {br_{a}}{55.5}})-{\frac {h}{\nu }}\ln(1-{\frac {br_{a}}{55.5}})+{\frac {br_{a}(r_{a}+h-\nu )}{55.5(1+{\frac {br_{a}}{55.5}})}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/00028907a0e44c602c958cae2425c5f2336ea88e" style="height: 7.509ex; vertical-align: -3.671ex; width: 64.15ex;" /></span>,</dd></dl>
<p>where ν is the number of ions due to dissociation of the electrolyte, and b is the <a href="https://en.wikipedia.org/wiki/Molality" title="Molality">molality</a> as above.
</p>
<h2><span class="mw-headline" id="Examples">Examples</span></h2><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Principle_of_sigma-subadditivity.svg"><img class="mw-file-element" data-file-height="290" data-file-width="600" height="106" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/05/Principle_of_sigma-subadditivity.svg/220px-Principle_of_sigma-subadditivity.svg.png" width="220" /></a><figcaption>Everyday example: when sand is mixed with water, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bulk_volume" title="Bulk volume">bulk volume</a>
of the mixture is smaller than the sum of the individual volumes, as
the water can lodge in the spaces between the sand grains. A similar
situation with a different mechanism occurs when ethanol is mixed with
water.</figcaption></figure>
<h3><span class="mw-headline" id="Electrolytes">Electrolytes</span></h3><p>The apparent molar volume of salt is usually less than the molar volume of the solid salt. For instance, solid <a class="mw-redirect" href="https://en.wikipedia.org/wiki/NaCl" title="NaCl">NaCl</a> has a volume of 27 cm<sup>3</sup> per mole, but the apparent molar volume at low concentrations is only 16.6 cc/mole. In fact, some aqueous <a href="https://en.wikipedia.org/wiki/Electrolyte" title="Electrolyte">electrolytes</a> have negative apparent molar volumes: <a class="mw-redirect" href="https://en.wikipedia.org/wiki/NaOH" title="NaOH">NaOH</a> −6.7, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/LiOH" title="LiOH">LiOH</a> −6.0, and <a href="https://en.wikipedia.org/wiki/Sodium_carbonate" title="Sodium carbonate">Na<sub>2</sub>CO<sub>3</sub></a> −6.7 cm<sup>3</sup>/mole.
This means that their solutions in a given amount of water have a
smaller volume than the same amount of pure water. (The effect is small,
however.) The physical reason is that nearby water molecules are
strongly attracted to the ions so that they occupy less space.
</p>
<h3><span class="mw-headline" id="Alcohol">Alcohol</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Excess_Volume_Mixture_of_Ethanol_and_Water.png"><img class="mw-file-element" data-file-height="386" data-file-width="443" height="349" src="https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Excess_Volume_Mixture_of_Ethanol_and_Water.png/290px-Excess_Volume_Mixture_of_Ethanol_and_Water.png" width="400" /></a><figcaption>Excess volume of a mixture of ethanol and water</figcaption></figure>
<p>Another example of the apparent molar volume of the second component
is less than its molar volume as a pure substance is the case of <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">ethanol</a> in water. For example, at 20 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mass_percent" title="Mass percent">mass percents</a> ethanol, <a href="https://en.wikipedia.org/wiki/Ethanol_(data_page)#Properties_of_aqueous_ethanol_solutions" title="Ethanol (data page)">the solution has a volume</a> of 1.0326 liters per kg at 20 °C, while pure water is 1.0018 L/kg (1.0018 cc/g).
The apparent volume of the added ethanol is 1.0326 L – 0.8 kg x 1.0018
L/kg = 0.2317 L. The number of moles of ethanol is 0.2 kg /
(0.04607 kg/mol) = 4.341 mol, so that the apparent molar volume is
0.2317 L / 4.341 mol = 0.0532 L / mol = 53.2 cc/mole (1.16 cc/g).
However pure ethanol has a molar volume at this temperature of 58.4
cc/mole (1.27 cc/g).
</p><p>If the solution were <a href="https://en.wikipedia.org/wiki/Ideal_solution#Volume" title="Ideal solution">ideal</a>,
its volume would be the sum of the unmixed components. The volume of
0.2 kg pure ethanol is 0.2 kg x 1.27 L/kg = 0.254 L, and the volume of
0.8 kg pure water is 0.8 kg x 1.0018 L/kg = 0.80144 L, so the ideal
solution volume would be 0.254 L + 0.80144 L = 1.055 L. The nonideality
of the solution is reflected by a slight decrease (roughly 2.2%, 1.0326
rather than 1.055 L/kg) in the volume of the combined system upon
mixing. As the percent ethanol goes up toward 100%, the apparent molar
volume rises to the molar volume of pure ethanol.
</p>
<h3><span id="Electrolyte_.E2.80.93_non-electrolyte_systems"></span><span class="mw-headline" id="Electrolyte_–_non-electrolyte_systems">Electrolyte – non-electrolyte systems</span></h3><p>Apparent quantities can underline interactions in electrolyte – non-electrolyte systems which show interactions like <a href="https://en.wikipedia.org/wiki/Salting_in" title="Salting in">salting in</a> and <a href="https://en.wikipedia.org/wiki/Salting_out" title="Salting out">salting out</a>, but also give insights in ion-ion interactions, especially by their dependence on temperature.
</p>
<h2><span class="mw-headline" id="Multicomponent_mixtures_or_solutions">Multicomponent mixtures or solutions</span></h2><p>For multicomponent solutions, apparent molar properties can be defined in several ways. For the volume of a <i>ternary</i> (3-component) solution with one solvent and two solutes as an example, there would still be only one equation <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<mi>V</mi>
<mo>=</mo>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle (V={\tilde {V}}_{0}n_{0}+{}^{\phi }{\tilde {V}}_{1}n_{1}+{}^{\phi }{\tilde {V}}_{2}n_{2})}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/49ea992a8731464ad50d6125985a0649af63bec0" style="height: 3.176ex; vertical-align: -0.838ex; width: 30.671ex;" /></span>, which is insufficient to determine the two apparent volumes. (This is in contrast to <a href="https://en.wikipedia.org/wiki/Partial_molar_property" title="Partial molar property">partial molar properties</a>, which are well-defined <a href="https://en.wikipedia.org/wiki/Intensive_and_extensive_properties" title="Intensive and extensive properties">intensive properties</a>
of the materials and therefore unambiguously defined in multicomponent
systems. For example, partial molar volume is defined for each
component <i>i</i> as <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mover>
<msub>
<mi>V</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">¯</mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mo stretchy="false">(</mo>
<mi mathvariant="normal">∂</mi>
<mi>V</mi>
<mrow>
<mo>/</mo>
</mrow>
<mi mathvariant="normal">∂</mi>
<msub>
<mi>n</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<msub>
<mo stretchy="false">)</mo>
<mrow>
<mi>T</mi>
<mo>,</mo>
<mi>p</mi>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mi>j</mi>
<mo>≠</mo>
<mi>i</mi>
</mrow>
</msub>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\bar {V_{i}}}=(\partial V/\partial n_{i})_{T,p,n_{j\neq i}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eb18e250fa50268fef9601aa58772daff67c730d" style="height: 3.509ex; vertical-align: -1.338ex; width: 21.173ex;" /></span>.)
</p><p>One description of ternary aqueous solutions considers only the weighted mean apparent molar volume of the solutes, defined as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mo stretchy="false">(</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>12</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
<mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}(n_{1},n_{2})={}^{\phi }{\tilde {V}}_{12}={\frac {V-V_{0}}{n_{1}+n_{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/06a42b1912ae50061e1189124707f2284944d576" style="height: 5.676ex; vertical-align: -2.171ex; width: 30.387ex;" /></span>,</dd></dl>
<p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af0f6064540e84211d0ffe4dac72098adfa52845" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.787ex;" /></span> is the solution volume and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle V_{0}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7ae15ff9b845587dc4e1816f59c3fed0e71a132f" style="height: 2.509ex; vertical-align: -0.671ex; width: 2.409ex;" /></span> the volume of pure water.
This method can be extended for mixtures with more than 3 components.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mo stretchy="false">(</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>,</mo>
<mo>.</mo>
<mo>.</mo>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>123..</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mrow>
<mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>n</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>+</mo>
<mo>.</mo>
<mo>.</mo>
<mo>.</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}(n_{1},n_{2},n_{3},..)={}^{\phi }{\tilde {V}}_{123..}={\frac {V-V_{0}}{n_{1}+n_{2}+n_{3}+...}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/bc7d81e533b0c10f9d8be22fd5658206aa53e45c" style="height: 5.676ex; vertical-align: -2.171ex; width: 48.521ex;" /></span>,</dd></dl>
<p>The sum of products molalities – apparent molar volumes of solutes in
their binary solutions equals the product between the sum of molalities
of solutes and apparent molar volume in ternary of multicomponent
solution mentioned above.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>123..</mn>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>+</mo>
<mo>.</mo>
<mo>.</mo>
<mo>.</mo>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>b</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>3</mn>
</mrow>
</msub>
<mo>+</mo>
<mo>.</mo>
<mo>.</mo>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{123..}(b_{1}+b_{2}+b_{3}+...)=b_{1}{}^{\phi }{\tilde {V}}_{1}+b_{2}{}^{\phi }{\tilde {V}}_{2}+b_{3}{}^{\phi }{\tilde {V}}_{3}+...}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8db1627a78db95c24d828d2d36c4356bc950021b" style="height: 3.176ex; vertical-align: -0.838ex; width: 56.785ex;" /></span>,</dd></dl>
<p>Another method is to treat the ternary system as <i>pseudobinary</i>
and define the apparent molar volume of each solute with reference to a
binary system containing both other components: water and the other
solute. The apparent molar volumes of each of the two solutes are then
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<mi>V</mi>
<mo stretchy="false">(</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>v</mi>
<mi>e</mi>
<mi>n</mi>
<mi>t</mi>
<mo>+</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>u</mi>
<mi>t</mi>
<mi>e</mi>
<mtext> </mtext>
<mn>2</mn>
<mo stretchy="false">)</mo>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{1}={\frac {V-V(solvent+solute\ 2)}{n_{1}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1ea71a65d856746edb077a9f2b3fda54c4917cf0" style="height: 6.009ex; vertical-align: -2.171ex; width: 34.317ex;" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<mi>V</mi>
<mo stretchy="false">(</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>v</mi>
<mi>e</mi>
<mi>n</mi>
<mi>t</mi>
<mo>+</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>u</mi>
<mi>t</mi>
<mi>e</mi>
<mtext> </mtext>
<mn>1</mn>
<mo stretchy="false">)</mo>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{2}={\frac {V-V(solvent+solute\ 1)}{n_{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7a0a017922f02fcc0c8395a8c783c941056ffd3a" style="height: 6.009ex; vertical-align: -2.171ex; width: 34.317ex;" /></span></dd></dl>
<p>The apparent molar volume of the solvent is:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>0</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<mi>V</mi>
<mo stretchy="false">(</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>u</mi>
<mi>t</mi>
<mi>e</mi>
<mtext> </mtext>
<mn>1</mn>
<mo>+</mo>
<mi>s</mi>
<mi>o</mi>
<mi>l</mi>
<mi>u</mi>
<mi>t</mi>
<mi>e</mi>
<mtext> </mtext>
<mn>2</mn>
<mo stretchy="false">)</mo>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>0</mn>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{0}={\frac {V-V(solute\ 1+solute\ 2)}{n_{0}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0c8bdb05ad833fcccc70c94da48df572a7808c7e" style="height: 6.009ex; vertical-align: -2.171ex; width: 34.867ex;" /></span></dd></dl>
<p>However, this is an unsatisfactory description of volumetric properties.
</p><p>The apparent molar volume of two components or solutes considered as one pseudocomponent <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>12</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{12}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ae47b87dacfb89229627ac7f4f076a941395b5ae" style="height: 3.009ex; vertical-align: -0.671ex; width: 4.875ex;" /></span> or <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>ϕ</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mi>i</mi>
<mi>j</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{\phi }{\tilde {V}}_{ij}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e87a8c7b7466b62613a6999e1d5e4f0d56b2e369" style="height: 3.343ex; vertical-align: -1.005ex; width: 4.476ex;" /></span> is not to be confused with volumes of partial binary mixtures with one common component <i>V<sub>ij</sub></i>, <i>V<sub>jk</sub></i> which mixed in a certain <a href="https://en.wikipedia.org/wiki/Mixing_ratio" title="Mixing ratio">mixing ratio</a> form a certain ternary mixture <i>V</i> or <i>V<sub>ijk</sub></i>.
</p><p>Of course the complement volume of a component in respect to
other components of the mixture can be defined as a difference between
the volume of the mixture and the volume of a binary submixture of a
given composition like:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mrow>
</mrow>
<mrow>
<mi>c</mi>
</mrow>
</msup>
<msub>
<mrow>
<mrow>
<mover>
<mi>V</mi>
<mo stretchy="false">~</mo>
</mover>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi>V</mi>
<mo>−</mo>
<msub>
<mi>V</mi>
<mrow>
<mn>01</mn>
</mrow>
</msub>
</mrow>
<msub>
<mi>n</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {}^{c}{\tilde {V}}_{2}={\frac {V-V_{01}}{n_{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/32f30f05bc49a52d2b93f8ab057e8234a1bac639" style="height: 5.676ex; vertical-align: -2.171ex; width: 15.579ex;" /></span></dd></dl>
<p>There are situations when there is no rigorous way to define which is
solvent and which is solute like in the case of liquid mixtures (say
water and ethanol) that can dissolve or not a solid like sugar or salt.
In these cases apparent molar properties can and must be ascribed to all
components of the mixture.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-17695135654617639342024-03-16T13:08:00.002-04:002024-03-16T13:08:22.059-04:00Citric acid<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
</div>
<div id="contentSub"><div id="mw-content-subtitle"></div></div>
<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en">
<div class="hatnote navigation-not-searchable" role="note"><a href="https://en.wikipedia.org/wiki/Citric_acid">https://en.wikipedia.org/wiki/Citric_acid</a><br /></div>
<p>
</p>
<table class="infobox ib-chembox">
<caption>Citric acid
</caption>
<tbody><tr>
<td class="borderless" colspan="2" style="text-align: center;">
<table border="0" style="display: inline-table; width: 100%;">
<tbody><tr>
<td style="border-right: 1px solid #aaa; width: 50%;"><figure class="mw-halign-center"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Zitronens%C3%A4ure_-_Citric_acid.svg" title="Stereo skeletal formula of citric acid"><img alt="Stereo skeletal formula of citric acid" class="mw-file-element" data-file-height="116" data-file-width="256" height="68" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Zitronens%C3%A4ure_-_Citric_acid.svg/150px-Zitronens%C3%A4ure_-_Citric_acid.svg.png" width="150" /></a></figure>
</td>
<td style="width: 50%;"><figure class="mw-halign-center"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Citric-acid-3D-balls.png" title="Ball-and-stick model of citric acid"><img alt="Ball-and-stick model of citric acid" class="mw-file-element" data-file-height="635" data-file-width="1100" height="87" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Citric-acid-3D-balls.png/150px-Citric-acid-3D-balls.png" width="150" /></a></figure>
</td></tr></tbody></table>
</td></tr>
<tr>
<td colspan="2" style="padding: 2px; text-align: center;"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Zitronens%C3%A4ure_Kristallzucht.jpg" title="Crystal sample from the saturated citric acid solution."><img alt="Crystal sample from the saturated citric acid solution." class="mw-file-element" data-file-height="1503" data-file-width="1822" height="330" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Zitronens%C3%A4ure_Kristallzucht.jpg/320px-Zitronens%C3%A4ure_Kristallzucht.jpg" width="400" /></a></span>
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Names
</th></tr>
<tr>
<td colspan="2" style="text-align: left;"><a href="https://en.wikipedia.org/wiki/Chemical_nomenclature" title="Chemical nomenclature">IUPAC name</a>
<div style="max-width: 22em; padding-left: 1.7em; word-wrap: break-word;">Citric acid</div>
</td></tr>
<tr>
<td colspan="2" style="text-align: left;"><a href="https://en.wikipedia.org/wiki/Preferred_IUPAC_name" title="Preferred IUPAC name">Preferred IUPAC name</a>
<div style="max-width: 22em; padding-left: 1.7em; word-wrap: break-word;"><div style="display: inline-block; line-height: 1.2em; max-width: 22em; padding: .1em 0;">2-Hydroxypropane-1,2,3-tricarboxylic acid</div></div>
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Identifiers
</th></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/CAS_Registry_Number" title="CAS Registry Number">CAS Number</a></div>
</td>
<td><div class="plainlist"><ul><li><span title="commonchemistry.cas.org"><a class="external text" href="https://commonchemistry.cas.org/detail?cas_rn=77-92-9" rel="nofollow">77-92-9</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">3D model (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/JSmol" title="JSmol">JSmol</a>)</div>
</td>
<td><div class="plainlist"><ul><li><span title="chemapps.stolaf.edu (3D interactive model)"><a class="external text" href="https://chemapps.stolaf.edu/jmol/jmol.php?model=OC%28%3DO%29CC%28O%29%28C%28%3DO%29O%29CC%28%3DO%29O" rel="nofollow">Interactive image</a></span></li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/ChEBI" title="ChEBI">ChEBI</a>
</td>
<td><div class="plainlist"><ul><li><span title="www.ebi.ac.uk"><a class="external text" href="https://www.ebi.ac.uk/chebi/searchId.do?chebiId=30769" rel="nofollow">CHEBI:30769</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/ChEMBL" title="ChEMBL">ChEMBL</a>
</td>
<td><div class="plainlist"><ul><li><span title="www.ebi.ac.uk"><a class="external text" href="https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/ChEMBL1261" rel="nofollow">ChEMBL1261</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/ChemSpider" title="ChemSpider">ChemSpider</a>
</td>
<td><div class="plainlist"><ul><li><span title="www.chemspider.com"><a class="external text" href="https://www.chemspider.com/Chemical-Structure.305.html" rel="nofollow">305</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/DrugBank" title="DrugBank">DrugBank</a>
</td>
<td><div class="plainlist"><ul><li><span title="www.drugbank.ca"><a class="external text" href="https://www.drugbank.ca/drugs/DB04272" rel="nofollow">DB04272</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/ECHA_InfoCard" title="ECHA InfoCard"><span title="echa.europa.eu">ECHA InfoCard</span></a>
</td>
<td><a class="external text" href="https://echa.europa.eu/substance-information/-/substanceinfo/100.000.973" rel="nofollow">100.000.973</a> <span class="mw-valign-text-top noprint"><a href="https://www.wikidata.org/wiki/Q159683#P2566" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" class="mw-file-element" data-file-height="20" data-file-width="20" height="10" src="https://upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" width="10" /></a></span>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/European_Community_number" title="European Community number"><span title="European Community number (chemical identifier)">EC Number</span></a>
</td>
<td><div class="plainlist"><ul><li>201-069-1</li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/E_number" title="E number"><span title="E number (food additive code)">E number</span></a>
</td>
<td>E330 <a href="https://en.wikipedia.org/wiki/E_number#E300–E399" title="E number">(antioxidants, ...)</a>
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a class="mw-redirect" href="https://en.wikipedia.org/wiki/IUPHAR/BPS" title="IUPHAR/BPS">IUPHAR/BPS</a></div>
</td>
<td><div class="plainlist"><ul><li><span title="www.guidetopharmacology.org"><a class="external text" href="http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?tab=summary&ligandId=2478" rel="nofollow">2478</a></span></li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/KEGG" title="KEGG">KEGG</a>
</td>
<td><div class="plainlist"><ul><li><span title="www.kegg.jp"><a class="external text" href="https://www.kegg.jp/entry/D00037" rel="nofollow">D00037</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/PubChem" title="PubChem">PubChem</a> <abbr title="Compound ID">CID</abbr></div>
</td>
<td><div class="plainlist"><ul><li><span title="pubchem.ncbi.nlm.nih.gov"><a class="external text" href="https://pubchem.ncbi.nlm.nih.gov/compound/311" rel="nofollow">311</a></span></li><li><span title="pubchem.ncbi.nlm.nih.gov"><a class="external text" href="https://pubchem.ncbi.nlm.nih.gov/compound/22230" rel="nofollow">22230</a></span> (monohydrate)</li></ul></div>
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/RTECS" title="RTECS">RTECS number</a>
</td>
<td><div class="plainlist"><ul><li>GE7350000</li></ul></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Unique_Ingredient_Identifier" title="Unique Ingredient Identifier">UNII</a>
</td>
<td><div class="plainlist"><ul><li><span title="precision.fda.gov"><a class="external text" href="https://precision.fda.gov/uniisearch/srs/unii/XF417D3PSL" rel="nofollow">XF417D3PSL</a></span><sup> <span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span></sup></li></ul></div>
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/CompTox_Chemicals_Dashboard" title="CompTox Chemicals Dashboard">CompTox Dashboard</a> <span style="font-weight: normal;">(<abbr title="U.S. Environmental Protection Agency">EPA</abbr>)</span></div>
</td>
<td><div class="plainlist"><ul><li><span title="comptox.epa.gov"><a class="external text" href="https://comptox.epa.gov/dashboard/chemical/details/DTXSID3020332" rel="nofollow">DTXSID3020332</a> <span class="mw-valign-text-top noprint"><a href="https://www.wikidata.org/wiki/Q159683#P3117" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" class="mw-file-element" data-file-height="20" data-file-width="20" height="10" src="https://upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" width="10" /></a></span></span></li></ul></div>
</td></tr>
<tr>
<td colspan="2"><div class="collapsible-list mw-collapsible mw-collapsed mw-made-collapsible" style="text-align: left;"></div><br /></td></tr></tbody></table></div></div></div><table class="infobox ib-chembox"><tbody><tr><td colspan="2"><div class="collapsible-list mw-collapsible mw-collapsed mw-made-collapsible" style="text-align: left;"><div style="background: transparent; font-weight: bold; font-weight: normal; line-height: 1.6em; text-align: left;"><div><a href="https://en.wikipedia.org/wiki/International_Chemical_Identifier" title="International Chemical Identifier">InChI</a></div></div>
</div>
</td></tr>
<tr>
<td colspan="2"><div class="collapsible-list mw-collapsible mw-collapsed mw-made-collapsible" style="text-align: left;"></div><br /></td></tr></tbody></table><table class="infobox ib-chembox"><tbody><tr><td colspan="2"><div class="collapsible-list mw-collapsible mw-collapsed mw-made-collapsible" style="text-align: left;"><div style="background: transparent; font-weight: bold; font-weight: normal; line-height: 1.6em; text-align: left;"><div><a href="https://en.wikipedia.org/wiki/Simplified_molecular-input_line-entry_system" title="Simplified molecular-input line-entry system">SMILES</a></div></div>
</div>
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Properties
</th></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Chemical_formula" title="Chemical formula">Chemical formula</a></div>
</td>
<td><span title="Carbon">C</span><sub>6</sub><span title="Hydrogen">H</span><sub>8</sub><span title="Oxygen">O</span><sub>7</sub>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Molar_mass" title="Molar mass">Molar mass</a>
</td>
<td>192.123<span class="nowrap"> </span>g/mol (anhydrous), 210.14<span class="nowrap"> </span>g/mol (monohydrate)<sup class="reference" id="cite_ref-2"><a href="https://en.wikipedia.org/wiki/Citric_acid#cite_note-2">[2]</a></sup>
</td></tr>
<tr>
<td>Appearance
</td>
<td>white solid
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Odor" title="Odor">Odor</a>
</td>
<td>Odorless
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Density" title="Density">Density</a>
</td>
<td>1.665<span class="nowrap"> </span>g/cm<sup>3</sup> (anhydrous)<br /> 1.542<span class="nowrap"> </span>g/cm<sup>3</sup> (18<span class="nowrap"> </span>°C, monohydrate)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Melting_point" title="Melting point">Melting point</a>
</td>
<td>156 °C (313 °F; 429 K)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Boiling_point" title="Boiling point">Boiling point</a>
</td>
<td>310 °C (590 °F; 583 K) decomposes from 175<span class="nowrap"> </span>°C<sup class="reference" id="cite_ref-chemister_3-0"><a href="https://en.wikipedia.org/wiki/Citric_acid#cite_note-chemister-3">[3]</a></sup>
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Aqueous_solution" title="Aqueous solution">Solubility in water</a></div>
</td>
<td>54%<span class="nowrap"> </span>w/w (10<span class="nowrap"> </span>°C)<br /> 59.2%<span class="nowrap"> </span>w/w (20<span class="nowrap"> </span>°C)<br /> 64.3%<span class="nowrap"> </span>w/w (30<span class="nowrap"> </span>°C)<br /> 68.6%<span class="nowrap"> </span>w/w (40<span class="nowrap"> </span>°C)<br /> 70.9%<span class="nowrap"> </span>w/w (50<span class="nowrap"> </span>°C)<br /> 73.5%<span class="nowrap"> </span>w/w (60<span class="nowrap"> </span>°C)<br /> 76.2%<span class="nowrap"> </span>w/w (70<span class="nowrap"> </span>°C)<br /> 78.8%<span class="nowrap"> </span>w/w (80<span class="nowrap"> </span>°C)<br /> 81.4%<span class="nowrap"> </span>w/w (90<span class="nowrap"> </span>°C)<br /> 84%<span class="nowrap"> </span>w/w (100<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a>
</td>
<td>Soluble in <a href="https://en.wikipedia.org/wiki/Acetone" title="Acetone">acetone</a>, <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">alcohol</a>, <a href="https://en.wikipedia.org/wiki/Diethyl_ether" title="Diethyl ether">ether</a>, <a href="https://en.wikipedia.org/wiki/Ethyl_acetate" title="Ethyl acetate">ethyl acetate</a>, <a href="https://en.wikipedia.org/wiki/Dimethyl_sulfoxide" title="Dimethyl sulfoxide">DMSO</a><br /> Insoluble in <a href="https://en.wikipedia.org/wiki/Benzene" title="Benzene"><span class="chemf nowrap">C<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">6</sub></span>H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">6</sub></span></span></a>, <a href="https://en.wikipedia.org/wiki/Chloroform" title="Chloroform">CHCl<sub>3</sub></a>, <a href="https://en.wikipedia.org/wiki/Carbon_disulfide" title="Carbon disulfide">CS<sub>2</sub></a>, <a href="https://en.wikipedia.org/wiki/Toluene" title="Toluene">toluene</a>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a> in <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">ethanol</a>
</td>
<td>62<span class="nowrap"> </span>g/100 g (25<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a> in <a href="https://en.wikipedia.org/wiki/Amyl_acetate" title="Amyl acetate">amyl acetate</a>
</td>
<td>4.41<span class="nowrap"> </span>g/100 g (25<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a> in <a href="https://en.wikipedia.org/wiki/Diethyl_ether" title="Diethyl ether">diethyl ether</a>
</td>
<td>1.05<span class="nowrap"> </span>g/100 g (25<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Solubility" title="Solubility">Solubility</a> in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/1,4-dioxane" title="1,4-dioxane">1,4-dioxane</a>
</td>
<td>35.9<span class="nowrap"> </span>g/100 g (25<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Partition_coefficient" title="Partition coefficient">log <i>P</i></a>
</td>
<td>−1.64
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant" title="Acid dissociation constant">Acidity</a> (p<i>K</i><sub>a</sub>)
</td>
<td>p<i>K</i><sub>a1</sub> = 3.13<br /> p<i>K</i><sub>a2</sub> = 4.76<br /> p<i>K</i><sub>a3</sub> = 6.39, 6.40<br />p<i>K</i><sub>a4</sub> = 14.4
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Refractive_index" title="Refractive index">Refractive index</a> (<i>n</i><sub>D</sub>)</div>
</td>
<td>1.493–1.509 (20<span class="nowrap"> </span>°C)<br /> 1.46 (150<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Viscosity" title="Viscosity">Viscosity</a>
</td>
<td>6.5<span class="nowrap"> </span>cP (50% <abbr title="aqueous solution">aq. sol.</abbr>)
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Structure
</th></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Crystal_structure" title="Crystal structure">Crystal structure</a></div>
</td>
<td>Monoclinic
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Thermochemistry
</th></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Heat_capacity" title="Heat capacity">Heat capacity</a> <span style="background-color: transparent; color: black; font-family: sans-serif; font-size: 112%;">(<i>C</i>)</span></div>
</td>
<td>226.51<span class="nowrap"> </span>J/(mol·K) (26.85<span class="nowrap"> </span>°C)
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Standard_molar_entropy" title="Standard molar entropy">Std molar<br />entropy</a> <span style="background-color: transparent; color: black; font-family: sans-serif; font-size: 112%;">(<i>S</i><sup>⦵</sup><sub>298</sub>)</span></div>
</td>
<td>252.1<span class="nowrap"> </span>J/(mol·K)
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation" title="Standard enthalpy change of formation">Std enthalpy of<br />formation</a> <span style="background-color: transparent; color: black; font-family: sans-serif; font-size: 112%;">(Δ<sub>f</sub><i>H</i><sup>⦵</sup><sub>298</sub>)</span></div>
</td>
<td>−1543.8<span class="nowrap"> </span>kJ/mol
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Heat_of_combustion#Higher_heating_value" title="Heat of combustion">Heat of combustion, higher value</a> (HHV)</div>
</td>
<td>1985.3 kJ/mol (474.5 kcal/mol, 2.47 kcal/g), 1960.6<span class="nowrap"> </span>kJ/mol<br /> 1972.34 kJ/mol (471.4 kcal/mol, 2.24 kcal/g) (monohydrate)
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Pharmacology
</th></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Anatomical_Therapeutic_Chemical_Classification_System" title="Anatomical Therapeutic Chemical Classification System">ATC code</a></div>
</td>
<td><a href="https://en.wikipedia.org/wiki/ATC_code_A09" title="ATC code A09">A09AB04</a> (<span title="www.whocc.no"><a class="external text" href="https://www.whocc.no/atc_ddd_index/?code=A09AB04" rel="nofollow">WHO</a></span>)
</td></tr>
<tr>
<th colspan="2" style="background: #f8eaba; text-align: center;">Hazards
</th></tr>
<tr>
<td colspan="2" style="background-color: #eaeaea; text-align: left;"><b><a href="https://en.wikipedia.org/wiki/Occupational_safety_and_health" title="Occupational safety and health">Occupational safety and health</a></b> (OHS/OSH):
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Main hazards</div>
</td>
<td>Skin and eye irritant
</td></tr>
<tr>
<td colspan="2" style="background-color: #eaeaea; text-align: left;"><a href="https://en.wikipedia.org/wiki/Globally_Harmonized_System_of_Classification_and_Labelling_of_Chemicals" title="Globally Harmonized System of Classification and Labelling of Chemicals"><b>GHS</b> labelling</a>:
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/GHS_hazard_pictograms" title="GHS hazard pictograms">Pictograms</a></div>
</td>
<td><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:GHS-pictogram-acid.svg" title="GHS05: Corrosive"><img alt="GHS05: Corrosive" class="mw-file-element" data-file-height="724" data-file-width="724" height="50" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/GHS-pictogram-acid.svg/50px-GHS-pictogram-acid.svg.png" width="50" /></a></span><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:GHS-pictogram-exclam.svg" title="GHS07: Exclamation mark"><img alt="GHS07: Exclamation mark" class="mw-file-element" data-file-height="512" data-file-width="512" height="50" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/GHS-pictogram-exclam.svg/50px-GHS-pictogram-exclam.svg.png" width="50" /></a></span>
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Globally_Harmonized_System_of_Classification_and_Labelling_of_Chemicals#Signal_word" title="Globally Harmonized System of Classification and Labelling of Chemicals">Signal word</a></div>
</td>
<td><b>Warning</b>
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/GHS_hazard_statements" title="GHS hazard statements">Hazard statements</a></div>
</td>
<td><abbr class="abbr" title="H290: May be corrosive to metals">H290</abbr>, <abbr class="abbr" title="H319: Causes serious eye irritation">H319</abbr>, <abbr class="abbr" title="H315: Causes skin irritation">H315</abbr>
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/GHS_precautionary_statements" title="GHS precautionary statements">Precautionary statements</a></div>
</td>
<td><abbr class="abbr" title="P305+P351+P338: IF IN EYES: Rinse continuously with water for several minutes. Remove contact lenses if present and easy to do. Continue rinsing.">P305+P351+P338</abbr>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/NFPA_704" title="NFPA 704"><b>NFPA 704</b></a> (fire diamond)
</td>
<td><div class="nfpa-704-diamond"><div class="nfpa-704-diamond-container"><div class="nfpa-704-diamond-images nounderlines">
<div class="nfpa-704-diamond-map"><figure class="noresize"><span><img alt="NFPA 704 four-colored diamond" class="mw-file-element" data-file-height="512" data-file-width="512" height="80" src="https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/NFPA_704.svg/80px-NFPA_704.svg.png" usemap="#ImageMap_482e25fdfe95519d" width="80" /></span><map name="ImageMap_482e25fdfe95519d"><area alt="Health 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroform" coords="23,23,47,47,23,70,0,47" href="https://en.wikipedia.org/wiki/NFPA_704#Blue" shape="poly" title="Health 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroform"></area><area alt="Flammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oil" coords="47,0,70,23,47,47,23,23" href="https://en.wikipedia.org/wiki/NFPA_704#Red" shape="poly" title="Flammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oil"></area><area alt="Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen" coords="70,23,94,47,70,70,47,47" href="https://en.wikipedia.org/wiki/NFPA_704#Yellow" shape="poly" title="Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen"></area><area alt="Special hazards (white): no code" coords="47,47,70,70,47,94,23,70" href="https://en.wikipedia.org/wiki/NFPA_704#White" shape="poly" title="Special hazards (white): no code"></area></map></figure></div><div class="nfpa-704-diamond-code nfpa-704-diamond-blue">
<a href="https://en.wikipedia.org/wiki/NFPA_704#Blue" title="NFPA 704"><span title="Health 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroform">2</span></a></div><div class="nfpa-704-diamond-code nfpa-704-diamond-red">
<a href="https://en.wikipedia.org/wiki/NFPA_704#Red" title="NFPA 704"><span title="Flammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oil">1</span></a></div><div class="nfpa-704-diamond-code nfpa-704-diamond-yellow">
<a href="https://en.wikipedia.org/wiki/NFPA_704#Yellow" title="NFPA 704"><span title="Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen">0</span></a></div></div></div></div>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Flash_point" title="Flash point">Flash point</a>
</td>
<td>155 °C (311 °F; 428 K)
</td></tr>
<tr>
<td><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="https://en.wikipedia.org/wiki/Autoignition_temperature" title="Autoignition temperature">Autoignition<br />temperature</a></div>
</td>
<td>345 °C (653 °F; 618 K)
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Explosive_limit" title="Explosive limit">Explosive limits</a>
</td>
<td>8%
</td></tr>
<tr>
<td colspan="2" style="background-color: #eaeaea; text-align: left;"><b>Lethal dose</b> or concentration (LD, LC):
</td></tr>
<tr style="background: #f1f1f1;">
<td style="padding-left: 1em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">LD<sub>50</sub> (<a href="https://en.wikipedia.org/wiki/Lethal_dose#LD50" title="Lethal dose">median dose</a>)</div>
</td>
<td>3000<span class="nowrap"> </span>mg/kg (rats, oral)
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Safety_data_sheet" title="Safety data sheet">Safety data sheet</a> (SDS)
</td>
<td><a class="external text" href="http://www.hmdb.ca/system/metabolites/msds/000/000/065/original/HMDB00094.pdf?1358893891" rel="nofollow">HMDB</a>
</td></tr>
<tr>
<td colspan="2" style="background: #f8eaba; border: 1px solid #a2a9b1; text-align: left;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Except where otherwise noted, data are given for materials in their <a href="https://en.wikipedia.org/wiki/Standard_state" title="Standard state">standard state</a> (at 25 °C [77 °F], 100 kPa).</div>
<div style="margin-top: 0.3em;"><div style="text-align: center;"><span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="12" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/12px-Yes_check.svg.png" width="12" /></span></span> <span class="reflink plainlinks nourlexpansion"><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Special:ComparePages&rev1=477313834&page2=Citric+acid">verify</a></span> (<a href="https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Chemicals/Chembox_validation" title="Wikipedia:WikiProject Chemicals/Chembox validation">what is</a> <sup><span><span><img alt="check" class="mw-file-element" data-file-height="600" data-file-width="600" height="7" src="https://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/7px-Yes_check.svg.png" width="7" /></span></span><span><span><img alt="☒" class="mw-file-element" data-file-height="600" data-file-width="525" height="8" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/X_mark.svg/7px-X_mark.svg.png" width="7" /></span></span></sup> ?)
</div></div>
<div style="margin-top: 0.3em; text-align: center;"><a href="https://en.wikipedia.org/wiki/Wikipedia:Chemical_infobox#References" title="Wikipedia:Chemical infobox">Infobox references</a></div>
</td></tr>
</tbody></table>
<p><b>Citric acid</b> is an <a href="https://en.wikipedia.org/wiki/Organic_compound" title="Organic compound">organic compound</a> with the <a href="https://en.wikipedia.org/wiki/Chemical_formula" title="Chemical formula">chemical formula</a> HOC(CO<sub>2</sub>H)(CH<sub>2</sub>CO<sub>2</sub>H)<sub>2</sub>. It is a <a href="https://en.wikipedia.org/wiki/Transparency_and_translucency" title="Transparency and translucency">colorless</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Weak_acid" title="Weak acid">weak</a> <a href="https://en.wikipedia.org/wiki/Organic_acid" title="Organic acid">organic acid</a>. It occurs naturally in <a href="https://en.wikipedia.org/wiki/Citrus" title="Citrus">citrus fruits</a>. In <a href="https://en.wikipedia.org/wiki/Biochemistry" title="Biochemistry">biochemistry</a>, it is an intermediate in the <a href="https://en.wikipedia.org/wiki/Citric_acid_cycle" title="Citric acid cycle">citric acid cycle</a>, which occurs in the <a href="https://en.wikipedia.org/wiki/Metabolism" title="Metabolism">metabolism</a> of all <a href="https://en.wikipedia.org/wiki/Aerobic_organism" title="Aerobic organism">aerobic organisms</a>.
</p><p>More than two million tons of citric acid <a href="https://en.wikipedia.org/wiki/Commodity_chemicals" title="Commodity chemicals">are manufactured</a> every year. It is used widely as an <a href="https://en.wikipedia.org/wiki/Acidifier" title="Acidifier">acidifier</a>, as a <a href="https://en.wikipedia.org/wiki/Flavoring" title="Flavoring">flavoring</a>, and a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chelating_agent" title="Chelating agent">chelating agent</a>.
</p><p>A <b>citrate</b> is a derivative of citric acid; that is, the <a href="https://en.wikipedia.org/wiki/Salt_(chemistry)" title="Salt (chemistry)">salts</a>, <a href="https://en.wikipedia.org/wiki/Ester" title="Ester">esters</a>, and the <a href="https://en.wikipedia.org/wiki/Polyatomic_ion" title="Polyatomic ion">polyatomic anion</a> found in solution. An example of the former, a salt is <a href="https://en.wikipedia.org/wiki/Trisodium_citrate" title="Trisodium citrate">trisodium citrate</a>; an ester is <a href="https://en.wikipedia.org/wiki/Triethyl_citrate" title="Triethyl citrate">triethyl citrate</a>. When part of a salt, the formula of the citrate anion is written as <span class="chemf nowrap">C<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">6</sub></span>H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">5</sub></span>O<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">7</sub></span></span> or <span class="chemf nowrap">C<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span>H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">5</sub></span>O(COO)<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>.
</p>
<h2><span class="mw-headline" id="Natural_occurrence_and_industrial_production">Natural occurrence and industrial production</span></h2><figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Citrus_fruits.jpg"><img alt="" class="mw-file-element" data-file-height="1779" data-file-width="2700" height="264" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Citrus_fruits.jpg/220px-Citrus_fruits.jpg" width="400" /></a><figcaption>Lemons, oranges, limes, and other citrus fruits contain high concentrations of citric acid.</figcaption></figure>
<p>Citric acid occurs in a variety of fruits and vegetables, most notably <a href="https://en.wikipedia.org/wiki/Citrus" title="Citrus">citrus fruits</a>. <a href="https://en.wikipedia.org/wiki/Lemon" title="Lemon">Lemons</a> and <a href="https://en.wikipedia.org/wiki/Lime_(fruit)" title="Lime (fruit)">limes</a>
have particularly high concentrations of the acid; it can constitute as
much as 8% of the dry weight of these fruits (about 47 g/L in the
juices<sup class="reference" id="cite_ref-12"><a href="https://en.wikipedia.org/wiki/Citric_acid#cite_note-12">[12]</a></sup>). The concentrations of citric acid in citrus fruits range from 0.005 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Molarity" title="Molarity">mol/L</a> for oranges and grapefruits to 0.30 mol/L in lemons and limes; these values vary within species depending upon the <a href="https://en.wikipedia.org/wiki/Cultivar" title="Cultivar">cultivar</a> and the circumstances under which the fruit was grown.
</p><p>Citric acid was first isolated in 1784 by the chemist <a href="https://en.wikipedia.org/wiki/Carl_Wilhelm_Scheele" title="Carl Wilhelm Scheele">Carl Wilhelm Scheele</a>, who crystallized it from lemon juice.
</p><p>Industrial-scale citric acid production first began in 1890 based on the Italian <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Citrus_fruit" title="Citrus fruit">citrus fruit</a> industry, where the juice was treated with hydrated lime (<a href="https://en.wikipedia.org/wiki/Calcium_hydroxide" title="Calcium hydroxide">calcium hydroxide</a>) to precipitate <a href="https://en.wikipedia.org/wiki/Calcium_citrate" title="Calcium citrate">calcium citrate</a>, which was isolated and converted back to the acid using diluted <a href="https://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid">sulfuric acid</a>. In 1893, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carl_Wehmer_(chemist)" title="Carl Wehmer (chemist)">C. Wehmer</a> discovered <i><a href="https://en.wikipedia.org/wiki/Penicillium" title="Penicillium">Penicillium</a></i> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mold_(fungus)" title="Mold (fungus)">mold</a> could produce citric acid from sugar.
However, microbial production of citric acid did not become
industrially important until World War I disrupted Italian citrus
exports.
</p><p>In 1917, American food chemist James Currie discovered that certain strains of the mold <i><a href="https://en.wikipedia.org/wiki/Aspergillus_niger" title="Aspergillus niger">Aspergillus niger</a></i> could be efficient citric acid producers, and the pharmaceutical company <a href="https://en.wikipedia.org/wiki/Pfizer" title="Pfizer">Pfizer</a> began industrial-level production using this technique two years later, followed by <a href="https://en.wikipedia.org/wiki/Citrique_Belge" title="Citrique Belge">Citrique Belge</a> in 1929.
In this production technique, which is still the major industrial route to citric acid used today, cultures of <i>Aspergillus niger</i> are fed on a <a href="https://en.wikipedia.org/wiki/Sucrose" title="Sucrose">sucrose</a> or <a href="https://en.wikipedia.org/wiki/Glucose" title="Glucose">glucose</a>-containing medium to produce citric acid. The source of sugar is <a href="https://en.wikipedia.org/wiki/Corn_steep_liquor" title="Corn steep liquor">corn steep liquor</a>, <a href="https://en.wikipedia.org/wiki/Molasses" title="Molasses">molasses</a>, hydrolyzed <a href="https://en.wikipedia.org/wiki/Corn_starch" title="Corn starch">corn starch</a>, or other inexpensive, <a href="https://en.wikipedia.org/wiki/Carbohydrate" title="Carbohydrate">carbohydrate</a> solution. After the mold is filtered out of the resulting <a href="https://en.wikipedia.org/wiki/Suspension_(chemistry)" title="Suspension (chemistry)">suspension</a>, citric acid is isolated by <a href="https://en.wikipedia.org/wiki/Precipitation_(chemistry)" title="Precipitation (chemistry)">precipitating</a>
it with calcium hydroxide to yield calcium citrate salt, from which
citric acid is regenerated by treatment with sulfuric acid, as in the
direct extraction from citrus fruit juice.
</p><p>In 1977, a patent was granted to <a href="https://en.wikipedia.org/wiki/Lever_Brothers" title="Lever Brothers">Lever Brothers</a>
for the chemical synthesis of citric acid starting either from aconitic
or isocitrate (also called alloisocitrate) calcium salts under high
pressure conditions; this produced citric acid in near quantitative
conversion under what appeared to be a reverse, non-enzymatic <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Krebs_cycle_reaction" title="Krebs cycle reaction">Krebs cycle reaction</a>.
</p><p>Global production was in excess of 2,000,000 tons in 2018. More than 50% of this volume was produced in China. More than 50% was used as an <a href="https://en.wikipedia.org/wiki/Acidity_regulator" title="Acidity regulator">acidity regulator</a>
in beverages, some 20% in other food applications, 20% for detergent
applications, and 10% for applications other than food, such as
cosmetics, pharmaceuticals, and in the chemical industry.
</p>
<h2><span class="mw-headline" id="Chemical_characteristics">Chemical characteristics</span></h2><figure class="mw-default-size mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Citric_acid_speciation.svg"><img class="mw-file-element" data-file-height="432" data-file-width="723" height="238" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Citric_acid_speciation.svg/220px-Citric_acid_speciation.svg.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Ion_speciation" title="Ion speciation">Speciation</a> diagram for a 10-millimolar solution of citric acid</figcaption></figure>
<p>Citric acid can be obtained as an <a href="https://en.wikipedia.org/wiki/Anhydrous" title="Anhydrous">anhydrous</a> (water-free) form or as a <a href="https://en.wikipedia.org/wiki/Hydrate" title="Hydrate">monohydrate</a>.
The anhydrous form crystallizes from hot water, while the monohydrate
forms when citric acid is crystallized from cold water. The monohydrate
can be converted to the anhydrous form at about 78 °C. Citric acid also
dissolves in absolute (anhydrous) <a href="https://en.wikipedia.org/wiki/Ethanol" title="Ethanol">ethanol</a> (76 parts of citric acid per 100 parts of ethanol) at 15 °C. It <a href="https://en.wikipedia.org/wiki/Decarboxylation" title="Decarboxylation">decomposes</a> with loss of carbon dioxide above about 175 °C.
</p><p>Citric acid is a tribasic <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acid</a>, with <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant" title="Acid dissociation constant">pK<sub>a</sub></a> values, extrapolated to zero ionic strength, of 3.128, 4.761, and 6.396 at 25 °C. The pK<sub>a</sub> of the hydroxyl group has been found, by means of <sup>13</sup>C NMR spectroscopy, to be 14.4.
The speciation diagram shows that solutions of citric acid are <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">buffer solutions</a>
between about pH 2 and pH 8. In biological systems around pH 7, the two
species present are the citrate ion and mono-hydrogen citrate ion. The
SSC 20X hybridization buffer is an example in common use. Tables compiled for biochemical studies are available.
</p><p>Conversely, the pH of a 1 mM solution of citric acid will be about 3.2. The pH of fruit juices from <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Citrus_fruit" title="Citrus fruit">citrus fruits</a>
like oranges and lemons depends on the citric acid concentration, with a
higher concentration of citric acid resulting in a lower pH.
</p><p><a href="https://en.wikipedia.org/wiki/Acid_salt" title="Acid salt">Acid salts</a> of citric acid can be prepared by careful adjustment of the pH before crystallizing the compound. See, for example, <a href="https://en.wikipedia.org/wiki/Sodium_citrate" title="Sodium citrate">sodium citrate</a>.
</p><p>The citrate ion forms complexes with metallic cations. The <a href="https://en.wikipedia.org/wiki/Stability_constants_of_complexes" title="Stability constants of complexes">stability constants</a> for the formation of these complexes are quite large because of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chelate_effect" title="Chelate effect">chelate effect</a>.
Consequently, it forms complexes even with alkali metal cations.
However, when a chelate complex is formed using all three carboxylate
groups, the chelate rings have 7 and 8 members, which are generally less
stable thermodynamically than smaller chelate rings. In consequence,
the hydroxyl group can be deprotonated, forming part of a more stable
5-membered ring, as in <a href="https://en.wikipedia.org/wiki/Ammonium_ferric_citrate" title="Ammonium ferric citrate">ammonium ferric citrate</a>, <span class="chemf nowrap">(NH<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span>)<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">5</sub></span>Fe(C<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">6</sub></span>H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span>O<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">7</sub></span>)<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span>·2<span class="chemf nowrap">H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span>O</span>.
</p><p>Citric acid can be <a href="https://en.wikipedia.org/wiki/Ester" title="Ester">esterified</a> at one or more of its three <a href="https://en.wikipedia.org/wiki/Carboxylic_acid" title="Carboxylic acid">carboxylic acid</a> groups to form any of a variety of mono-, di-, tri-, and mixed esters.
</p>
<h2><span class="mw-headline" id="Biochemistry">Biochemistry</span></h2><h3><span class="mw-headline" id="Citric_acid_cycle">Citric acid cycle</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Citric_acid_cycle" title="Citric acid cycle">Citric acid cycle</a></div>
<p>Citrate is an intermediate in the <a href="https://en.wikipedia.org/wiki/Citric_acid_cycle" title="Citric acid cycle">citric acid cycle</a>, also known as the TCA (<b>T</b>ri<b>C</b>arboxylic <b>A</b>cid) cycle or the Krebs cycle, a central metabolic pathway for animals, plants, and bacteria. <a href="https://en.wikipedia.org/wiki/Citrate_synthase" title="Citrate synthase">Citrate synthase</a> catalyzes the condensation of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Oxaloacetate" title="Oxaloacetate">oxaloacetate</a> with acetyl CoA to form citrate. Citrate then acts as the substrate for <a href="https://en.wikipedia.org/wiki/Aconitase" title="Aconitase">aconitase</a> and is converted into <a href="https://en.wikipedia.org/wiki/Aconitic_acid" title="Aconitic acid">aconitic acid</a>.
The cycle ends with regeneration of oxaloacetate. This series of
chemical reactions is the source of two-thirds of the food-derived
energy in higher organisms. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hans_Adolf_Krebs" title="Hans Adolf Krebs">Hans Adolf Krebs</a> received the 1953 <a href="https://en.wikipedia.org/wiki/Nobel_Prize_in_Physiology_or_Medicine" title="Nobel Prize in Physiology or Medicine">Nobel Prize in Physiology or Medicine</a> for the discovery.
</p><p>Some bacteria (notably <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/E._coli" title="E. coli">E. coli</a></i>)
can produce and consume citrate internally as part of their TCA cycle,
but are unable to use it as food, because they lack the enzymes required
to import it into the cell. After tens of thousands of evolutions in a
minimal glucose medium that also contained citrate during <a href="https://en.wikipedia.org/wiki/Richard_Lenski" title="Richard Lenski">Richard Lenski</a>'s <a href="https://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment" title="E. coli long-term evolution experiment">Long-Term Evolution Experiment</a>, a variant <i>E. coli</i> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Evolved" title="Evolved">evolved</a> with the ability to grow <a href="https://en.wikipedia.org/wiki/Aerobic_organism" title="Aerobic organism">aerobically</a> on citrate. <a href="https://en.wikipedia.org/wiki/Zachary_Blount" title="Zachary Blount">Zachary Blount</a>, a student of Lenski's, and colleagues studied these "Cit<sup>+</sup>" <i>E. coli</i> as a model for how novel <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Genetic_trait" title="Genetic trait">traits</a> evolve. They found evidence that, in this case, the innovation was caused by a rare duplication <a href="https://en.wikipedia.org/wiki/Mutation" title="Mutation">mutation</a>
due to the accumulation of several prior "potentiating" mutations, the
identity and effects of which are still under study. The evolution of
the Cit<sup>+</sup> trait has been considered a notable example of the role of historical contingency in evolution.
</p>
<h3><span class="mw-headline" id="Other_biological_roles">Other biological roles</span></h3><p>Citrate can be transported out of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mitochondria" title="Mitochondria">mitochondria</a> and into the cytoplasm, then broken down into <a href="https://en.wikipedia.org/wiki/Acetyl-CoA" title="Acetyl-CoA">acetyl-CoA</a> for <a href="https://en.wikipedia.org/wiki/Fatty_acid_synthesis" title="Fatty acid synthesis">fatty acid synthesis</a>, and into oxaloacetate. Citrate is a positive modulator of this conversion, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Allosterically" title="Allosterically">allosterically</a> regulates the enzyme <a href="https://en.wikipedia.org/wiki/Acetyl-CoA_carboxylase" title="Acetyl-CoA carboxylase">acetyl-CoA carboxylase</a>, which is the regulating enzyme in the conversion of acetyl-CoA into <a href="https://en.wikipedia.org/wiki/Malonyl-CoA" title="Malonyl-CoA">malonyl-CoA</a>
(the commitment step in fatty acid synthesis). In short, citrate is
transported into the cytoplasm, converted into acetyl-CoA, which is then
converted into malonyl-CoA by acetyl-CoA carboxylase, which is
allosterically modulated by citrate.
</p><p>High concentrations of cytosolic citrate can inhibit <a href="https://en.wikipedia.org/wiki/Phosphofructokinase" title="Phosphofructokinase">phosphofructokinase</a>, the catalyst of a rate-limiting step of <a href="https://en.wikipedia.org/wiki/Glycolysis" title="Glycolysis">glycolysis</a>.
This effect is advantageous: high concentrations of citrate indicate
that there is a large supply of biosynthetic precursor molecules, so
there is no need for phosphofructokinase to continue to send molecules
of its substrate, <a href="https://en.wikipedia.org/wiki/Fructose_6-phosphate" title="Fructose 6-phosphate">fructose 6-phosphate</a>, into glycolysis. Citrate acts by augmenting the inhibitory effect of high concentrations of <a href="https://en.wikipedia.org/wiki/Adenosine_triphosphate" title="Adenosine triphosphate">ATP</a>, another sign that there is no need to carry out glycolysis.
</p><p>Citrate is a vital component of bone, helping to regulate the size of <a href="https://en.wikipedia.org/wiki/Apatite" title="Apatite">apatite</a> crystals.
</p>
<h2><span class="mw-headline" id="Applications">Applications</span></h2><h3><span class="mw-headline" id="Food_and_drink">Food and drink</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lemon_pepper_preparation.jpg"><img class="mw-file-element" data-file-height="438" data-file-width="800" height="218" src="https://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Lemon_pepper_preparation.jpg/220px-Lemon_pepper_preparation.jpg" width="400" /></a><figcaption>Powdered citric acid being used to prepare <a href="https://en.wikipedia.org/wiki/Lemon_pepper" title="Lemon pepper">lemon pepper</a> seasoning</figcaption></figure>
<p>Because it is one of the stronger edible acids, the dominant use of
citric acid is as a flavoring and preservative in food and beverages,
especially soft drinks and candies. Within the <a href="https://en.wikipedia.org/wiki/European_Union" title="European Union">European Union</a> it is denoted by <a href="https://en.wikipedia.org/wiki/E_number" title="E number">E number</a> <b>E330</b>. Citrate salts of various metals are used to deliver those minerals in a biologically available form in many <a href="https://en.wikipedia.org/wiki/Dietary_supplement" title="Dietary supplement">dietary supplements</a>. Citric acid has 247 kcal per 100 g. In the United States the purity requirements for citric acid as a food additive are defined by the <a href="https://en.wikipedia.org/wiki/Food_Chemicals_Codex" title="Food Chemicals Codex">Food Chemicals Codex</a>, which is published by the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/United_States_Pharmacopoeia" title="United States Pharmacopoeia">United States Pharmacopoeia</a> (USP).
</p><p>Citric acid can be added to ice cream as an emulsifying agent to
keep fats from separating, to caramel to prevent sucrose
crystallization, or in recipes in place of fresh lemon juice. Citric
acid is used with <a href="https://en.wikipedia.org/wiki/Sodium_bicarbonate" title="Sodium bicarbonate">sodium bicarbonate</a> in a wide range of <a href="https://en.wikipedia.org/wiki/Effervescence" title="Effervescence">effervescent</a> formulae, both for ingestion (e.g., powders and tablets) and for personal care (<i>e.g.</i>, <a href="https://en.wikipedia.org/wiki/Bath_salts" title="Bath salts">bath salts</a>, <a href="https://en.wikipedia.org/wiki/Bath_bomb" title="Bath bomb">bath bombs</a>, and cleaning of <a href="https://en.wikipedia.org/wiki/Petroleum" title="Petroleum">grease</a>).
Citric acid sold in a dry powdered form is commonly sold in markets and
groceries as "sour salt", due to its physical resemblance to table
salt. It has use in culinary applications, as an alternative to vinegar
or lemon juice, where a pure acid is needed. Citric acid can be used in <a href="https://en.wikipedia.org/wiki/Food_coloring" title="Food coloring">food coloring</a> to balance the pH level of a normally basic dye.
</p>
<h3><span class="mw-headline" id="Cleaning_and_chelating_agent">Cleaning and chelating agent</span></h3><figure class="mw-halign-left"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Fe2CITdianion.svg"><img class="mw-file-element" data-file-height="145" data-file-width="129" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Fe2CITdianion.svg/144px-Fe2CITdianion.svg.png" width="356" /></a><figcaption>Structure of an iron(III) citrate complex</figcaption></figure>
<p>Citric acid is an excellent <a href="https://en.wikipedia.org/wiki/Chelation" title="Chelation">chelating agent</a>, binding metals by making them soluble. It is used to remove and discourage the buildup of <a href="https://en.wikipedia.org/wiki/Limescale" title="Limescale">limescale</a> from boilers and evaporators.
It can be used to treat water, which makes it useful in improving the
effectiveness of soaps and laundry detergents. By chelating the metals
in <a href="https://en.wikipedia.org/wiki/Hard_water" title="Hard water">hard water</a>,
it lets these cleaners produce foam and work better without need for
water softening. Citric acid is the active ingredient in some bathroom
and kitchen cleaning solutions. A solution with a six percent
concentration of citric acid will remove hard water stains from glass
without scrubbing. Citric acid can be used in shampoo to wash out wax
and coloring from the hair. Illustrative of its chelating abilities,
citric acid was the first successful <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Eluant" title="Eluant">eluant</a> used for total ion-exchange separation of the <a href="https://en.wikipedia.org/wiki/Lanthanide" title="Lanthanide">lanthanides</a>, during the <a href="https://en.wikipedia.org/wiki/Manhattan_Project" title="Manhattan Project">Manhattan Project</a> in the 1940s. In the 1950s, it was replaced by the far more efficient <a href="https://en.wikipedia.org/wiki/Ethylenediaminetetraacetic_acid" title="Ethylenediaminetetraacetic acid">EDTA</a>.
</p><p>In industry, it is used to dissolve rust from steel, and to <a href="https://en.wikipedia.org/wiki/Passivation_(chemistry)" title="Passivation (chemistry)">passivate</a> <a href="https://en.wikipedia.org/wiki/Stainless_steel" title="Stainless steel">stainless steels</a>.
</p>
<h3><span id="Cosmetics.2C_pharmaceuticals.2C_dietary_supplements.2C_and_foods"></span><span class="mw-headline" id="Cosmetics,_pharmaceuticals,_dietary_supplements,_and_foods">Cosmetics, pharmaceuticals, dietary supplements, and foods</span></h3><p>Citric acid is used as an <a href="https://en.wikipedia.org/wiki/Acidulant" title="Acidulant">acidulant</a>
in creams, gels, and liquids. Used in foods and dietary supplements, it
may be classified as a processing aid if it was added for a technical
or functional effect (e.g. acidulent, chelator, viscosifier, etc.). If
it is still present in insignificant amounts, and the technical or
functional effect is no longer present, it may be exempt from labeling.
</p><p>Citric acid is an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alpha_hydroxy_acid" title="Alpha hydroxy acid">alpha hydroxy acid</a> and is an active ingredient in chemical skin peels.
</p><p>Citric acid is commonly used as a buffer to increase the solubility of brown <a href="https://en.wikipedia.org/wiki/Heroin" title="Heroin">heroin</a>.
</p><p>Citric acid is used as one of the active ingredients in the production of facial tissues with antiviral properties.
</p>
<h3><span class="mw-headline" id="Other_uses">Other uses</span></h3><p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Buffering_agent" title="Buffering agent">buffering</a> properties of citrates are used to control <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> in household cleaners and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pharmaceutical" title="Pharmaceutical">pharmaceuticals</a>.
</p><p>Citric acid is used as an odorless alternative to <a class="mw-redirect" href="https://en.wikipedia.org/wiki/White_vinegar" title="White vinegar">white vinegar</a> for fabric dyeing with <a href="https://en.wikipedia.org/wiki/Acid_dye" title="Acid dye">acid dyes</a>.
</p><p>Sodium citrate is a component of <a href="https://en.wikipedia.org/wiki/Benedict%27s_reagent" title="Benedict's reagent">Benedict's reagent</a>, used for both qualitative and quantitative identification of reducing sugars.
</p><p>Citric acid can be used as an alternative to nitric acid in <a href="https://en.wikipedia.org/wiki/Passivation_(chemistry)" title="Passivation (chemistry)">passivation</a> of <a href="https://en.wikipedia.org/wiki/Stainless_steel" title="Stainless steel">stainless steel</a>.
</p><p>Citric acid can be used as a lower-odor <a href="https://en.wikipedia.org/wiki/Stop_bath" title="Stop bath">stop bath</a> as part of the process for developing <a href="https://en.wikipedia.org/wiki/Photographic_film" title="Photographic film">photographic film</a>. <a href="https://en.wikipedia.org/wiki/Photographic_developer" title="Photographic developer">Photographic developers</a> are alkaline, so a mild acid is used to neutralize and stop their action quickly, but commonly used <a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">acetic acid</a> leaves a strong vinegar odor in the darkroom.
</p><p><a href="https://en.wikipedia.org/wiki/Citric_acid/potassium-sodium_citrate" title="Citric acid/potassium-sodium citrate">Citric acid/potassium-sodium citrate</a> can be used as a blood acid regulator. The citric acid is included to improve palatability
</p><p>Citric acid is an excellent <a href="https://en.wikipedia.org/wiki/Soldering" title="Soldering">soldering</a> <a href="https://en.wikipedia.org/wiki/Flux_(metallurgy)" title="Flux (metallurgy)">flux</a>,
either dry or as a concentrated solution in water. It should be removed
after soldering, especially with fine wires, as it is mildly corrosive.
It dissolves and rinses quickly in hot water.
</p><p><a href="https://en.wikipedia.org/wiki/Alkali_citrate" title="Alkali citrate">Alkali citrate</a>
can be used as an inhibitor of kidney stones by increasing urine
citrate levels, useful for prevention of calcium stones, and increasing
urine pH, useful for preventing uric acid and cystine stones.
</p>
<h2><span class="mw-headline" id="Synthesis_of_other_organic_compounds">Synthesis of other organic compounds</span></h2><p>Citric acid is a versatile precursor to many other organic compounds. Dehydration routes give <a href="https://en.wikipedia.org/wiki/Itaconic_acid" title="Itaconic acid">itaconic acid</a> and its anhydride. <a href="https://en.wikipedia.org/wiki/Citraconic_acid" title="Citraconic acid">Citraconic acid</a> can be produced via thermal isomerization of itaconic acid anhydride. The required itaconic acid anhydride is obtained by dry distillation of citric acid. <a href="https://en.wikipedia.org/wiki/Aconitic_acid" title="Aconitic acid">Aconitic acid</a> can be synthesized by dehydration of citric acid using <a href="https://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid">sulfuric acid</a>:
</p>
<dl><dd>(HO<sub>2</sub>CCH<sub>2</sub>)<sub>2</sub>C(OH)CO<sub>2</sub>H → HO<sub>2</sub>CCH=C(CO<sub>2</sub>H)CH<sub>2</sub>CO<sub>2</sub>H + H<sub>2</sub>O</dd></dl>
<p><a href="https://en.wikipedia.org/wiki/Acetonedicarboxylic_acid" title="Acetonedicarboxylic acid">Acetonedicarboxylic acid</a> can also be prepared by <a href="https://en.wikipedia.org/wiki/Decarboxylation" title="Decarboxylation">decarboxylation</a> of citric acid in fuming sulfuric acid.
</p>
<h2><span class="mw-headline" id="Safety">Safety</span></h2>Although a
weak acid, exposure to pure citric acid can cause adverse effects.
Inhalation may cause cough, shortness of breath, or sore throat.
Over-ingestion may cause abdominal pain and sore throat. Exposure of
concentrated solutions to skin and eyes can cause redness and pain. Long-term or repeated consumption may cause erosion of <a href="https://en.wikipedia.org/wiki/Tooth_enamel" title="Tooth enamel">tooth enamel</a>.David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-36145266480426640762024-03-16T12:50:00.003-04:002024-03-16T12:51:48.439-04:00pH<div class="vector-column-end">
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<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
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<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><a href="https://en.wikipedia.org/wiki/PH">https://en.wikipedia.org/wiki/PH</a><br /><figure class="mw-default-size mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:PH_scale_3.jpg"><img class="mw-file-element" data-file-height="3024" data-file-width="4032" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bd/PH_scale_3.jpg/220px-PH_scale_3.jpg" width="400" /></a><figcaption>Test tubes containing solutions of pH 1–10 colored with <a href="https://en.wikipedia.org/wiki/Universal_indicator" title="Universal indicator">an indicator</a></figcaption></figure>
<p>In <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, <b>pH</b> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="https://en.wikipedia.org/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom: 1px dotted;"><span title="'p' in 'pie'">p</span><span title="/iː/: 'ee' in 'fleece'">iː</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="/eɪ/: 'a' in 'face'">eɪ</span><span title="/tʃ/: 'ch' in 'China'">tʃ</span></span>/</a></span></span> <a href="https://en.wikipedia.org/wiki/Help:Pronunciation_respelling_key" title="Help:Pronunciation respelling key"><i title="English pronunciation respelling">pee-<span style="font-size: 90%;">AYCH</span></i></a>), also referred to as <i>acidity</i> or <i>basicity</i>, historically denotes "<a href="https://en.wikipedia.org/wiki/Electric_potential" title="Electric potential">potential</a> of <a href="https://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">hydrogen</a>" (or "power of hydrogen"). It is a <a href="https://en.wikipedia.org/wiki/Logarithmic_scale" title="Logarithmic scale">logarithmic scale</a> used to specify the <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acidity</a> or <a href="https://en.wikipedia.org/wiki/Base_(chemistry)" title="Base (chemistry)">basicity</a> of <a href="https://en.wikipedia.org/wiki/Aqueous_solution" title="Aqueous solution">aqueous solutions</a>. Acidic solutions (solutions with higher concentrations of hydrogen (<a href="https://en.wikipedia.org/wiki/Hydrogen_ion#Cation_(positively_charged)" title="Hydrogen ion"><span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span></a>) <a href="https://en.wikipedia.org/wiki/Ion" title="Ion">ions</a>) are measured to have lower pH values than basic or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alkaline" title="Alkaline">alkaline</a> solutions.
</p><p>The pH scale is logarithmic and inversely indicates the <a href="https://en.wikipedia.org/wiki/Thermodynamic_activity" title="Thermodynamic activity">activity</a> of <a href="https://en.wikipedia.org/wiki/Hydronium" title="Hydronium">hydrogen ions</a> in the solution
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>pH</mtext>
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<mo>=</mo>
<mo>−</mo>
<mi>log</mi>
<mo></mo>
<mo stretchy="false">(</mo>
<msub>
<mi>a</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>≈</mo>
<mo>−</mo>
<mi>log</mi>
<mo></mo>
<mo stretchy="false">(</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {pH}}=-\log(a_{{\ce {H+}}})\thickapprox -\log([{\ce {H+}}])}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5cee635c4839a5a266cfa10c541a8c7e21d2707e" style="height: 3.009ex; vertical-align: -0.838ex; width: 31.63ex;" /></span></dd></dl>
<p>where [H<sup>+</sup>] is the <a href="https://en.wikipedia.org/wiki/Equilibrium_chemistry" title="Equilibrium chemistry">equilibrium</a> <a href="https://en.wikipedia.org/wiki/Molar_concentration" title="Molar concentration">molar concentration</a> (mol/L) of H<sup>+</sup> in the solution. At 25 <a href="https://en.wikipedia.org/wiki/Celsius" title="Celsius">°C</a> (77<a href="https://en.wikipedia.org/wiki/Fahrenheit" title="Fahrenheit">°F</a>), solutions with a pH less than 7 are acidic, and solutions with a pH greater than 7 are basic. Solutions with a pH of 7 at 25 <a href="https://en.wikipedia.org/wiki/Celsius" title="Celsius">°C</a> are neutral (i.e. have the same concentration of H<sup>+</sup> ions as OH<sup>−</sup> ions, i.e. the same as <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pure_water" title="Pure water">pure water</a>).
The neutral value of the pH depends on the temperature and is lower
than 7 if the temperature increases above 25 °C. The pH range is
commonly given as zero to 14, but a pH value can be less than 0 for very
concentrated <a href="https://en.wikipedia.org/wiki/Acid_strength" title="Acid strength">strong acids</a> or greater than 14 for very concentrated <a href="https://en.wikipedia.org/wiki/Base_(chemistry)#Strong_bases" title="Base (chemistry)">strong bases</a>.
</p><p>The pH scale is <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Measurement_traceability" title="Measurement traceability">traceable</a> to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a <a href="https://en.wikipedia.org/wiki/Galvanic_cell" title="Galvanic cell">concentration cell with transference</a> by measuring the potential difference between a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydrogen_electrode" title="Hydrogen electrode">hydrogen electrode</a> and a <a href="https://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)" title="Standard electrode potential (data page)">standard electrode</a> such as the <a href="https://en.wikipedia.org/wiki/Silver_chloride_electrode" title="Silver chloride electrode">silver chloride electrode</a>. The pH of aqueous solutions can be measured with a <a href="https://en.wikipedia.org/wiki/Glass_electrode" title="Glass electrode">glass electrode</a> and a <a href="https://en.wikipedia.org/wiki/PH_meter" title="PH meter">pH meter</a> or a color-changing <a href="https://en.wikipedia.org/wiki/PH_indicator" title="PH indicator">indicator</a>. Measurements of pH are important in <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, <a href="https://en.wikipedia.org/wiki/Agronomy" title="Agronomy">agronomy</a>, medicine, water treatment, and many other applications.
</p>
<h2><span class="mw-headline" id="History">History</span></h2></div></div></div><p>
In 1909, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Danish_people" title="Danish people">Danish</a> chemist <a class="mw-redirect" href="https://en.wikipedia.org/wiki/S%C3%B8ren_Peder_Lauritz_S%C3%B8rensen" title="Søren Peder Lauritz Sørensen">Søren Peter Lauritz Sørensen</a> introduced the concept of pH at the <a href="https://en.wikipedia.org/wiki/Carlsberg_Laboratory" title="Carlsberg Laboratory">Carlsberg Laboratory</a>, originally using the notation "p<sub>H•</sub>",
with H• as a subscript to the lowercase p. The concept was later
revised in 1924 to the modern pH to accommodate definitions and
measurements in terms of electrochemical cells.</p><blockquote><p>For the sign <i>p</i>, I propose the name 'hydrogen ion exponent' and the symbol p<sub>H•</sub>. Then, for the hydrogen ion exponent (p<sub>H•</sub>) of a solution, the negative value of the <a href="https://en.wikipedia.org/wiki/Common_logarithm" title="Common logarithm">Briggsian logarithm</a> of the related hydrogen ion <a href="https://en.wikipedia.org/wiki/Equivalent_concentration" title="Equivalent concentration">normality factor</a> is to be understood.</p></blockquote><p>Sørensen did not explain why he used the letter p, and the exact meaning of the letter is still disputed. Sørensen described a way of measuring pH using <i>potential</i> differences, and it represents the negative <i>power</i> of 10 in the concentration of hydrogen ions. The letter <i>p</i> could stand for the French <i>puissance,</i> German <i>Potenz,</i> or Danish <i>potens</i>, all meaning "power", or it could mean "potential". All of these words start with the letter <i>p</i> in <a href="https://en.wikipedia.org/wiki/French_language" title="French language">French</a>, <a href="https://en.wikipedia.org/wiki/German_language" title="German language">German</a>, and <a href="https://en.wikipedia.org/wiki/Danish_language" title="Danish language">Danish</a>,
which were the languages in which Sørensen published: Carlsberg
Laboratory was French-speaking; German was the dominant language of
scientific publishing; Sørensen was Danish. He also used the letter <i>q</i>
in much the same way elsewhere in the paper, and he might have
arbitrarily labelled the test solution "p" and the reference solution
"q"; these letters are often paired. Some literature sources suggest that "pH" stands for the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Latin_language" title="Latin language">Latin term</a> <i>pondus hydrogenii</i> (quantity of hydrogen) or <i>potentia hydrogenii</i> (power of hydrogen), although this is not supported by Sørensen's writings. In modern <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, the p stands for "the negative <a href="https://en.wikipedia.org/wiki/Common_logarithm" title="Common logarithm">decimal logarithm of</a>", and is used in the term p<i>K</i><sub>a</sub> for <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant" title="Acid dissociation constant">acid dissociation constants</a>, so pH is "the negative <a href="https://en.wikipedia.org/wiki/Common_logarithm" title="Common logarithm">decimal logarithm of</a> H<sup>+</sup> ion concentration", while pOH is "the negative decimal logarithm of OH- ion concentration".
</p><p>
Bacteriologist <a href="https://en.wikipedia.org/wiki/Alice_Catherine_Evans" title="Alice Catherine Evans">Alice Catherine Evans</a>, who influenced <a href="https://en.wikipedia.org/wiki/Dairy" title="Dairy">dairying</a> and <a href="https://en.wikipedia.org/wiki/Food_safety" title="Food safety">food safety</a>, credited <a href="https://en.wikipedia.org/wiki/William_Mansfield_Clark" title="William Mansfield Clark">William Mansfield Clark</a>
and colleagues, including herself, with developing pH measuring methods
in the 1910s, which had a wide influence on laboratory and industrial
use thereafter. In her memoir, she does not mention how much, or how
little, Clark and colleagues knew about Sørensen's work a few years
prior. She said:</p><blockquote><p>In
these studies [of bacterial metabolism] Dr. Clark's attention was
directed to the effect of acid on the growth of bacteria. He found that
it is the intensity of the acid in terms of hydrogen-ion concentration
that affects their growth. But existing methods of measuring acidity
determined the quantity, not the intensity, of the acid. Next, with his
collaborators, Dr. Clark developed accurate methods for measuring
hydrogen-ion concentration. These methods replaced the inaccurate
titration method of determining the acid content in use in biologic
laboratories throughout the world. Also they were found to be applicable
in many industrial and other processes in which they came into wide
usage.</p></blockquote><p>The first <a href="https://en.wikipedia.org/wiki/Electronics" title="Electronics">electronic</a> method for measuring pH was invented by <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arnold_Orville_Beckman" title="Arnold Orville Beckman">Arnold Orville Beckman</a>, a professor at the <a href="https://en.wikipedia.org/wiki/California_Institute_of_Technology" title="California Institute of Technology">California Institute of Technology</a> in 1934. It was in response to a request from the local citrus grower <a href="https://en.wikipedia.org/wiki/Sunkist_Growers,_Incorporated" title="Sunkist Growers, Incorporated">Sunkist</a>, which wanted a better method for quickly testing the pH of lemons they were picking from their nearby orchards.
</p><h2><span class="mw-headline" id="Definition">Definition</span></h2><h3><span class="mw-headline" id="pH">pH</span></h3><p>The pH of a solution is defined as the decimal <a href="https://en.wikipedia.org/wiki/Logarithm" title="Logarithm">logarithm</a> of the reciprocal of the <a href="https://en.wikipedia.org/wiki/Hydrogen_ion" title="Hydrogen ion">hydrogen ion</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_(chemistry)" title="Activity (chemistry)">activity</a>, <i>a</i><sub>H</sub>+. Mathematically, pH is expressed as:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>pH</mtext>
</mrow>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mo stretchy="false">(</mo>
<msub>
<mi>a</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>a</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {pH}}=-\log _{10}(a_{{\ce {H+}}})=\log _{10}\left({\frac {1}{a_{{\ce {H+}}}}}\right)}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/932bace628e5b8db56e6220cc82210336491b3ab" style="height: 6.176ex; vertical-align: -2.505ex; width: 34.984ex;" /></span></dd></dl>
<p>For example, for a solution with a hydrogen ion activity of 5×10<sup>−6</sup> (i.e., the concentration of hydrogen ions in <a href="https://en.wikipedia.org/wiki/Mole_(unit)" title="Mole (unit)">moles</a> per litre), the pH of the solution can be calculated as follows:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>pH</mtext>
</mrow>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mo stretchy="false">(</mo>
<mn>5</mn>
<mo>×</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>6</mn>
</mrow>
</msup>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mn>5.3</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {pH}}=-\log _{10}(5\times 10^{-6})=5.3}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1cf76a8ab825684516143408b22f4c3f8435fa8d" style="height: 3.176ex; vertical-align: -0.838ex; width: 29.717ex;" /></span></dd></dl>
<p>The concept of pH was developed because <a href="https://en.wikipedia.org/wiki/Ion-selective_electrode" title="Ion-selective electrode">ion-selective electrodes</a>, which are used to measure pH, respond to activity. The electrode potential, <i>E</i>, follows the <a href="https://en.wikipedia.org/wiki/Nernst_equation" title="Nernst equation">Nernst equation</a> for the hydrogen ion, which can be expressed as:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>E</mi>
<mo>=</mo>
<msup>
<mi>E</mi>
<mrow>
<mn>0</mn>
</mrow>
</msup>
<mo>+</mo>
<mrow>
<mfrac>
<mrow>
<mi>R</mi>
<mi>T</mi>
</mrow>
<mi>F</mi>
</mfrac>
</mrow>
<mi>ln</mi>
<mo></mo>
<mo stretchy="false">(</mo>
<msub>
<mi>a</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>=</mo>
<msup>
<mi>E</mi>
<mrow>
<mn>0</mn>
</mrow>
</msup>
<mo>−</mo>
<mrow>
<mfrac>
<mrow>
<mn>2.303</mn>
<mi>R</mi>
<mi>T</mi>
</mrow>
<mi>F</mi>
</mfrac>
</mrow>
<mrow>
<mtext>pH</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle E=E^{0}+{\frac {RT}{F}}\ln(a_{{\ce {H+}}})=E^{0}-{\frac {2.303RT}{F}}{\ce {pH}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/eaa82a0c1f04198c3b4917b2cf5615b0026ff3fb" style="height: 5.176ex; vertical-align: -1.838ex; width: 44.187ex;" /></span></dd></dl>
<p>where <i>E</i> is a measured potential, <i>E</i><sup>0</sup> is the standard electrode potential, <i>R</i> is the <a href="https://en.wikipedia.org/wiki/Gas_constant" title="Gas constant">gas constant</a>, <i>T</i> is the temperature in <a href="https://en.wikipedia.org/wiki/Kelvin" title="Kelvin">Kelvin</a>, <i>F</i> is the <a href="https://en.wikipedia.org/wiki/Faraday_constant" title="Faraday constant">Faraday constant</a>. For <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>,
the number of electrons transferred is one. The electrode potential is
proportional to pH when pH is defined in terms of activity.
</p><p>The precise measurement of pH is presented in International Standard <a href="https://en.wikipedia.org/wiki/ISO_31-8" title="ISO 31-8">ISO 31-8</a> as follows: A <a href="https://en.wikipedia.org/wiki/Galvanic_cell" title="Galvanic cell">galvanic cell</a> is set up to measure the <a href="https://en.wikipedia.org/wiki/Electromotive_force" title="Electromotive force">electromotive force</a>
(e.m.f.) between a reference electrode and an electrode sensitive to
the hydrogen ion activity when they are both immersed in the same
aqueous solution. The reference electrode may be a <a href="https://en.wikipedia.org/wiki/Silver_chloride_electrode" title="Silver chloride electrode">silver chloride electrode</a> or a <a href="https://en.wikipedia.org/wiki/Saturated_calomel_electrode" title="Saturated calomel electrode">calomel electrode</a>, and the hydrogen-ion selective electrode is a <a href="https://en.wikipedia.org/wiki/Standard_hydrogen_electrode" title="Standard hydrogen electrode">standard hydrogen electrode</a>.
</p>
<dl><dd><span class="texhtml">Reference electrode | concentrated solution of KCl || test solution | H<sub>2</sub> | Pt</span></dd></dl>
<p>Firstly, the cell is filled with a solution of known hydrogen ion activity and the electromotive force, <i>E</i><sub>S</sub>, is measured. Then the electromotive force, <i>E</i><sub>X</sub>, of the same cell containing the solution of unknown pH is measured.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>pH</mtext>
<mrow>
<mo stretchy="false">(</mo>
<mtext>X</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>=</mo>
<mrow>
<mtext>pH</mtext>
<mrow>
<mo stretchy="false">(</mo>
<mtext>S</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>+</mo>
<mrow>
<mfrac>
<mrow>
<msub>
<mi>E</mi>
<mrow>
<mrow>
<mtext>S</mtext>
</mrow>
</mrow>
</msub>
<mo>−</mo>
<msub>
<mi>E</mi>
<mrow>
<mrow>
<mtext>X</mtext>
</mrow>
</mrow>
</msub>
</mrow>
<mi>z</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {pH(X)}}={\ce {pH(S)}}+{\frac {E_{{\ce {S}}}-E_{{\ce {X}}}}{z}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/61d7f14649cf22c1e0a8f70a165821e5367fa721" style="height: 5.343ex; vertical-align: -1.838ex; width: 28.382ex;" /></span></dd></dl>
<p>The difference between the two measured electromotive force values is
proportional to pH. This method of calibration avoids the need to know
the <a href="https://en.wikipedia.org/wiki/Standard_electrode_potential" title="Standard electrode potential">standard electrode potential</a>. The proportionality constant, 1/<i>z</i>, is ideally equal to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<mn>1</mn>
<mrow>
<mn>2.303</mn>
<mi>R</mi>
<mi>T</mi>
<mrow>
<mo>/</mo>
</mrow>
<mi>F</mi>
</mrow>
</mfrac>
</mrow>
<mtext> </mtext>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {1}{2.303RT/F}}\ }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/601de58f17f7415035e83849cbe38e7d0901742f" style="height: 6.009ex; vertical-align: -2.671ex; width: 13.017ex;" /></span>, the "Nernstian slope".
</p><p>In practice, a <a href="https://en.wikipedia.org/wiki/Glass_electrode" title="Glass electrode">glass electrode</a>
is used instead of the cumbersome hydrogen electrode. A combined glass
electrode has an in-built reference electrode. It is calibrated against <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">Buffer solutions</a> of known hydrogen ion (<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>) activity proposed by the International Union of Pure and Applied Chemistry (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/IUPAC" title="IUPAC">IUPAC</a>).
Two or more buffer solutions are used in order to accommodate the fact
that the "slope" may differ slightly from ideal. To calibrate the
electrode, it is first immersed in a standard solution, and the reading
on a <a href="https://en.wikipedia.org/wiki/PH_meter" title="PH meter">pH meter</a>
is adjusted to be equal to the standard buffer's value. The reading
from a second standard buffer solution is then adjusted using the
"slope" control to be equal to the pH for that solution. Further
details, are given in the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/IUPAC" title="IUPAC">IUPAC</a> recommendations.
When more than two buffer solutions are used the electrode is
calibrated by fitting observed pH values to a straight line with respect
to standard buffer values. Commercial standard buffer solutions usually
come with information on the value at 25 °C and a correction factor to
be applied for other temperatures.
</p><p>The pH scale is logarithmic and therefore pH is a <a href="https://en.wikipedia.org/wiki/Dimensionless_quantity" title="Dimensionless quantity">dimensionless quantity</a>.
</p>
<h3><span id="p.5BH.5D"></span><span class="mw-headline" id="p[H]">p[H]</span></h3><p>This was the original definition of Sørensen in 1909, which was superseded in favor of pH in 1924. [H] is the concentration of hydrogen ions, denoted [<span class="chemf nowrap">H<sup>+</sup></span>] in modern chemistry. More correctly, the <a href="https://en.wikipedia.org/wiki/Thermodynamic_activity" title="Thermodynamic activity">thermodynamic activity</a> of <span class="chemf nowrap">H<sup>+</sup></span> in dilute solution should be replaced by [<span class="chemf nowrap">H<sup>+</sup></span>]/c<sub>0</sub>, where the standard state concentration c<sub>0</sub> = 1 mol/L. This ratio is a pure number whose logarithm can be defined.
</p><p>It is possible to measure the concentration of hydrogen ions
directly using an electrode calibrated in terms of hydrogen ion
concentrations. One common method is to <a href="https://en.wikipedia.org/wiki/Titration" title="Titration">titrate</a>
a solution of known concentration of a strong acid with a solution of
known concentration of strong base in the presence of a relatively high
concentration of background electrolyte. By knowing the concentrations
of the acid and base, the concentration of hydrogen ions can be
calculated and the measured potential can be correlated with
concentrations. The calibration is usually carried out using a <a href="https://en.wikipedia.org/wiki/Gran_plot#Electrode_calibration" title="Gran plot">Gran plot</a>. This procedure makes the activity of hydrogen ions equal to the numerical value of concentration.
</p><p>The glass electrode (and other <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ion_selective_electrode" title="Ion selective electrode">Ion selective electrodes</a>)
should be calibrated in a medium similar to the one being investigated.
For instance, if one wishes to measure the pH of a seawater sample, the
electrode should be calibrated in a solution resembling seawater in its
chemical composition.
</p><p>The difference between p[H] and pH is quite small, and it has been stated that pH = p[H] + 0.04. However, it is common practice to use the term "pH" for both types of measurement.
</p>
<h3><span class="mw-headline" id="pOH">pOH</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:PHscalenolang.svg"><img class="mw-file-element" data-file-height="205" data-file-width="731" height="113" src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/PHscalenolang.svg/220px-PHscalenolang.svg.png" width="400" /></a><figcaption>Relation between pH and pOH. Red represents the acidic region. Blue represents the basic region.</figcaption></figure>
<p>pOH is sometimes used as a measure of the concentration of hydroxide ions, <span class="chemf nowrap">OH<sup class="template-chem2-sup">−</sup></span>.
pOH values are derived from pH measurements. The concentration of
hydroxide ions in water is related to the concentration of hydrogen ions
by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo>=</mo>
<mrow>
<mfrac>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>W</mtext>
</mrow>
</mrow>
</msub>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {OH^-}}]={\frac {K_{{\ce {W}}}}{[{\ce {H^+}}]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0e914d2d8665e01b649b6ecc09acdb2bb823b33c" style="height: 6.343ex; vertical-align: -2.838ex; width: 14.838ex;" /></span></dd></dl>
<p>where <i>K</i><sub>W</sub> is the <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">self-ionization</a> constant of water. Taking <a href="https://en.wikipedia.org/wiki/Logarithm" title="Logarithm">Logarithms</a>,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>pOH</mtext>
</mrow>
<mo>=</mo>
<mrow>
<mtext>p</mtext>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>W</mtext>
</mrow>
</mrow>
</msub>
<mo>−</mo>
<mrow>
<mtext>pH</mtext>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {pOH}}={\ce {p}}K_{{\ce {W}}}-{\ce {pH}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/759d32a09b7693aeef989fecebaa74adce9da236" style="height: 2.509ex; vertical-align: -0.671ex; width: 19.652ex;" /></span></dd></dl>
<p>So, at room temperature, pOH ≈ 14 − pH. However this relationship is
not strictly valid in other circumstances, such as in measurements of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Alkaline_soils" title="Alkaline soils">soil alkalinity</a>.
</p>
<h2><span class="mw-headline" id="Measurement">Measurement</span></h2><h3><span class="mw-headline" id="pH_Indicators">pH Indicators</span></h3><table class="wikitable floatright">
<tbody><tr>
<th colspan="3">Average pH of common solutions
</th></tr>
<tr>
<th>Substance
</th>
<th>pH range
</th>
<th>Type
</th></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Sulfuric_acid" title="Sulfuric acid">Battery acid</a>
</td>
<td style="background-color: #cc0000; color: white; text-align: center;">< 1
</td>
<td rowspan="6" style="text-align: center;"><a href="https://en.wikipedia.org/wiki/Acid" title="Acid">Acid</a>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Gastric_acid" title="Gastric acid">Gastric acid</a>
</td>
<td style="background-color: #ee0000; color: white; text-align: center;">1.0 – 1.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Orange_juice" title="Orange juice">Orange juice</a>
</td>
<td style="background-color: #ff6600; text-align: center;">3.3 – 4.2
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Vinegar" title="Vinegar">Vinegar</a>
</td>
<td style="background-color: #ff9900; text-align: center;">4-5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Coffee" title="Coffee">Black coffee</a>
</td>
<td style="background-color: yellow; text-align: center;">5 – 5.03
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Milk" title="Milk">Milk</a>
</td>
<td style="background-color: #99cc33; text-align: center;">6.5 – 6.8
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Pure_water" title="Pure water">Pure water</a> at 25 °C
</td>
<td style="background-color: #339933; color: white; text-align: center;">7
</td>
<td style="text-align: center;">Neutral
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Sea_water" title="Sea water">Sea water</a>
</td>
<td style="background-color: #19cdff; color: black; text-align: center;">7.5 – 8.4
</td>
<td rowspan="4" style="text-align: center;"><a href="https://en.wikipedia.org/wiki/Base_(chemistry)" title="Base (chemistry)">Base</a>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Ammonia" title="Ammonia">Ammonia</a>
</td>
<td style="background-color: #3333ff; color: white; text-align: center;">11.0 – 11.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Bleach" title="Bleach">Bleach</a>
</td>
<td style="background-color: #330099; color: white; text-align: center;">12.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Lye" title="Lye">1 M NaOH</a>
</td>
<td style="background-color: #330066; color: white; text-align: center;">14
</td></tr></tbody></table>
<div class="hatnote navigation-not-searchable" role="note"> </div><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/PH_indicator" title="PH indicator">pH indicator</a></div>
<p>pH can be measured using indicators, which change color depending on
the pH of the solution they are in. By comparing the color of a test
solution to a standard color chart, the pH can be estimated to the
nearest whole number. For more precise measurements, the color can be
measured using a <a href="https://en.wikipedia.org/wiki/Colorimeter_(chemistry)" title="Colorimeter (chemistry)">colorimeter</a> or <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Spectrophotometer" title="Spectrophotometer">spectrophotometer</a>. A <a href="https://en.wikipedia.org/wiki/Universal_indicator" title="Universal indicator">Universal indicator</a>
is a mixture of several indicators that can provide a continuous color
change over a range of pH values, typically from about pH 2 to pH 10.
Universal indicator paper is made from absorbent paper that has been
impregnated with universal indicator. An alternative method of
measuring pH is using an electronic <a href="https://en.wikipedia.org/wiki/PH_meter" title="PH meter">pH meter</a>, which directly measures the voltage difference between a pH-sensitive electrode and a reference electrode.
</p>
<h3><span class="mw-headline" id="Non-aqueous_solutions">Non-aqueous solutions</span></h3><p>pH values can be measured in non-aqueous solutions, but they are based on a different scale from aqueous pH values, because the <a href="https://en.wikipedia.org/wiki/Standard_state" title="Standard state">standard states</a> used for calculating hydrogen ion concentrations (<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_(chemistry)" title="Activity (chemistry)">activities</a>) are different. The hydrogen ion activity, <i>a<sub>H<sup>+</sup></sub></i>, is defined as:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>a</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mi>exp</mi>
<mo></mo>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<msub>
<mi>μ</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mo>−</mo>
<msubsup>
<mi>μ</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
<mrow>
<mo>⊖</mo>
</mrow>
</msubsup>
</mrow>
<mrow>
<mi>R</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle a_{{\ce {H+}}}=\exp \left({\frac {\mu _{{\ce {H+}}}-\mu _{{\ce {H+}}}^{\ominus }}{RT}}\right)}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c2554db9edcefbf9fbe64b965caf52d88fbef11c" style="height: 7.509ex; vertical-align: -3.171ex; width: 26.043ex;" /></span></dd></dl>
<p>where <i>μ</i><sub>H<sup>+</sup></sub> is the <a href="https://en.wikipedia.org/wiki/Chemical_potential" title="Chemical potential">chemical potential</a> of the hydrogen ion, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msubsup>
<mi>μ</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
<mrow>
<mo>⊖</mo>
</mrow>
</msubsup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mu _{{\ce {H+}}}^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4b94d142b00deab67cbdaa710bcd956bb12cc916" style="height: 3.509ex; vertical-align: -1.338ex; width: 4.069ex;" /></span> is its chemical potential in the chosen standard state, <i>R</i> is the <a href="https://en.wikipedia.org/wiki/Gas_constant" title="Gas constant">gas constant</a> and <i>T</i> is the <a href="https://en.wikipedia.org/wiki/Thermodynamic_temperature" title="Thermodynamic temperature">thermodynamic temperature</a>.
Therefore, pH values on the different scales cannot be compared
directly because of differences in the solvated proton ions, such as
lyonium ions, which require an intersolvent scale which involves the
transfer activity coefficient of <a href="https://en.wikipedia.org/wiki/Lyonium_ion" title="Lyonium ion">hydronium/lyonium ion</a>.
</p><p>pH is an example of an <a href="https://en.wikipedia.org/wiki/Acidity_function" title="Acidity function">acidity function</a>, but there are others that can be defined. For example, the <a href="https://en.wikipedia.org/wiki/Hammett_acidity_function" title="Hammett acidity function">Hammett acidity function</a>, <i>H</i><sub>0</sub>, has been developed in connection with <a href="https://en.wikipedia.org/wiki/Superacid" title="Superacid">Superacids</a>.
</p>
<h3><span class="mw-headline" id="Unified_absolute_pH_scale">Unified absolute pH scale</span></h3><p>In
2010, a new approach to measuring pH was proposed, called the "unified
absolute pH scale". This approach allows for a common reference standard
to be used across different solutions, regardless of their pH range.
The unified absolute pH scale is based on the absolute chemical
potential of the proton, as defined by the <a href="https://en.wikipedia.org/wiki/Lewis_acids_and_bases" title="Lewis acids and bases">Lewis acid–base</a> theory. This scale is applicable to liquids, gases, and even solids.
The advantages of the unified absolute pH scale include consistency,
accuracy, and applicability to a wide range of sample types. It is
precise and versatile because it serves as a common reference standard
for pH measurements. However, implementation efforts, compatibility with
existing data, complexity, and potential costs are some challenges.
</p>
<h3><span class="mw-headline" id="Extremes_of_pH_measurements">Extremes of pH measurements</span></h3><p>The measurement of pH can become difficult at extremely acidic or alkaline conditions, such as below pH 2.5 (ca. 0.003 <a href="https://en.wikipedia.org/wiki/Mole_(unit)" title="Mole (unit)">mol</a>/dm<sup>3</sup> acid) or above pH 10.5 (above ca. 0.0003 mol/dm<sup>3</sup> alkaline). This is due to the breakdown of the <a href="https://en.wikipedia.org/wiki/Nernst_equation" title="Nernst equation">Nernst equation</a> in such conditions when using a glass electrode. There are several factors that contribute to this problem. Firstly, <a href="https://en.wikipedia.org/wiki/Liquid_junction_potential" title="Liquid junction potential">liquid junction potentials</a> may not be independent of pH. Secondly, the high <a href="https://en.wikipedia.org/wiki/Ionic_strength" title="Ionic strength">ionic strength</a>
of concentrated solutions can affect the electrode potentials. At high
pH the glass electrode may be affected by "alkaline error", because the
electrode becomes sensitive to the concentration of cations such as <span class="chemf nowrap">Na<sup class="template-chem2-sup">+</sup></span> and <span class="chemf nowrap">K<sup class="template-chem2-sup">+</sup></span> in the solution. To overcome these problems, specially constructed electrodes are available.
</p><p>Runoff from mines or mine tailings can produce some extremely low pH values.
</p>
<h2><span class="mw-headline" id="Applications">Applications</span></h2><p>Pure water has a pH of 7 at 25°C, meaning it is neutral. When an <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acid</a> is dissolved in water, the pH will be less than 7, while a <a href="https://en.wikipedia.org/wiki/Base_(chemistry)" title="Base (chemistry)">base</a>, or <a href="https://en.wikipedia.org/wiki/Alkali" title="Alkali">alkali</a>, will have a pH greater than 7. A strong acid, such as <a href="https://en.wikipedia.org/wiki/Hydrochloric_acid" title="Hydrochloric acid">hydrochloric acid</a>, at concentration 1 mol dm<sup>−3</sup> has a pH of 0, while a strong alkali like <a href="https://en.wikipedia.org/wiki/Sodium_hydroxide" title="Sodium hydroxide">sodium hydroxide</a>,
at the same concentration, has a pH of 14. Since pH is a logarithmic
scale, a difference of one in pH is equivalent to a tenfold difference
in hydrogen ion concentration.
</p><p>Neutrality is not exactly 7 at 25°C, but 7 serves as a good
approximation in most cases. Neutrality occurs when the concentration of
hydrogen ions ([<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]) equals the concentration of hydroxide ions ([<span class="chemf nowrap">OH<sup class="template-chem2-sup">−</sup></span>]), or when their activities are equal. Since <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">self-ionization of water</a> holds the product of these concentration [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>] × [<span class="chemf nowrap">OH<sup class="template-chem2-sup">−</sup></span>] = K<sub>w</sub>, it can be seen that at neutrality [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>] = [<span class="chemf nowrap">OH<sup class="template-chem2-sup">−</sup></span>] = <span class="nowrap">√<span style="border-top: 1px solid; padding: 0px 0.1em;">K<sub>w</sub></span></span>, or pH = pK<sub>w</sub>/2. pK<sub>w</sub>
is approximately 14 but depends on ionic strength and temperature, and
so the pH of neutrality does also. Pure water and a solution of <a href="https://en.wikipedia.org/wiki/Sodium_chloride" title="Sodium chloride">NaCl</a> in pure water are both neutral, since <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">dissociation of water</a>
produces equal numbers of both ions. However the pH of the neutral NaCl
solution will be slightly different from that of neutral pure water
because the hydrogen and hydroxide ions' activity is dependent on <a href="https://en.wikipedia.org/wiki/Ionic_strength" title="Ionic strength">ionic strength</a>, so K<sub>w</sub> varies with ionic strength.
</p><p>When pure water is exposed to air, it becomes mildly acidic. This is because water absorbs <a href="https://en.wikipedia.org/wiki/Carbon_dioxide" title="Carbon dioxide">carbon dioxide</a> from the air, which is then slowly converted into <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate</a> and hydrogen ions (essentially creating <a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">carbonic acid</a>).
</p>
<dl><dd><span class="chemf nowrap">CO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span>+ H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span>O ⇌ HCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span>+ H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: 0.8em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">+</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;"></sub></span></span></dd></dl>
<h3><span class="mw-headline" id="pH_in_soil">pH in soil</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Soil_pH" title="Soil pH">Soil pH</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Soil_pH_effect_on_nutrient_availability.svg"><img class="mw-file-element" data-file-height="448" data-file-width="512" height="351" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Soil_pH_effect_on_nutrient_availability.svg/220px-Soil_pH_effect_on_nutrient_availability.svg.png" width="400" /></a><figcaption>Nutritional elements availability within soil varies with pH. Light blue color represents the ideal range for most plants.</figcaption></figure>
<p>The United States Department of Agriculture <a href="https://en.wikipedia.org/wiki/Natural_Resources_Conservation_Service" title="Natural Resources Conservation Service">Natural Resources Conservation Service</a>, formerly Soil Conservation Service classifies <a href="https://en.wikipedia.org/wiki/Soil_pH" title="Soil pH">soil pH</a> ranges as follows:
</p>
<table class="wikitable" style="align: center;">
<tbody><tr>
<th scope="col">Denomination
</th>
<th scope="col">pH range
</th></tr>
<tr>
<td>Ultra acidic
</td>
<td>< 3.5
</td></tr>
<tr>
<td>Extremely acidic
</td>
<td>3.5–4.4
</td></tr>
<tr>
<td>Very strongly acidic
</td>
<td>4.5–5.0
</td></tr>
<tr>
<td>Strongly acidic
</td>
<td>5.1–5.5
</td></tr>
<tr>
<td>Moderately acidic
</td>
<td>5.6–6.0
</td></tr>
<tr>
<td>Slightly acidic
</td>
<td>6.1–6.5
</td></tr>
<tr>
<td>Neutral
</td>
<td>6.6–7.3
</td></tr>
<tr>
<td>Slightly alkaline
</td>
<td>7.4–7.8
</td></tr>
<tr>
<td>Moderately alkaline
</td>
<td>7.9–8.4
</td></tr>
<tr>
<td>Strongly alkaline
</td>
<td>8.5–9.0
</td></tr>
<tr>
<td>Very strongly alkaline
</td>
<td>9.0–10.5
</td></tr>
<tr>
<td>Hyper alkaline
</td>
<td>> 10.5
</td></tr></tbody></table>
<p>In Europe, topsoil pH is influenced by soil parent material, erosional effects, climate and vegetation. A recent map
of topsoil pH in Europe shows the alkaline soils in Mediterranean,
Hungary, East Romania, North France. Scandinavian countries, Portugal,
Poland and North Germany have more acid soils.
</p>
<h3><span class="mw-headline" id="pH_in_plants">pH in plants</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Lemon_-_whole_and_split.jpg"><img class="mw-file-element" data-file-height="4000" data-file-width="6000" height="267" src="https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Lemon_-_whole_and_split.jpg/220px-Lemon_-_whole_and_split.jpg" width="400" /></a><figcaption><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lemon_juice" title="Lemon juice">Lemon juice</a> tastes sour because it contains 5% to 6% <a href="https://en.wikipedia.org/wiki/Citric_acid" title="Citric acid">citric acid</a> and has a pH of 2.2 (high acidity).</figcaption></figure>
<p>Plants contain pH-dependent <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Plant_pigment" title="Plant pigment">pigments</a> that can be used as <a href="https://en.wikipedia.org/wiki/PH_indicator" title="PH indicator">pH indicators</a>, such as those found in <a href="https://en.wikipedia.org/wiki/Hibiscus" title="Hibiscus">hibiscus</a>, <a href="https://en.wikipedia.org/wiki/Red_cabbage" title="Red cabbage">red cabbage</a> (<a href="https://en.wikipedia.org/wiki/Anthocyanin" title="Anthocyanin">anthocyanin</a>), and grapes (<a href="https://en.wikipedia.org/wiki/Red_wine" title="Red wine">red wine</a>). <a href="https://en.wikipedia.org/wiki/Citrus" title="Citrus">Citrus</a> fruits have acidic juice primarily due to the presence of <a href="https://en.wikipedia.org/wiki/Citric_acid" title="Citric acid">citric acid</a>, while other <a href="https://en.wikipedia.org/wiki/Carboxylic_acid" title="Carboxylic acid">carboxylic acids</a> can be found in various living systems. The <a href="https://en.wikipedia.org/wiki/Protonation" title="Protonation">protonation</a> state of <a href="https://en.wikipedia.org/wiki/Phosphate" title="Phosphate">phosphate</a> derivatives, including <a href="https://en.wikipedia.org/wiki/Adenosine_triphosphate" title="Adenosine triphosphate">ATP</a>, is pH-dependent. <a href="https://en.wikipedia.org/wiki/Hemoglobin" title="Hemoglobin">Hemoglobin</a>, an oxygen-transport enzyme, is also affected by pH in a phenomenon known as the <a href="https://en.wikipedia.org/wiki/Root_effect" title="Root effect">Root effect</a>.
</p>
<h3><span class="mw-headline" id="pH_in_the_ocean">pH in the ocean</span></h3><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Seawater#pH_value" title="Seawater">Seawater § pH value</a>, <a href="https://en.wikipedia.org/wiki/Ocean#pH_and_alkalinity" title="Ocean">Ocean § pH and alkalinity</a>, and <a href="https://en.wikipedia.org/wiki/Ocean_acidification" title="Ocean acidification">Ocean acidification</a></div>
<p>The pH of <a href="https://en.wikipedia.org/wiki/Seawater" title="Seawater">seawater</a> plays an important role in the ocean's <a href="https://en.wikipedia.org/wiki/Carbon_cycle#Ocean" title="Carbon cycle">carbon cycle</a>. There is evidence of ongoing <a href="https://en.wikipedia.org/wiki/Ocean_acidification" title="Ocean acidification">ocean acidification</a> (meaning a drop in pH value): Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Carbon_dioxide_emissions" title="Carbon dioxide emissions">Carbon dioxide emissions</a> from human activities are the primary cause of ocean acidification, with <a href="https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphere" title="Carbon dioxide in Earth's atmosphere">atmospheric carbon dioxide (CO<sub>2</sub>) levels</a> exceeding 410 ppm (in 2020). CO<sub>2</sub> from the <a href="https://en.wikipedia.org/wiki/Atmosphere" title="Atmosphere">atmosphere</a> is absorbed by the oceans. This produces <a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">carbonic acid</a> (H<sub>2</sub>CO<sub>3</sub>) which dissociates into a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bicarbonate_ion" title="Bicarbonate ion">bicarbonate ion</a> (<span class="chemf nowrap">HCO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">3</sub></span></span>) and a <a href="https://en.wikipedia.org/wiki/Hydrogen_ion" title="Hydrogen ion">hydrogen ion</a> (H<sup>+</sup>). The presence of free hydrogen ions (H<sup>+</sup>) lowers the pH of the ocean.
</p>
<h4><span class="mw-headline" id="Three_pH_scales_in_oceanography">Three pH scales in oceanography</span></h4><p>The measurement of pH in seawater is complicated by the <a href="https://en.wikipedia.org/wiki/Chemical_property" title="Chemical property">chemical properties</a> of seawater, and three distinct pH scales exist in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chemical_oceanography" title="Chemical oceanography">chemical oceanography</a>.
In practical terms, the three seawater pH scales differ in their pH
values up to 0.10, differences that are much larger than the accuracy of
pH measurements typically required, in particular, in relation to the
ocean's <a href="https://en.wikipedia.org/wiki/Total_inorganic_carbon" title="Total inorganic carbon">carbonate system</a>. Since it omits consideration of sulfate and fluoride ions, the <i>free scale</i>
is significantly different from both the total and seawater scales.
Because of the relative unimportance of the fluoride ion, the total and
seawater scales differ only very slightly.
</p><p>As part of its <a href="https://en.wikipedia.org/wiki/Operational_definition" title="Operational definition">operational definition</a> of the pH scale, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/IUPAC" title="IUPAC">IUPAC</a> defines a series of <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">Buffer solutions</a> across a range of pH values (often denoted with <a class="mw-redirect" href="https://en.wikipedia.org/wiki/National_Bureau_of_Standards" title="National Bureau of Standards">National Bureau of Standards</a> (NBS) or <a href="https://en.wikipedia.org/wiki/National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a> (NIST) designation). These solutions have a relatively low <a href="https://en.wikipedia.org/wiki/Ionic_strength" title="Ionic strength">ionic strength</a>
(≈0.1) compared to that of seawater (≈0.7), and, as a consequence, are
not recommended for use in characterizing the pH of seawater, since the
ionic strength differences cause changes in <a href="https://en.wikipedia.org/wiki/Standard_electrode_potential" title="Standard electrode potential">electrode potential</a>. To resolve this problem, an alternative series of buffers based on <a href="https://en.wikipedia.org/wiki/Artificial_seawater" title="Artificial seawater">artificial seawater</a> was developed.
This new series resolves the problem of ionic strength differences
between samples and the buffers, and the new pH scale is referred to as
the <i>total scale</i>, often denoted as <i>pH<sub>T</sub></i>. The total scale was defined using a medium containing <a href="https://en.wikipedia.org/wiki/Sulfate" title="Sulfate">sulfate</a> ions. These ions experience <a href="https://en.wikipedia.org/wiki/Protonation" title="Protonation">protonation</a>, <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> + <span class="chemf nowrap">SO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span>↔ HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>, such that the total scale includes the effect of both <a href="https://en.wikipedia.org/wiki/Proton" title="Proton">protons</a> (free hydrogen ions) and hydrogen sulfate ions:
</p>
<dl><dd>[<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>T</sub> = [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> + [<span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>]</dd></dl>
<p>An alternative scale, the <i>free scale</i>, often denoted <i>pH<sub>F</sub></i>, omits this consideration and focuses solely on [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub>, in principle making it a simpler representation of hydrogen ion concentration. Only [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>T</sub> can be determined, therefore [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> must be estimated using the [<span class="chemf nowrap">SO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>] and the stability constant of <span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>, <span class="nowrap">K<span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">*</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">S</sub></span></span>:
</p>
<dl><dd>[<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> = [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>T</sub> − [<span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>] = [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>T</sub> ( 1 + [<span class="chemf nowrap">SO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>] / K<span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">*</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">S</sub></span> )<sup>−1</sup></dd></dl>
<p>However, it is difficult to estimate K<span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">*</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">S</sub></span> in seawater, limiting the utility of the otherwise more straightforward free scale.
</p><p>Another scale, known as the <i>seawater scale</i>, often denoted <i>pH<sub>SWS</sub></i>, takes account of a further protonation relationship between hydrogen ions and <a href="https://en.wikipedia.org/wiki/Fluoride" title="Fluoride">fluoride</a> ions, <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> + <span class="chemf nowrap">F<sup class="template-chem2-sup">−</sup></span> ⇌ HF. Resulting in the following expression for [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>SWS</sub>:
</p>
<dl><dd>[<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>SWS</sub> = [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> + [<span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>] + [HF]</dd></dl>
<p>However, the advantage of considering this additional complexity is
dependent upon the abundance of fluoride in the medium. In seawater, for
instance, sulfate ions occur at much greater concentrations (>400
times) than those of fluoride. As a consequence, for most practical
purposes, the difference between the total and seawater scales is very
small.
</p><p>The following three equations summarize the three scales of pH:
</p>
<dl><dd>pH<sub>F</sub> = −log [<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub></dd><dd>pH<sub>T</sub> = −log([<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> + [<span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>]) = −log[<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>T</sub></dd><dd>pH<sub>SWS</sub> = −log(<span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>]<sub>F</sub> + [<span class="chemf nowrap">HSO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span>] + [HF]) = −log[v]<sub>SWS</sub></dd></dl>
<h3><span class="mw-headline" id="pH_of_various_body_fluids">pH of various body fluids</span></h3><dl><dd><table class="wikitable">
<caption>pH of various body fluids
</caption>
<tbody><tr>
<th>Compartment
</th>
<th>pH
</th></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Gastric_acid" title="Gastric acid">Gastric acid</a></td>
<td>1.5–3.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Lysosome" title="Lysosome">Lysosomes</a></td>
<td>4.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Human_skin" title="Human skin">Human skin</a></td>
<td>4.7
</td></tr>
<tr>
<td>Granules of <a href="https://en.wikipedia.org/wiki/Chromaffin_cell" title="Chromaffin cell">chromaffin cells</a></td>
<td>5.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Urine" title="Urine">Urine</a></td>
<td>6.0
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Cytosol" title="Cytosol">Cytosol</a></td>
<td>7.2
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Blood" title="Blood">Blood</a> (natural pH)</td>
<td>7.34–7.45
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Cerebrospinal_fluid" title="Cerebrospinal fluid">Cerebrospinal fluid</a> (CSF)</td>
<td>7.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Mitochondrial_matrix" title="Mitochondrial matrix">Mitochondrial matrix</a></td>
<td>7.5
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Pancreas" title="Pancreas">Pancreas</a> secretions</td>
<td>8.1
</td></tr></tbody></table></dd></dl>
<p>In living organisms, the pH of various <a href="https://en.wikipedia.org/wiki/Body_fluid" title="Body fluid">Body fluids</a>, cellular compartments, and organs is tightly regulated to maintain a state of acid-base balance known as <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis" title="Acid–base homeostasis">acid–base homeostasis</a>. <a href="https://en.wikipedia.org/wiki/Acidosis" title="Acidosis">Acidosis</a>,
defined by blood pH below 7.35, is the most common disorder of
acid–base homeostasis and occurs when there is an excess of acid in the
body. In contrast, <a href="https://en.wikipedia.org/wiki/Alkalosis" title="Alkalosis">alkalosis</a> is characterized by excessively high blood pH.
</p><p>Blood pH is usually slightly basic, with a pH of 7.365, referred to as physiological pH in biology and medicine. <a href="https://en.wikipedia.org/wiki/Dental_plaque" title="Dental plaque">Plaque</a> formation in teeth can create a local acidic environment that results in <a href="https://en.wikipedia.org/wiki/Tooth_decay" title="Tooth decay">tooth decay</a> through demineralization. <a href="https://en.wikipedia.org/wiki/Enzyme" title="Enzyme">Enzymes</a> and other <a href="https://en.wikipedia.org/wiki/Protein" title="Protein">Proteins</a> have an optimal pH range for function and can become inactivated or <a href="https://en.wikipedia.org/wiki/Denaturation_(biochemistry)" title="Denaturation (biochemistry)">denatured</a> outside this range.
</p>
<h2><span class="mw-headline" id="pH_calculations">pH calculations</span></h2><p>When calculating the pH of a solution containing acids and/or bases, a <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants#Speciation_calculations" title="Determination of equilibrium constants">chemical speciation calculation</a>
is used to determine the concentration of all chemical species present
in the solution. The complexity of the procedure depends on the nature
of the solution. Strong acids and bases are compounds that are almost
completely dissociated in water, which simplifies the calculation.
However, for weak acids, a <a href="https://en.wikipedia.org/wiki/Quadratic_equation" title="Quadratic equation">quadratic equation</a> must be solved, and for weak bases, a cubic equation is required. In general, a set of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Non-linear" title="Non-linear">non-linear</a> <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Simultaneous_equation" title="Simultaneous equation">simultaneous equations</a> must be solved.
</p><p>Water itself is a weak acid and a weak base, so its dissociation
must be taken into account at high pH and low solute concentration (see <a href="https://en.wikipedia.org/wiki/Amphoterism" title="Amphoterism">amphoterism</a>). It <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">dissociates</a> according to the equilibrium
</p>
<dl><dd><span class="chemf nowrap">2 H<sub class="template-chem2-sub">2</sub>O ⇌ H<sub class="template-chem2-sub">3</sub>O<sup class="template-chem2-sup">+</sup> (aq) + OH<sup class="template-chem2-sup">−</sup> (aq)</span></dd></dl>
<p>with a <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant" title="Acid dissociation constant">dissociation constant</a>, <i><span class="texhtml mvar" style="font-style: italic;">K<sub>w</sub></span></i> defined as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mi>w</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{w}={\ce {[H+][OH^{-}]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4bbddc96ecfaf0a74d351c6ce2c7de2eb8c01688" style="height: 3.009ex; vertical-align: -0.838ex; width: 17.384ex;" /></span></dd></dl>
<p>where [H<sup>+</sup>] stands for the concentration of the aqueous <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydronium_ion" title="Hydronium ion">hydronium ion</a> and [OH<sup>−</sup>] represents the concentration of the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydroxide_ion" title="Hydroxide ion">hydroxide ion</a>. This equilibrium needs to be taken into account at high pH and when the solute concentration is extremely low.
</p>
<h3><span class="mw-headline" id="Strong_acids_and_bases">Strong acids and bases</span></h3><p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Strong_acid" title="Strong acid">Strong acids</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Strong_base" title="Strong base">bases</a>
are compounds that are essentially fully dissociated in water. This
means that in an acidic solution, the concentration of hydrogen ions
(H+) can be considered equal to the concentration of the acid.
Similarly, in a basic solution, the concentration of hydroxide ions
(OH-) can be considered equal to the concentration of the base. The pH
of a solution is defined as the negative logarithm of the concentration
of H+, and the pOH is defined as the negative logarithm of the
concentration of OH-. For example, the pH of a 0.01M solution of
hydrochloric acid (HCl) is equal to 2 (pH = −log10(0.01)), while the pOH
of a 0.01M solution of sodium hydroxide (NaOH) is equal to 2 (pOH =
−log10(0.01)), which corresponds to a pH of about 12.
</p><p>However, self-ionization of water must also be considered when
concentrations of a strong acid or base is very low or high. For
instance, a 5×10<sup>−8</sup>M solution of HCl would be expected to have
a pH of 7.3 based on the above procedure, which is incorrect as it is
acidic and should have a pH of less than 7. In such cases, the system
can be treated as a mixture of the acid or base and water, which is an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Amphoteric" title="Amphoteric">amphoteric</a> substance. By accounting for the self-ionization of water, the true pH of the solution can be calculated. For example, a 5×10<sup>−8</sup>M
solution of HCl would have a pH of 6.89 when treated as a mixture of
HCl and water. The self-ionization equilibrium of solutions of sodium
hydroxide at higher concentrations must also be considered.
</p>
<h3><span class="mw-headline" id="Weak_acids_and_bases">Weak acids and bases</span></h3><p>A <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Weak_acid" title="Weak acid">weak acid</a> or the conjugate acid of a weak base can be treated using the same formalism.
</p>
<ul><li>Acid HA: <span class="chemf nowrap">HA ⇌ H<sup class="template-chem2-sup">+</sup> + A<sup class="template-chem2-sup">−</sup></span></li><li>Base A: <span class="chemf nowrap">HA<sup class="template-chem2-sup">+</sup> ⇌ H<sup class="template-chem2-sup">+</sup> + A</span></li></ul>
<p>First, an acid dissociation constant is defined as follows.
Electrical charges are omitted from subsequent equations for the sake of
generality
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>H</mtext>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>A</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{a}={\frac {{\ce {[H] [A]}}}{{\ce {[HA]}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f29a403e204523dcc5d4345e9da4125d6bccc8e0" style="height: 6.509ex; vertical-align: -2.671ex; width: 13.083ex;" /></span></dd></dl>
<p>and its value is assumed to have been determined by experiment. This being so, there are three unknown concentrations, [HA], [H<sup>+</sup>] and [A<sup>−</sup>] to determine by calculation. Two additional equations are needed. One way to provide them is to apply the law of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Mass_conservation" title="Mass conservation">mass conservation</a> in terms of the two "reagents" H and A.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow>
<mrow>
<mtext>A</mtext>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>A</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mo>+</mo>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle C_{{\ce {A}}}={\ce {[A]}}+{\ce {[HA]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9ebde93fda69a21943e8842a9a32da905b2f645e" style="height: 2.843ex; vertical-align: -0.838ex; width: 16.882ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow>
<mrow>
<mtext>H</mtext>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>H</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mo>+</mo>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle C_{{\ce {H}}}={\ce {[H]}}+{\ce {[HA]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/920b90697a63b1c14c8302e733fc525ba0d9585b" style="height: 2.843ex; vertical-align: -0.838ex; width: 16.882ex;" /></span></dd></dl>
<p>C stands for <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Analytical_concentration" title="Analytical concentration">analytical concentration</a>.
In some texts, one mass balance equation is replaced by an equation of
charge balance. This is satisfactory for simple cases like this one, but
is more difficult to apply to more complicated cases as those below.
Together with the equation defining K<sub>a</sub>, there are now three equations in three unknowns. When an acid is dissolved in water C<sub>A</sub> = C<sub>H</sub> = C<sub>a</sub>,
the concentration of the acid, so [A] = [H]. After some further
algebraic manipulation an equation in the hydrogen ion concentration may
be obtained.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mn>2</mn>
</mrow>
</msup>
<mo>+</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>−</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<msub>
<mi>C</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo>=</mo>
<mn>0</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {H}}]^{2}+K_{a}[{\ce {H}}]-K_{a}C_{a}=0}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/46348613cafd9be4dcf2b772575b5af47f080d54" style="height: 3.176ex; vertical-align: -0.838ex; width: 25.983ex;" /></span></dd></dl>
<p>Solution of this <a href="https://en.wikipedia.org/wiki/Quadratic_equation" title="Quadratic equation">quadratic equation</a> gives the hydrogen ion concentration and hence p[H] or, more loosely, pH. This procedure is illustrated in an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/ICE_table" title="ICE table">ICE table</a>
which can also be used to calculate the pH when some additional
(strong) acid or alkaline has been added to the system, that is, when C<sub>A</sub> ≠ C<sub>H</sub>.
</p><p>For example, what is the pH of a 0.01M solution of <a href="https://en.wikipedia.org/wiki/Benzoic_acid" title="Benzoic acid">benzoic acid</a>, pK<sub>a</sub> = 4.19?
</p>
<ul><li>Step 1: <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
<mo>=</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>4.19</mn>
</mrow>
</msup>
<mo>=</mo>
<mn>6.46</mn>
<mo>×</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>5</mn>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{a}=10^{-4.19}=6.46\times 10^{-5}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8ba5721f63f313ffed3e2d4f1c4c0470276b2445" style="height: 3.009ex; vertical-align: -0.671ex; width: 27.663ex;" /></span></li><li>Step 2: Set up the quadratic equation. <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mn>2</mn>
</mrow>
</msup>
<mo>+</mo>
<mn>6.46</mn>
<mo>×</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>5</mn>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>−</mo>
<mn>6.46</mn>
<mo>×</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>7</mn>
</mrow>
</msup>
<mo>=</mo>
<mn>0</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {H}}]^{2}+6.46\times 10^{-5}[{\ce {H}}]-6.46\times 10^{-7}=0}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3b00dbc68e7860d66750e413f778916b6b915cd9" style="height: 3.176ex; vertical-align: -0.838ex; width: 40.334ex;" /></span></li><li>Step 3: Solve the quadratic equation. <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo>=</mo>
<mn>7.74</mn>
<mo>×</mo>
<msup>
<mn>10</mn>
<mrow>
<mo>−</mo>
<mn>4</mn>
</mrow>
</msup>
<mo>;</mo>
<mspace width="1em"></mspace>
<mrow>
<mi mathvariant="normal">p</mi>
<mi mathvariant="normal">H</mi>
</mrow>
<mo>=</mo>
<mn>3.11</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {H+}}]=7.74\times 10^{-4};\quad \mathrm {pH} =3.11}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d23e6dd79b1f843749965771698d8a5403a236a4" style="height: 3.176ex; vertical-align: -0.838ex; width: 32.903ex;" /></span></li></ul>
<p>For alkaline solutions, an additional term is added to the
mass-balance equation for hydrogen. Since the addition of hydroxide
reduces the hydrogen ion concentration, and the hydroxide ion
concentration is constrained by the self-ionization equilibrium to be
equal to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<msub>
<mi>K</mi>
<mrow>
<mi>w</mi>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {K_{w}}{{\ce {[H+]}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/671c1d10d6bce20ed4de57be093835a6aad5019f" style="height: 6.176ex; vertical-align: -2.838ex; width: 5.384ex;" /></span>, the resulting equation is:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow>
<mtext>H</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>+</mo>
<mo stretchy="false">[</mo>
<mrow>
<mtext>HA</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>−</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>w</mi>
</mrow>
</msub>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>H</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle C_{\ce {H}}={\frac {[{\ce {H}}]+[{\ce {HA}}]-K_{w}}{\ce {[H]}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e4eaeb404231cb0a9a118cd2972dc991b67adaab" style="height: 6.509ex; vertical-align: -2.671ex; width: 23.941ex;" /></span></dd></dl>
<h3><span class="mw-headline" id="General_method">General method</span></h3><p>Some systems, such as with <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Polyprotic" title="Polyprotic">polyprotic</a> acids, are amenable to spreadsheet calculations. With three or more reagents or when many complexes are formed with general formulae such as A<sub>p</sub>B<sub>q</sub>H<sub>r</sub>,
the following general method can be used to calculate the pH of a
solution. For example, with three reagents, each equilibrium is
characterized by an equilibrium constant, β.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<msub>
<mrow>
<mtext>A</mtext>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<msub>
<mrow>
<mtext>B</mtext>
</mrow>
<mrow>
<mi>q</mi>
</mrow>
</msub>
<msub>
<mrow>
<mtext>H</mtext>
</mrow>
<mrow>
<mi>r</mi>
</mrow>
</msub>
<mo stretchy="false">]</mo>
<mo>=</mo>
<msub>
<mi>β</mi>
<mrow>
<mi>p</mi>
<mi>q</mi>
<mi>r</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>A</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>p</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>q</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>r</mi>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {A}}_{p}{\ce {B}}_{q}{\ce {H}}_{r}]=\beta _{pqr}[{\ce {A}}]^{p}[{\ce {B}}]^{q}[{\ce {H}}]^{r}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0116cc100cbe49e89c845e94bfb7cfa9d41efdf4" style="height: 3.009ex; vertical-align: -1.005ex; width: 28.452ex;" /></span></dd></dl>
<p>Next, write down the mass-balance equations for each reagent:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtable columnalign="right left right left right left right left right left right left" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true" rowspacing="3pt">
<mtr>
<mtd>
<msub>
<mi>C</mi>
<mrow>
<mtext>A</mtext>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mo stretchy="false">[</mo>
<mrow>
<mtext>A</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>+</mo>
<mi mathvariant="normal">Σ</mi>
<mi>p</mi>
<msub>
<mi>β</mi>
<mrow>
<mi>p</mi>
<mi>q</mi>
<mi>r</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>A</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>p</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>q</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>r</mi>
</mrow>
</msup>
</mtd>
</mtr>
<mtr>
<mtd>
<msub>
<mi>C</mi>
<mrow>
<mtext>B</mtext>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>+</mo>
<mi mathvariant="normal">Σ</mi>
<mi>q</mi>
<msub>
<mi>β</mi>
<mrow>
<mi>p</mi>
<mi>q</mi>
<mi>r</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>A</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>p</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>q</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>r</mi>
</mrow>
</msup>
</mtd>
</mtr>
<mtr>
<mtd>
<msub>
<mi>C</mi>
<mrow>
<mtext>H</mtext>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo>+</mo>
<mi mathvariant="normal">Σ</mi>
<mi>r</mi>
<msub>
<mi>β</mi>
<mrow>
<mi>p</mi>
<mi>q</mi>
<mi>r</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>A</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>p</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>q</mi>
</mrow>
</msup>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>r</mi>
</mrow>
</msup>
<mo>−</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>w</mi>
</mrow>
</msub>
<mo stretchy="false">[</mo>
<mrow>
<mtext>H</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mo>−</mo>
<mn>1</mn>
</mrow>
</msup>
</mtd>
</mtr>
</mtable>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\begin{aligned}C_{\ce {A}}&=[{\ce {A}}]+\Sigma p\beta _{pqr}[{\ce {A}}]^{p}[{\ce {B}}]^{q}[{\ce {H}}]^{r}\\C_{\ce {B}}&=[{\ce {B}}]+\Sigma q\beta _{pqr}[{\ce {A}}]^{p}[{\ce {B}}]^{q}[{\ce {H}}]^{r}\\C_{\ce {H}}&=[{\ce {H}}]+\Sigma r\beta _{pqr}[{\ce {A}}]^{p}[{\ce {B}}]^{q}[{\ce {H}}]^{r}-K_{w}[{\ce {H}}]^{-1}\end{aligned}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3d204f0d1baca5254f67602e86ba0091a004b673" style="height: 9.676ex; vertical-align: -4.338ex; width: 43.079ex;" /></span></dd></dl>
<p>Note that there are no approximations involved in these equations,
except that each stability constant is defined as a quotient of
concentrations, not activities. Much more complicated expressions are
required if activities are to be used.
</p><p>There are three <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Simultaneous_equation" title="Simultaneous equation">simultaneous equations</a>
in the three unknowns, [A], [B] and [H]. Because the equations are
non-linear and their concentrations may range over many powers of 10,
the solution of these equations is not straightforward. However, many
computer programs are available which can be used to perform these
calculations. There may be more than three reagents. The calculation of
hydrogen ion concentrations, using this approach, is a key element in
the <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants" title="Determination of equilibrium constants">determination of equilibrium constants</a> by <a href="https://en.wikipedia.org/wiki/Potentiometric_titration" title="Potentiometric titration">potentiometric titration</a>.
</p>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.comtag:blogger.com,1999:blog-3207547956289570927.post-74847254453384076952024-03-16T12:18:00.000-04:002024-03-16T12:18:04.558-04:00Acid dissociation constant<div class="vector-column-end">
<div class="vector-sticky-pinned-container">
</div>
</div>
<div aria-labelledby="firstHeading" class="vector-body ve-init-mw-desktopArticleTarget-targetContainer" data-mw-ve-target-container="" id="bodyContent">
<div class="vector-body-before-content">
<div class="mw-indicators">
</div>
<div class="noprint" id="siteSub">From Wikipedia, the free encyclopedia</div>
</div>
<div id="contentSub"><div id="mw-content-subtitle"></div></div>
<div class="mw-body-content" id="mw-content-text"><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant">https://en.wikipedia.org/wiki/Acid_dissociation_constant</a></div><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"> </div><div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en">In <a href="https://en.wikipedia.org/wiki/Chemistry" title="Chemistry">chemistry</a>, an <b>acid dissociation constant</b> (also known as <b>acidity constant</b>, or <b>acid-ionization constant</b>; denoted <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mi>a</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{a}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6ab146730b53d8924ba153a8459e7b19aeb5f0af" style="height: 2.509ex; vertical-align: -0.671ex; width: 3.075ex;" /></span></span>) is a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Quantitative_property" title="Quantitative property">quantitative</a> measure of the <a href="https://en.wikipedia.org/wiki/Acid_strength" title="Acid strength">strength</a> of an <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acid</a> in <a href="https://en.wikipedia.org/wiki/Solution_(chemistry)" title="Solution (chemistry)">solution</a>. It is the <a href="https://en.wikipedia.org/wiki/Equilibrium_constant" title="Equilibrium constant">equilibrium constant</a> for a <a href="https://en.wikipedia.org/wiki/Chemical_reaction" title="Chemical reaction">chemical reaction</a>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HA</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HA <=> A^- + H^+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9a21e2949f5afc0e8b29a6840889ef9f6121faab" style="height: 2.843ex; vertical-align: -0.505ex; width: 17.482ex;" /></span></dd></dl>
<p>known as <a href="https://en.wikipedia.org/wiki/Dissociation_(chemistry)" title="Dissociation (chemistry)">dissociation</a> in the context of <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction" title="Acid–base reaction">acid–base reactions</a>. The <a href="https://en.wikipedia.org/wiki/Chemical_species" title="Chemical species">chemical species</a> HA is an <a href="https://en.wikipedia.org/wiki/Acid" title="Acid">acid</a> that dissociates into <span class="chemf nowrap">A<sup class="template-chem2-sup">−</sup></span>, the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Conjugate_base" title="Conjugate base">conjugate base</a> of the acid and a <a href="https://en.wikipedia.org/wiki/Hydron_(chemistry)" title="Hydron (chemistry)">hydrogen ion</a>, <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span>. The system is said to be in <a href="https://en.wikipedia.org/wiki/Chemical_equilibrium" title="Chemical equilibrium">equilibrium</a>
when the concentrations of its components will not change over time,
because both forward and backward reactions are occurring at the same
rate.
</p><p>The dissociation constant is defined by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">A</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">H</mi>
<mi mathvariant="normal">A</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{a}}=\mathrm {\frac {[A^{-}][H^{+}]}{[HA]}} ,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7cdd9efda0e3a32060020b5c9e5b2c78981b2a93" style="height: 6.509ex; vertical-align: -2.671ex; width: 16.704ex;" /></span> or</dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>a</mtext>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{{\ce {a}}}=-\log _{10}K_{\text{a}}=\log _{10}{\frac {{\ce {[HA]}}}{[{\ce {A^-}}][{\ce {H+}}]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d7af05bf129db2f9bc618fe809660b6e4ff8dce9" style="height: 6.676ex; vertical-align: -2.838ex; width: 36.141ex;" /></span></dd></dl>
<p>where quantities in square brackets represent the <a href="https://en.wikipedia.org/wiki/Concentration" title="Concentration">concentrations</a> of the species at equilibrium. As a simple example for a weak acid with <i>K</i><sub>a</sub> = 10<sup>−5</sup>, log <i>K</i><sub>a</sub> is the exponent which is -5, so that p<i>K</i><sub>a</sub> = 5. And for acetic acid with <i>K</i><sub>a</sub> = 1.8 x 10<sup>−5</sup>, p<i>K</i><sub>a</sub> is close to 5. A higher <i>K</i><sub>a</sub> corresponds to a stronger acid which is more dissociated at equilibrium. For the more convenient <a href="https://en.wikipedia.org/wiki/Logarithmic_scale" title="Logarithmic scale">logarithmic scale</a>, a lower p<i>K</i><sub>a</sub> means a stronger acid.
</p>
<h2><span class="mw-headline" id="Theoretical_background">Theoretical background</span></h2></div></div></div><p>The acid dissociation constant for an acid is a direct consequence of the underlying <a href="https://en.wikipedia.org/wiki/Chemical_thermodynamics" title="Chemical thermodynamics">thermodynamics</a> of the dissociation reaction; the p<i>K</i><sub>a</sub> value is directly proportional to the standard <a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy">Gibbs free energy</a> change for the reaction. The value of the p<i>K</i><sub>a</sub> changes with temperature and can be understood qualitatively based on <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Le_Ch%C3%A2telier%27s_principle" title="Le Châtelier's principle">Le Châtelier's principle</a>: when the reaction is <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Endothermic" title="Endothermic">endothermic</a>, <i>K</i><sub>a</sub> increases and p<i>K</i><sub>a</sub> decreases with increasing temperature; the opposite is true for <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Exothermic" title="Exothermic">exothermic</a> reactions.
</p><p>The value of p<i>K</i><sub>a</sub> also depends on molecular structure of the acid in many ways. For example, <a href="https://en.wikipedia.org/wiki/Linus_Pauling" title="Linus Pauling">Pauling</a> proposed two rules: one for successive p<i>K</i><sub>a</sub> of polyprotic acids (see <a class="mw-selflink-fragment" href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#Polyprotic_acids">Polyprotic acids</a> below), and one to estimate the p<i>K</i><sub>a</sub> of oxyacids based on the number of =O and −OH groups (see <a class="mw-selflink-fragment" href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#Factors_that_affect_pKa_values">Factors that affect p<i>K</i><sub>a</sub> values</a> below). Other structural factors that influence the magnitude of the acid dissociation constant include <a href="https://en.wikipedia.org/wiki/Inductive_effect" title="Inductive effect">inductive effects</a>, <a href="https://en.wikipedia.org/wiki/Mesomeric_effect" title="Mesomeric effect">mesomeric effects</a>, and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydrogen_bonding" title="Hydrogen bonding">hydrogen bonding</a>. <a href="https://en.wikipedia.org/wiki/Hammett_equation" title="Hammett equation">Hammett type equations</a> have frequently been applied to the estimation of p<i>K</i><sub>a</sub>.
</p><p>The quantitative behaviour of acids and bases in solution can be understood only if their p<i>K</i><sub>a</sub> values are known. In particular, the <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> of a solution can be predicted when the analytical concentration and p<i>K</i><sub>a</sub>
values of all acids and bases are known; conversely, it is possible to
calculate the equilibrium concentration of the acids and bases in
solution when the pH is known. These calculations find application in
many different areas of chemistry, biology, medicine, and geology. For
example, many compounds used for medication are weak acids or bases, and
a knowledge of the p<i>K</i><sub>a</sub> values, together with the <a href="https://en.wikipedia.org/wiki/Octanol-water_partition_coefficient" title="Octanol-water partition coefficient">octanol-water partition coefficient</a>,
can be used for estimating the extent to which the compound enters the
blood stream. Acid dissociation constants are also essential in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Aquatic_chemistry" title="Aquatic chemistry">aquatic chemistry</a> and <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chemical_oceanography" title="Chemical oceanography">chemical oceanography</a>, where the acidity of water plays a fundamental role. In living organisms, <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis" title="Acid–base homeostasis">acid–base homeostasis</a> and <a href="https://en.wikipedia.org/wiki/Enzyme_kinetics" title="Enzyme kinetics">enzyme kinetics</a> are dependent on the p<i>K</i><sub>a</sub> values of the many acids and bases present in the cell and in the body. In chemistry, a knowledge of p<i>K</i><sub>a</sub> values is necessary for the preparation of <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">buffer solutions</a> and is also a prerequisite for a quantitative understanding of the interaction between acids or bases and metal ions to form <a href="https://en.wikipedia.org/wiki/Stability_constants_of_complexes" title="Stability constants of complexes">complexes</a>. Experimentally, p<i>K</i><sub>a</sub> values can be determined by potentiometric (pH) <a href="https://en.wikipedia.org/wiki/Titration" title="Titration">titration</a>, but for values of p<i>K</i><sub>a</sub> less than about 2 or more than about 11, <a href="https://en.wikipedia.org/wiki/Spectrophotometry" title="Spectrophotometry">spectrophotometric</a> or <a href="https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance" title="Nuclear magnetic resonance">NMR</a> measurements may be required due to practical difficulties with pH measurements.
</p>
<h2><span class="mw-headline" id="Definitions">Definitions</span></h2><p>According to <a href="https://en.wikipedia.org/wiki/Svante_Arrhenius" title="Svante Arrhenius">Arrhenius</a>'s <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction#Arrhenius_definition" title="Acid–base reaction">original molecular definition</a>, an acid is a substance that <a href="https://en.wikipedia.org/wiki/Dissociation_(chemistry)" title="Dissociation (chemistry)">dissociates</a> in aqueous solution, releasing the hydrogen ion <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> (a proton):
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HA</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HA <=> A- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/963f015ff617dc95a47e35c5d64c5e1515e72fc1" style="height: 2.843ex; vertical-align: -0.505ex; width: 17.482ex;" /></span></dd></dl>
<p>The equilibrium constant for this dissociation reaction is known as a <a href="https://en.wikipedia.org/wiki/Dissociation_constant" title="Dissociation constant">dissociation constant</a>. The liberated proton combines with a water molecule to give a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydronium_ion" title="Hydronium ion">hydronium (or oxonium) ion</a> <span class="chemf nowrap">H<sub class="template-chem2-sub">3</sub>O<sup class="template-chem2-sup">+</sup></span> (naked protons do not exist in solution), and so Arrhenius later proposed that the dissociation should be written as an <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction" title="Acid–base reaction">acid–base reaction</a>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HA</mtext>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msup>
<mtext>O</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HA + H2O <=> A- + H3O+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f9f929b936fa45ebaf589df959a776126dbda39a" style="height: 3.343ex; vertical-align: -1.005ex; width: 27.791ex;" /></span></dd></dl>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Acetic-acid-dissociation-3D-balls.png"><img alt="Acetic acid, CH3COOH, is composed of a methyl group, CH3, bound chemically to a carboxylate group, COOH. The carboxylate group can lose a proton and donate it to a water molecule, H2O, leaving behind an acetate anion CH3COO− and creating a hydronium cation H3O. This is an equilibrium reaction, so the reverse process can also take place." class="mw-file-element" data-file-height="513" data-file-width="2150" height="96" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/96/Acetic-acid-dissociation-3D-balls.png/330px-Acetic-acid-dissociation-3D-balls.png" width="400" /></a><figcaption><a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">Acetic acid</a>, a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Weak_acid" title="Weak acid">weak acid</a>, donates a proton (hydrogen ion, highlighted in green) to water in an equilibrium reaction to give the <a href="https://en.wikipedia.org/wiki/Acetate" title="Acetate">acetate</a> ion and the <a href="https://en.wikipedia.org/wiki/Hydronium" title="Hydronium">hydronium</a> ion. Red: oxygen, black: carbon, white: hydrogen.</figcaption></figure>
<p><a href="https://en.wikipedia.org/wiki/Br%C3%B8nsted%E2%80%93Lowry_acid%E2%80%93base_theory" title="Brønsted–Lowry acid–base theory">Brønsted and Lowry</a> generalised this further to a proton exchange reaction:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>acid</mtext>
</mrow>
<mo>+</mo>
<mrow>
<mtext>base </mtext>
</mrow>
<mrow>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
</mrow>
<mrow>
<mtext> conjugate base</mtext>
</mrow>
<mo>+</mo>
<mrow>
<mtext>conjugate acid</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\text{acid}}+{\text{base }}{\ce {<=>}}{\text{ conjugate base}}+{\text{conjugate acid}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/990a22f22c6c1ca62978ab86b2d7f8296a038fc8" style="height: 3.009ex; vertical-align: -0.671ex; width: 47.944ex;" /></span></dd></dl>
<p>The acid loses a proton, leaving a conjugate base; the proton is
transferred to the base, creating a conjugate acid. For aqueous
solutions of an acid HA, the base is water; the conjugate base is <span class="chemf nowrap">A<sup class="template-chem2-sup">−</sup></span> and the conjugate acid is the hydronium ion. The Brønsted–Lowry definition applies to other solvents, such as <a href="https://en.wikipedia.org/wiki/Dimethyl_sulfoxide" title="Dimethyl sulfoxide">dimethyl sulfoxide</a>: the solvent S acts as a base, accepting a proton and forming the conjugate acid <span class="chemf nowrap">SH<sup class="template-chem2-sup">+</sup></span>.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HA</mtext>
<mo>+</mo>
<mtext>S</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>SH</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HA + S <=> A- + SH+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b36e9ac02f052610d0e069623d6ca0cef1731343" style="height: 2.843ex; vertical-align: -0.505ex; width: 22.908ex;" /></span></dd></dl>
<p>In solution chemistry, it is common to use <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> as an abbreviation for the solvated hydrogen ion, regardless of the solvent. In aqueous solution <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> denotes a <a href="https://en.wikipedia.org/wiki/Hydronium#Solvation" title="Hydronium">solvated hydronium ion</a> rather than a proton.
</p><p>The designation of an acid or base as "conjugate" depends on the context. The conjugate acid <span class="chemf nowrap">BH<sup class="template-chem2-sup">+</sup></span> of a base B dissociates according to
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msup>
<mtext>BH</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<mtext>B</mtext>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {BH+ + OH- <=> B + H2O}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8fc8af2c412bb12c03d46837a4bbae30c1a60170" style="height: 3.343ex; vertical-align: -1.005ex; width: 26.541ex;" /></span></dd></dl>
<p>which is the reverse of the equilibrium
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
</mrow>
<mrow>
<mtext> (acid)</mtext>
</mrow>
<mo>+</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<mrow>
<mtext> (base) </mtext>
</mrow>
<mrow>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mrow>
<mtext> (conjugate base)</mtext>
</mrow>
<mo>+</mo>
<mrow>
<msup>
<mtext>BH</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mrow>
<mtext> (conjugate acid)</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2O}}{\text{ (acid)}}+{\ce {B}}{\text{ (base) }}{\ce {<=> OH-}}{\text{ (conjugate base)}}+{\ce {BH+}}{\text{ (conjugate acid)}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2550397c64354664b21587d6f23834ed4c3a995f" style="height: 3.343ex; vertical-align: -1.005ex; width: 73.781ex;" /></span></dd></dl>
<p>The <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydroxide_ion" title="Hydroxide ion">hydroxide ion</a> <span class="chemf nowrap">OH<sup class="template-chem2-sup">−</sup></span>,
a well known base, is here acting as the conjugate base of the acid
water. Acids and bases are thus regarded simply as donors and acceptors
of protons respectively.
</p><p>A broader definition of acid dissociation includes <a href="https://en.wikipedia.org/wiki/Hydrolysis" title="Hydrolysis">hydrolysis</a>, in which protons are produced by the splitting of water molecules. For example, <a href="https://en.wikipedia.org/wiki/Boric_acid" title="Boric acid">boric acid</a> (<span class="chemf nowrap">B(OH)<sub class="template-chem2-sub">3</sub></span>) produces <span class="chemf nowrap">H<sub class="template-chem2-sub">3</sub>O<sup class="template-chem2-sup">+</sup></span> as if it were a proton donor, but it has been confirmed by <a href="https://en.wikipedia.org/wiki/Raman_spectroscopy" title="Raman spectroscopy">Raman spectroscopy</a> that this is due to the hydrolysis equilibrium:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>B</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<mtext>OH</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo>+</mo>
<mn>2</mn>
<mspace width="thinmathspace"></mspace>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<mtext>B</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<mtext>OH</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msup>
<mtext>O</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {B(OH)3 + 2 H2O <=> B(OH)4- + H3O+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ed23a610a75938ad6ebe2d6a20a8075ec6e12651" style="height: 3.343ex; vertical-align: -1.005ex; width: 39.177ex;" /></span></dd></dl>
<p>Similarly, <a href="https://en.wikipedia.org/wiki/Hydrolysis#Hydrolysis_of_metal_aqua_ions" title="Hydrolysis">metal ion hydrolysis</a> causes ions such as <span class="chemf nowrap">[Al(H<sub class="template-chem2-sub">2</sub>O)<sub class="template-chem2-sub">6</sub>]<sup>3+</sup></span> to behave as weak acids:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msup>
<mrow>
<mo stretchy="false">[</mo>
<mtext>Al</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>6</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mn>3</mn>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mrow>
<mo stretchy="false">[</mo>
<mtext>Al</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>5</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mo stretchy="false">(</mo>
<mtext>OH</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mn>2</mn>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msup>
<mtext>O</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {[Al(H2O)6]^3+ + H2O <=> [Al(H2O)5(OH)]^2+ + H3O+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b1c60923d504a87f8bbd22293ac8eaad8341ea41" style="height: 3.509ex; vertical-align: -1.005ex; width: 53.382ex;" /></span></dd></dl>
<p>According to <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction#Lewis_definition" title="Acid–base reaction">Lewis</a>'s original definition, an acid is a substance that accepts an <a href="https://en.wikipedia.org/wiki/Electron_pair" title="Electron pair">electron pair</a> to form a <a href="https://en.wikipedia.org/wiki/Coordinate_covalent_bond" title="Coordinate covalent bond">coordinate covalent bond</a>.
</p>
<h2><span class="mw-headline" id="Equilibrium_constant">Equilibrium constant</span></h2><p>An acid dissociation constant is a particular example of an <a href="https://en.wikipedia.org/wiki/Equilibrium_constant" title="Equilibrium constant">equilibrium constant</a>. The dissociation of a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Monoprotic_acid" title="Monoprotic acid">monoprotic acid</a>, HA, in dilute solution can be written as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HA</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HA <=> A- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/963f015ff617dc95a47e35c5d64c5e1515e72fc1" style="height: 2.843ex; vertical-align: -0.505ex; width: 17.482ex;" /></span></dd></dl>
<p>The thermodynamic equilibrium constant <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1f45734886910651b2143da8310f2b6a094327a4" style="height: 2.509ex; vertical-align: -0.338ex; width: 3.605ex;" /></span></span> can be defined by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo fence="false" stretchy="false">{</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo fence="false" stretchy="false">}</mo>
<mo fence="false" stretchy="false">{</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo fence="false" stretchy="false">}</mo>
</mrow>
<mrow>
<mrow>
<mo fence="false" stretchy="false">{</mo>
<mtext>HA</mtext>
<mo fence="false" stretchy="false">}</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K^{\ominus }={\frac {\{{\ce {A^-}}\}\{{\ce {H+}}\}}{{\ce {\{HA\}}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4ffe524bdd09837f4d5e1733e95476fa7f24dc4b" style="height: 6.676ex; vertical-align: -2.671ex; width: 18.697ex;" /></span></dd></dl>
<p>where <span class="texhtml">{X} </span> represents the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_(chemistry)" title="Activity (chemistry)">activity</a>, at equilibrium, of the chemical species X. <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1f45734886910651b2143da8310f2b6a094327a4" style="height: 2.509ex; vertical-align: -0.338ex; width: 3.605ex;" /></span></span> is <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dimensionless" title="Dimensionless">dimensionless</a>
since activity is dimensionless. Activities of the products of
dissociation are placed in the numerator, activities of the reactants
are placed in the denominator. See <a href="https://en.wikipedia.org/wiki/Activity_coefficient" title="Activity coefficient">activity coefficient</a> for a derivation of this expression.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:PK_acetic_acid.png"><img alt="Illustration of the effect of ionic strength on the p K A of an acid. In this figure, the p K A of acetic acid decreases with increasing ionic strength, dropping from 4.8 in pure water (zero ionic strength) and becoming roughly constant at 4.45 for ionic strengths above 1 molar sodium nitrate, N A N O 3." class="mw-file-element" data-file-height="290" data-file-width="326" height="356" src="https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/PK_acetic_acid.png/200px-PK_acetic_acid.png" width="400" /></a><figcaption>Variation of p<i>K</i><sub>a</sub> of acetic acid with ionic strength.</figcaption></figure>
<p>Since activity is the product of <a href="https://en.wikipedia.org/wiki/Concentration" title="Concentration">concentration</a> and <a href="https://en.wikipedia.org/wiki/Activity_coefficient" title="Activity coefficient">activity coefficient</a> (<i>γ</i>) the definition could also be written as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mo>=</mo>
<mrow>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
<mi mathvariant="normal">Γ</mi>
</mrow>
<mo>,</mo>
<mspace width="1em"></mspace>
<mi mathvariant="normal">Γ</mi>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<msub>
<mi>γ</mi>
<mrow>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
<mtext> </mtext>
<msub>
<mi>γ</mi>
<mrow>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mrow>
</msub>
</mrow>
<mrow>
<msub>
<mi>γ</mi>
<mrow>
<mrow>
<mtext>HA</mtext>
</mrow>
</mrow>
</msub>
<mtext> </mtext>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K^{\ominus }={{\frac {[{\ce {A^-}}][{\ce {H+}}]}{{\ce {[HA]}}}}\Gamma },\quad \Gamma ={\frac {\gamma _{{\ce {A^-}}}\ \gamma _{{\ce {H+}}}}{\gamma _{{\ce {HA}}}\ }}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6e9373db7091aeb4f51a26757a677b420f0a8418" style="height: 6.676ex; vertical-align: -2.671ex; width: 35.154ex;" /></span></dd></dl>
<p>where <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<mtext>HA</mtext>
</mrow>
<mo stretchy="false">]</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\text{HA}}]}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3cfe8305c0735d25de8cef20edf09ef5144d700a" style="height: 2.843ex; vertical-align: -0.838ex; width: 4.78ex;" /></span></span> represents the concentration of HA and <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Γ</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Gamma }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4cfde86a3f7ec967af9955d0988592f0693d2b19" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.453ex;" /></span></span> is a quotient of activity coefficients.
</p><p>To avoid the complications involved in using activities, dissociation constants are <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants" title="Determination of equilibrium constants">determined</a>, where possible, in a medium of high <a href="https://en.wikipedia.org/wiki/Ionic_strength" title="Ionic strength">ionic strength</a>, that is, under conditions in which <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Γ</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Gamma }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4cfde86a3f7ec967af9955d0988592f0693d2b19" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.453ex;" /></span></span> can be assumed to be always constant. For example, the medium might be a solution of 0.1 <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Molar_(unit)" title="Molar (unit)">molar</a> (M) <a href="https://en.wikipedia.org/wiki/Sodium_nitrate" title="Sodium nitrate">sodium nitrate</a> or 3 M <a href="https://en.wikipedia.org/wiki/Potassium_perchlorate" title="Potassium perchlorate">potassium perchlorate</a>. With this assumption,
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mi mathvariant="normal">Γ</mi>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">A</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">H</mi>
<mi mathvariant="normal">A</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{a}}={\frac {K^{\ominus }}{\Gamma }}=\mathrm {\frac {[A^{-}][H^{+}]}{[HA]}} }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2a5a59c740de89347ec4c96d982292fc05c64b2f" style="height: 6.509ex; vertical-align: -2.671ex; width: 23.596ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>a</mtext>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<mtext>HA</mtext>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{{\ce {a}}}=-\log _{10}{\frac {[{\ce {A^-}}][{\ce {H^+}}]}{[{\ce {HA}}]}}=\log _{10}{\frac {{\ce {[HA]}}}{[{\ce {A^-}}][{\ce {H+}}]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/bed5fbab82167a42994a6d735931d08b06f1e7a5" style="height: 6.843ex; vertical-align: -2.838ex; width: 43.045ex;" /></span></dd></dl>
<p>is obtained. Note, however, that all published dissociation constant
values refer to the specific ionic medium used in their determination
and that different values are obtained with different conditions, as
shown for <a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">acetic acid</a>
in the illustration above. When published constants refer to an ionic
strength other than the one required for a particular application, they
may be adjusted by means of <a href="https://en.wikipedia.org/wiki/Specific_ion_interaction_theory" title="Specific ion interaction theory">specific ion theory</a> (SIT) and other theories.
</p>
<h3><span class="mw-headline" id="Cumulative_and_stepwise_constants">Cumulative and stepwise constants</span></h3><p>A cumulative equilibrium constant, denoted by <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi>β</mi>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {\beta } ,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c29cbc53774ba4eefbc007e016618c154ad8bc83" style="height: 2.509ex; vertical-align: -0.671ex; width: 1.979ex;" /></span></span> is related to the product of stepwise constants, denoted by <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">K</mi>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {K} .}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d6e1092b5767a06f757cf8d25ef306ba40997d61" style="height: 2.176ex; vertical-align: -0.338ex; width: 2.455ex;" /></span></span> For a dibasic acid the relationship between stepwise and overall constants is as follows
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>A</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<mn>2</mn>
<mspace width="thinmathspace"></mspace>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2A <=> A^2- + 2H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/14a583ebc8ff6cd998ff00246bc3cf93e2071dd0" style="height: 3.343ex; vertical-align: -1.005ex; width: 20.908ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>β</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>A</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mn>2</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \beta _{2}={\frac {{\ce {[H2A]}}}{[{\ce {A^2-}}][{\ce {H+}}]^{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/08598ffd39aa7af9e4d7ca73764ada00fdc0882f" style="height: 6.843ex; vertical-align: -3.005ex; width: 17.276ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>log</mi>
<mo></mo>
<msub>
<mi>β</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>1</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
<mo>+</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \log \beta _{2}=\mathrm {p} K_{{\ce {a1}}}+\mathrm {p} K_{{\ce {a2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af8b34835ac2f0add9fc00bfedded77ea7677997" style="height: 3.009ex; vertical-align: -1.171ex; width: 21.97ex;" /></span></dd></dl>
<p>Note that in the context of metal-ligand complex formation, the
equilibrium constants for the formation of metal complexes are usually
defined as <i>association</i> constants. In that case, the equilibrium
constants for ligand protonation are also defined as association
constants. The numbering of association constants is the reverse of the
numbering of dissociation constants; in this example <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>log</mi>
<mo></mo>
<msub>
<mi>β</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \log \beta _{1}=\mathrm {p} K_{{\ce {a2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0b640984ed379efc9f11524f18bae782fd7e0098" style="height: 3.009ex; vertical-align: -1.171ex; width: 13.979ex;" /></span>
</p>
<h3><span class="mw-headline" id="Association_and_dissociation_constants">Association and dissociation constants</span></h3><p>When discussing the properties of acids it is usual to specify equilibrium constants as acid dissociation constants, denoted by <i>K</i><sub>a</sub>, with numerical values given the symbol p<i>K</i><sub>a</sub>.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>dissoc</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
<mo>:</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>dissoc</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{dissoc}}={\frac {{\ce {[A- ][H+]}}}{{\ce {[HA]}}}}:\mathrm {p} K_{\text{a}}=-\log K_{\text{dissoc}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c115ab88c5f847b2fe5c3250d9e5c9134d125080" style="height: 6.676ex; vertical-align: -2.671ex; width: 40.788ex;" /></span></dd></dl>
<p>On the other hand, association constants are used for bases.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>assoc</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<mtext>HA</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{assoc}}={\frac {{\ce {[HA]}}}{{\ce {[A- ][H+]}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e353beeaa76919ab646b6969e6d30f7e01fe7afa" style="height: 6.676ex; vertical-align: -2.838ex; width: 18.905ex;" /></span></dd></dl>
<p>However, <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants#Implementations" title="Determination of equilibrium constants">general purpose computer programs</a>
that are used to derive equilibrium constant values from experimental
data use association constants for both acids and bases. Because
stability constants for a <a href="https://en.wikipedia.org/wiki/Coordination_complex" title="Coordination complex">metal-ligand complex</a> are always specified as association constants, ligand protonation must also be specified as an association reaction.
The definitions show that the value of an acid dissociation constant is
the reciprocal of the value of the corresponding association constant:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>dissoc</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mn>1</mn>
<msub>
<mi>K</mi>
<mrow>
<mtext>assoc</mtext>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{dissoc}}={\frac {1}{K_{\text{assoc}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5487fe153f4f3af1329ef5fe54f4a4b0d6aa8d11" style="height: 5.676ex; vertical-align: -2.338ex; width: 16.234ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>dissoc</mtext>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>assoc</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \log K_{\text{dissoc}}=-\log K_{\text{assoc}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3d8e0cd7c13f7612376f5575d2999ed3c322b16c" style="height: 2.509ex; vertical-align: -0.671ex; width: 24.311ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>dissoc</mtext>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>assoc</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{\text{dissoc}}=-\mathrm {p} K_{\text{assoc}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5050a0800a53eaadb4c1f454e14ab84265fa25ea" style="height: 2.509ex; vertical-align: -0.671ex; width: 19.791ex;" /></span></dd></dl>
<p>Notes
</p>
<ol><li>For a given acid or base in water, <span class="nowrap">p<i>K</i><sub>a</sub> + p<i>K</i><sub>b</sub> = p<i>K</i><sub>w</sub></span>, the <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">self-ionization constant of water</a>.</li><li>The association constant for the formation of a <a href="https://en.wikipedia.org/wiki/Supramolecular_chemistry" title="Supramolecular chemistry">supramolecular</a> complex may be denoted as K<sub>a</sub>; in such cases "a" stands for "association", not "acid".</li><li>For polyprotic acids, the numbering of stepwise association
constants is the reverse of the numbering of the dissociation constants.
For example, for <a href="https://en.wikipedia.org/wiki/Phosphoric_acid" title="Phosphoric acid">phosphoric acid</a> (details in the <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#polyprotic_acids">polyprotic acids</a> section below):</li></ol>
<dl><dd><dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtable columnalign="right left right left right left right left right left right left" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true" rowspacing="3pt">
<mtr>
<mtd>
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>assoc</mtext>
</mrow>
<mo>,</mo>
<mn>1</mn>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>dissoc</mtext>
</mrow>
<mo>,</mo>
<mn>3</mn>
</mrow>
</msub>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>assoc</mtext>
</mrow>
<mo>,</mo>
<mn>2</mn>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>dissoc</mtext>
</mrow>
<mo>,</mo>
<mn>2</mn>
</mrow>
</msub>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>log</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>assoc</mtext>
</mrow>
<mo>,</mo>
<mn>3</mn>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>dissoc</mtext>
</mrow>
<mo>,</mo>
<mn>1</mn>
</mrow>
</msub>
</mtd>
</mtr>
</mtable>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\begin{aligned}\log K_{{\text{assoc}},1}&=\mathrm {p} K_{{\text{dissoc}},3}\\\log K_{{\text{assoc}},2}&=\mathrm {p} K_{{\text{dissoc}},2}\\\log K_{{\text{assoc}},3}&=\mathrm {p} K_{{\text{dissoc}},1}\end{aligned}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4bfab8ad3585d45e9830b3a5ae9a4bd06a51de8d" style="height: 9.509ex; vertical-align: -4.171ex; width: 23.36ex;" /></span></dd></dl></dd></dl>
<h3><span class="mw-headline" id="Temperature_dependence">Temperature dependence</span></h3><p>All equilibrium constants vary with <a href="https://en.wikipedia.org/wiki/Temperature" title="Temperature">temperature</a> according to the <a href="https://en.wikipedia.org/wiki/Van_%27t_Hoff_equation" title="Van 't Hoff equation">van 't Hoff equation</a>
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<mrow>
<mrow>
<mi mathvariant="normal">d</mi>
</mrow>
<mi>ln</mi>
<mo></mo>
<mrow>
<mo>(</mo>
<mi>K</mi>
<mo>)</mo>
</mrow>
</mrow>
<mrow>
<mrow>
<mi mathvariant="normal">d</mi>
</mrow>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>H</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mrow>
<mrow>
<mi>R</mi>
<msup>
<mi>T</mi>
<mrow>
<mn>2</mn>
</mrow>
</msup>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {\mathrm {d} \ln \left(K\right)}{\mathrm {d} T}}={\frac {\Delta H^{\ominus }}{RT^{2}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/126632879ea7bd51ed51a800d19ca4f769a87133" style="height: 6.009ex; vertical-align: -2.171ex; width: 17.815ex;" /></span></dd></dl>
<p><span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle R}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4b0bfb3769bf24d80e15374dc37b0441e2616e33" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.764ex;" /></span></span> is the <a href="https://en.wikipedia.org/wiki/Gas_constant" title="Gas constant">gas constant</a> and <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>T</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle T}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ec7200acd984a1d3a3d7dc455e262fbe54f7f6e0" style="height: 2.176ex; vertical-align: -0.338ex; width: 1.636ex;" /></span></span> is the <a href="https://en.wikipedia.org/wiki/Kelvin" title="Kelvin">absolute temperature</a>. Thus, for <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Exothermic" title="Exothermic">exothermic</a> reactions, the standard <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Enthalpy_change" title="Enthalpy change">enthalpy change</a>, <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>H</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta H^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e7ca2ac7d655e35bf2076604abc115a3fe696542" style="height: 2.509ex; vertical-align: -0.338ex; width: 5.55ex;" /></span></span>, is negative and <i>K</i> decreases with temperature. For <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Endothermic" title="Endothermic">endothermic</a> reactions, <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>H</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta H^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e7ca2ac7d655e35bf2076604abc115a3fe696542" style="height: 2.509ex; vertical-align: -0.338ex; width: 5.55ex;" /></span></span> is positive and <i>K</i> increases with temperature.
</p><p>The standard enthalpy change for a reaction is itself a function of temperature, according to <a href="https://en.wikipedia.org/wiki/Gustav_Kirchhoff#Kirchhoff's_law_of_thermochemistry" title="Gustav Kirchhoff">Kirchhoff's law of thermochemistry</a>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mo>(</mo>
<mrow>
<mfrac>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi mathvariant="normal">Δ</mi>
<mi>H</mi>
</mrow>
<mrow>
<mi mathvariant="normal">∂</mi>
<mi>T</mi>
</mrow>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<mo>=</mo>
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>C</mi>
<mrow>
<mi>p</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \left({\frac {\partial \Delta H}{\partial T}}\right)_{p}=\Delta C_{p}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d06ed13b448cfda5772760db7d3868f4678ab082" style="height: 6.509ex; vertical-align: -2.838ex; width: 18.389ex;" /></span></dd></dl>
<p>where <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msub>
<mi>C</mi>
<mrow>
<mi>p</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta C_{p}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1f6a236977c534e28e77d59220129c54e9da4690" style="height: 2.843ex; vertical-align: -1.005ex; width: 4.657ex;" /></span></span> is the <a href="https://en.wikipedia.org/wiki/Specific_heat_capacity" title="Specific heat capacity">heat capacity</a> change at constant pressure. In practice <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>H</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta H^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e7ca2ac7d655e35bf2076604abc115a3fe696542" style="height: 2.509ex; vertical-align: -0.338ex; width: 5.55ex;" /></span></span> may be taken to be constant over a small temperature range.
</p>
<h3><span class="mw-headline" id="Dimensionality">Dimensionality</span></h3><p>In the equation
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">A</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">H</mi>
<mi mathvariant="normal">A</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\mathrm {a} }=\mathrm {\frac {[A^{-}][H^{+}]}{[HA]}} ,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/441ece0dee32e0a14fe14d4b1678785804486a92" style="height: 6.509ex; vertical-align: -2.671ex; width: 16.704ex;" /></span></dd></dl>
<p><i>K</i><sub>a</sub> appears to have <a href="https://en.wikipedia.org/wiki/Dimensional_analysis" title="Dimensional analysis">dimensions</a> of concentration. However, since <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<mi>G</mi>
<mo>=</mo>
<mo>−</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<mi>K</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G=-RT\ln K}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7b9e5ff562d6c5f44406b558c9cc8186884866ee" style="height: 2.343ex; vertical-align: -0.505ex; width: 16.849ex;" /></span>, the equilibrium constant, <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>K</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2b76fce82a62ed5461908f0dc8f037de4e3686b0" style="height: 2.176ex; vertical-align: -0.338ex; width: 2.066ex;" /></span></span>, <i>cannot</i> have a physical dimension. This apparent paradox can be resolved in various ways.
</p>
<ol><li>Assume that the quotient of activity coefficients has a numerical value of 1, so that <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>K</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2b76fce82a62ed5461908f0dc8f037de4e3686b0" style="height: 2.176ex; vertical-align: -0.338ex; width: 2.066ex;" /></span></span> has the same numerical value as the thermodynamic equilibrium constant <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msup>
<mi>K</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1f45734886910651b2143da8310f2b6a094327a4" style="height: 2.509ex; vertical-align: -0.338ex; width: 3.605ex;" /></span>.</li><li>Express each concentration value as the ratio c/c<sup>0</sup>, where c<sup>0</sup> is the concentration in a [hypothetical] standard state, with a numerical value of 1, by definition.</li><li>Express the concentrations on the <a href="https://en.wikipedia.org/wiki/Mole_fraction" title="Mole fraction">mole fraction</a> scale. Since mole fraction has no dimension, the quotient of concentrations will, by definition, be a pure number.</li></ol>
<p>The procedures, (1) and (2), give identical numerical values for an equilibrium constant. Furthermore, since a concentration <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>c</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle c_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/01acb7953ba52c2aa44264b5d0f8fd223aa178a2" style="height: 2.009ex; vertical-align: -0.671ex; width: 1.807ex;" /></span></span> is simply proportional to mole fraction <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle x_{i}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e87000dd6142b81d041896a30fe58f0c3acb2158" style="height: 2.009ex; vertical-align: -0.671ex; width: 2.129ex;" /></span></span> and density <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>ρ</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \rho }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1f7d439671d1289b6a816e6af7a304be40608d64" style="height: 2.176ex; vertical-align: -0.838ex; width: 1.202ex;" /></span></span>:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>c</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<msub>
<mi>x</mi>
<mrow>
<mi>i</mi>
</mrow>
</msub>
<mi>ρ</mi>
</mrow>
<mi>M</mi>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle c_{i}={\frac {x_{i}\rho }{M}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/bae7c8cd99d0ec4bc524b1badfb6c4d05aa63cc7" style="height: 4.843ex; vertical-align: -1.838ex; width: 9.072ex;" /></span></dd></dl>
<p>and since the molar mass <span class="nowrap"><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>M</mi>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle M}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f82cade9898ced02fdd08712e5f0c0151758a0dd" style="height: 2.176ex; vertical-align: -0.338ex; width: 2.442ex;" /></span></span>
is a constant in dilute solutions, an equilibrium constant value
determined using (3) will be simply proportional to the values obtained
with (1) and (2).
</p><p>It is common practice in <a href="https://en.wikipedia.org/wiki/Biochemistry" title="Biochemistry">biochemistry</a> to quote a value with a dimension as, for example, "<i>K</i><sub>a</sub> = 30 mM" in order to indicate the scale, millimolar (mM) or micromolar (μM) of the <a href="https://en.wikipedia.org/wiki/Concentration" title="Concentration">concentration</a> values used for its calculation.
</p>
<h2><span class="mw-headline" id="Strong_acids_and_bases">Strong acids and bases</span></h2><p>An acid is classified as "strong" when the concentration of its undissociated species is too low to be measured. Any aqueous acid with a p<i>K</i><sub>a</sub> value of less than 0 is almost completely deprotonated and is considered a <i>strong acid</i>. All such acids transfer their protons to water and form the solvent cation species (H<sub>3</sub>O<sup>+</sup> in aqueous solution) so that they all have essentially the same acidity, a phenomenon known as <a href="https://en.wikipedia.org/wiki/Leveling_effect" title="Leveling effect">solvent leveling</a>. They are said to be <i>fully dissociated</i> in aqueous solution because the amount of undissociated acid, in equilibrium with the dissociation products, is below the <a href="https://en.wikipedia.org/wiki/Detection_limit" title="Detection limit">detection limit</a>. Likewise, any aqueous base with an <a class="mw-selflink-fragment" href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#Bases_and_basicity">association constant</a> p<i>K</i><sub>b</sub> less than about 0, corresponding to p<i>K</i><sub>a</sub> greater than about 14, is leveled to OH<sup>−</sup> and is considered a <i>strong base</i>.
</p><p><a href="https://en.wikipedia.org/wiki/Nitric_acid" title="Nitric acid">Nitric acid</a>, with a p<i>K</i> value of around −1.7, behaves as a strong acid in aqueous solutions with a pH greater than 1. At lower pH values it behaves as a weak acid.
</p><p>p<i>K</i><sub>a</sub> values for strong acids have been estimated by theoretical means. For example, the p<i>K</i><sub>a</sub> value of aqueous <a href="https://en.wikipedia.org/wiki/Hydrochloric_acid" title="Hydrochloric acid">HCl</a> has been estimated as −9.3.
</p>
<h2><span class="mw-headline" id="Monoprotic_acids">Monoprotic acids</span></h2><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Acid#Monoprotic_acids" title="Acid">Acid § Monoprotic acids</a></div>
<figure class="mw-halign-right"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Weak_acid_speciation.svg"><img alt="This figure plots the relative fractions of the protonated form A H of an acid to its deprotonated form, A minus, as the solution p H is varied about the value of the acid's p K A. When the p H equals the p K a, the amounts of the protonated and deprotonated forms are equal. When the p H is one unit higher than the p K A, the ratio of concentrations of protonated to deprotonated forms is 10 to 1. When the p H is two units higher that ratio is 100 to 1. Conversely, when the p H is one or two unit lower than the p K A, the ratio is 1 to ten or 1 to 100. The exact percentage of each form may be determined from the Henderson–Hasselbalch equation." class="mw-file-element" data-file-height="400" data-file-width="400" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Weak_acid_speciation.svg/200px-Weak_acid_speciation.svg.png" width="400" /></a><figcaption>Variation of the % formation of a monoprotic acid, AH, and its conjugate base, A<sup>−</sup>, with the difference between the pH and the p<i>K</i><sub>a</sub> of the acid.</figcaption></figure>
<p>After rearranging the expression defining <i>K</i><sub>a</sub>, and putting <span class="nowrap">pH = −log<sub>10</sub>[H<sup>+</sup>]</span>, one obtains
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
<mi mathvariant="normal">H</mi>
</mrow>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>+</mo>
<mi>log</mi>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">A</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">H</mi>
<mi mathvariant="normal">A</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {pH} =\mathrm {p} K_{\text{a}}+\log \mathrm {\frac {[A^{-}]}{[HA]}} }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/25e874f2b8ea8e4127605788c356393cfd7fff37" style="height: 6.509ex; vertical-align: -2.671ex; width: 22.269ex;" /></span></dd></dl>
<p>This is the <a href="https://en.wikipedia.org/wiki/Henderson%E2%80%93Hasselbalch_equation" title="Henderson–Hasselbalch equation">Henderson–Hasselbalch equation</a>, from which the following conclusions can be drawn.
</p>
<ul><li>At half-neutralization the ratio <span class="nowrap"><span class="sfrac"><span class="tion"><span class="num">[A<sup>−</sup>]</span><span class="sr-only">/</span><span class="den">[HA]</span></span></span> = 1</span>; since <span class="nowrap">log(1) = 0</span>, the pH at half-neutralization is numerically equal to p<i>K</i><sub>a</sub>. Conversely, when <span class="nowrap">pH = p<i>K</i><sub>a</sub></span>, the concentration of HA is equal to the concentration of A<sup>−</sup>.</li><li>The <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">buffer region</a> extends over the approximate range p<i>K</i><sub>a</sub> ± 2. Buffering is weak outside the range p<i>K</i><sub>a</sub> ± 1. At pH ≤ p<i>K</i><sub>a</sub> − 2 the substance is said to be fully protonated and at pH ≥ p<i>K</i><sub>a</sub> + 2 it is fully dissociated (deprotonated).</li><li>If the pH is known, the ratio may be calculated. This ratio is independent of the analytical concentration of the acid.</li></ul>
<p>In water, measurable p<i>K</i><sub>a</sub> values range from about −2 for a strong acid to about 12 for a very weak acid (or strong base).
</p><p>A <a href="https://en.wikipedia.org/wiki/Buffer_solution" title="Buffer solution">buffer solution</a>
of a desired pH can be prepared as a mixture of a weak acid and its
conjugate base. In practice, the mixture can be created by dissolving
the acid in water, and adding the requisite amount of strong acid or
base. When the p<i>K</i><sub>a</sub> and analytical concentration of the
acid are known, the extent of dissociation and pH of a solution of a
monoprotic acid can be easily calculated using an <a class="mw-redirect" href="https://en.wikipedia.org/wiki/ICE_table" title="ICE table">ICE table</a>.
</p>
<h2><span class="mw-headline" id="Polyprotic_acids">Polyprotic acids</span></h2><figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:H3PO4_speciation.png"><img alt="Acids with more than one ionizable hydrogen atoms are called polyprotic acids, and have multiple deprotonation states, also called species. This image plots the relative percentages of the different protonation species of phosphoric acid H 3 P O 4 as a function of solution p H. Phosphoric acid has three ionizable hydrogen atoms whose p K A's are roughly 2, 7 and 12. Below p H 2, the triply protonated species H 3 P O 4 predominates; the double protonated species H 2 P O 4 minus predominates near p H 5; the singly protonated species H P O 4 2 minus predominates near p H 9 and the unprotonated species P O 4 3 minus predominates above p H 12" class="mw-file-element" data-file-height="349" data-file-width="350" height="199" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/16/H3PO4_speciation.png/200px-H3PO4_speciation.png" width="200" /></a><figcaption>Phosphoric acid speciation</figcaption></figure>
<p>A polyprotic acid is a compound which may lose more than 1 proton.
Stepwise dissociation constants are each defined for the loss of a
single proton. The constant for dissociation of the first proton may be
denoted as <i>K</i><sub>a1</sub> and the constants for dissociation of successive protons as <i>K</i><sub>a2</sub>, etc. <a href="https://en.wikipedia.org/wiki/Phosphoric_acid" title="Phosphoric acid">Phosphoric acid</a>, <span class="chemf nowrap">H<sub class="template-chem2-sub">3</sub>PO<sub class="template-chem2-sub">4</sub></span>, is an example of a polyprotic acid as it can lose three protons.
</p>
<dl><dd><table class="wikitable">
<tbody><tr>
<th>Equilibrium
</th>
<th>p<i>K</i> definition and value
</th></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H3PO4 <=> H2PO4- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0bad230e36d044bc40cd6e601449ac3f51492584" style="height: 3.343ex; vertical-align: -1.005ex; width: 25.684ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>1</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mn>2.14</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{{\ce {a1}}}=\log _{10}{\frac {[{\ce {H_3PO_4}}]}{[{\ce {H_2PO_4^{-}}}][{\ce {H^+}}]}}=2.14}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/dff6e67381cb8a691b8873fbf884dad30b001352" style="height: 7.009ex; vertical-align: -3.005ex; width: 35.094ex;" /></span>
</td></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>HPO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2PO4- <=> HPO4^2- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/89871c24183c4690cfb8474b6c32f74ac1a9e05f" style="height: 3.343ex; vertical-align: -1.005ex; width: 25.908ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>HPO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mspace width="thinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mn>7.2</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{{\ce {a2}}}=\log _{10}{\frac {[{\ce {H_2PO_4^{-}}}]}{[{\ce {HPO_4^{2-}}}][{\ce {H^+}}]}}=7.2}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/efe9f5a620a62c8de4a6567f58faf01e66829903" style="height: 7.176ex; vertical-align: -3.005ex; width: 34.086ex;" /></span>
</td></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>HPO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>3</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HPO4^2- <=> PO4^3- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2cd229dc9b810e10d869d9955b0661aec845dfc4" style="height: 3.176ex; vertical-align: -0.838ex; width: 23.933ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<msubsup>
<mtext>a</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>HPO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msubsup>
<mtext>PO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>3</mn>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mn>12.37</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{{\ce {a3}}}=\log _{10}{\frac {[{\ce {HPO4^2-}}]}{[{\ce {PO4^3-}}][{\ce {H+}}]}}=12.37}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/dfac57be595c190a1dc60479c2538e575488de02" style="height: 7.176ex; vertical-align: -3.005ex; width: 34.281ex;" /></span>
</td></tr></tbody></table></dd></dl>
<p>When the difference between successive p<i>K</i> values is about four or more, as in this example, each species may be considered as an acid in its own right; In fact salts of <span class="chemf nowrap">H<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span>PO<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">−</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">4</sub></span></span> may be crystallised from solution by adjustment of pH to about 5.5 and salts of <span class="chemf nowrap">HPO<span class="template-chem2-su"><span>2−</span><span>4</span></span></span>
may be crystallised from solution by adjustment of pH to about 10. The
species distribution diagram shows that the concentrations of the two
ions are maximum at pH 5.5 and 10.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Citric_acid_speciation.png"><img alt="This image plots the relative percentages of the protonation species of citric acid as a function of p H. Citric acid has three ionizable hydrogen atoms and thus three p K A values. Below the lowest p K A, the triply protonated species prevails; between the lowest and middle p K A, the doubly protonated form prevails; between the middle and highest p K A, the singly protonated form prevails; and above the highest p K A, the unprotonated form of citric acid is predominant." class="mw-file-element" data-file-height="248" data-file-width="242" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Citric_acid_speciation.png/200px-Citric_acid_speciation.png" width="390" /></a><figcaption>% species formation calculated with the program HySS for a 10 millimolar solution of citric acid. p<i>K</i><sub>a1</sub> = 3.13, p<i>K</i><sub>a2</sub> = 4.76, p<i>K</i><sub>a3</sub> = 6.40.</figcaption></figure>
<p>When the difference between successive p<i>K</i> values is less than
about four there is overlap between the pH range of existence of the
species in equilibrium. The smaller the difference, the more the
overlap. The case of citric acid is shown at the right; solutions of
citric acid are buffered over the whole range of pH 2.5 to 7.5.
</p><p>According to Pauling's first rule, successive p<i>K</i> values of a given acid increase <span class="nowrap">(p<i>K</i><sub>a2</sub> > p<i>K</i><sub>a1</sub>)</span>. For oxyacids with more than one ionizable hydrogen on the same atom, the p<i>K</i><sub>a</sub> values often increase by about 5 units for each proton removed as in the example of phosphoric acid above.
</p><p>It can be seen in the table above that the second proton is
removed from a negatively charged species. Since the proton carries a
positive charge extra work is needed to remove it, which is why p<i>K</i><sub>a2</sub> is greater than p<i>K</i><sub>a1</sub>. p<i>K</i><sub>a3</sub> is greater than p<i>K</i><sub>a2</sub>
because there is further charge separation. When an exception to
Pauling's rule is found, it indicates that a major change in structure
is also occurring. In the case of <span class="chemf nowrap">VO<span class="template-chem2-su"><span>+</span><span>2</span></span></span>(aq), the vanadium is <a href="https://en.wikipedia.org/wiki/Octahedral_molecular_geometry" title="Octahedral molecular geometry">octahedral</a>, 6-coordinate, whereas vanadic acid is <a href="https://en.wikipedia.org/wiki/Tetrahedral_molecular_geometry" title="Tetrahedral molecular geometry">tetrahedral</a>,
4-coordinate. This means that four "particles" are released with the
first dissociation, but only two "particles" are released with the other
dissociations, resulting in a much greater entropy contribution to the
standard <a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy">Gibbs free energy</a> change for the first reaction than for the others.
</p>
<dl><dd><table class="wikitable">
<tbody><tr>
<th>Equilibrium
</th>
<th>p<i>K</i><sub>a</sub>
</th></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msup>
<mrow>
<mo stretchy="false">[</mo>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<mn>2</mn>
<mspace width="thinmathspace"></mspace>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {[VO2(H2O)4]+ <=> H3VO4 + H+ + 2H2O}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0b5fcdc28e4fbd98292ebd608643c231844a334f" style="height: 3.343ex; vertical-align: -1.005ex; width: 42.02ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<msub>
<mi>a</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
</mrow>
</msub>
<mo>=</mo>
<mn>4.2</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{a_{1}}=4.2}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/28b393fc50b631df90fcfacfa693c90a025e6aa7" style="height: 2.843ex; vertical-align: -1.005ex; width: 11.269ex;" /></span>
</td></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H3VO4 <=> H2VO4- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/82e204dede10cc8bbe3c5c9f9ec19aad64e86744" style="height: 3.343ex; vertical-align: -1.005ex; width: 26.005ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<msub>
<mi>a</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mrow>
</msub>
<mo>=</mo>
<mn>2.60</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{a_{2}}=2.60}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af1888cdc26d9e44faa685dc70d5d80912fefab1" style="height: 2.843ex; vertical-align: -1.005ex; width: 12.432ex;" /></span>
</td></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>HVO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2VO4- <=> HVO4^2- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/74f85df8ae3b991e20e4904d2557c71d49b180fa" style="height: 3.343ex; vertical-align: -1.005ex; width: 26.229ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<msub>
<mi>a</mi>
<mrow>
<mn>3</mn>
</mrow>
</msub>
</mrow>
</msub>
<mo>=</mo>
<mn>7.92</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{a_{3}}=7.92}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/34d0bc69b5eb7539adb49838a4343fb83bee0611" style="height: 2.843ex; vertical-align: -1.005ex; width: 12.432ex;" /></span>
</td></tr>
<tr>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>HVO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>VO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mn>3</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HVO4^2- <=> VO4^3- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/58d9b1ee5e0e1420119a8705d09be0bdabfaa667" style="height: 3.176ex; vertical-align: -0.838ex; width: 24.253ex;" /></span>
</td>
<td><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<msub>
<mi>a</mi>
<mrow>
<mn>4</mn>
</mrow>
</msub>
</mrow>
</msub>
<mo>=</mo>
<mn>13.27</mn>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{a_{4}}=13.27}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8dd1d0fec6059a861f48a57f6e4e02bea7680f9b" style="height: 2.843ex; vertical-align: -1.005ex; width: 13.594ex;" /></span>
</td></tr></tbody></table></dd></dl>
<h3><span class="mw-headline" id="Isoelectric_point">Isoelectric point</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Isoelectric_point" title="Isoelectric point">isoelectric point</a></div>
<p>For substances in solution, the isoelectric point (p<i>I</i>) is
defined as the pH at which the sum, weighted by charge value, of
concentrations of positively charged species is equal to the weighted
sum of concentrations of negatively charged species. In the case that
there is one species of each type, the isoelectric point can be obtained
directly from the p<i>K</i> values. Take the example of <a href="https://en.wikipedia.org/wiki/Glycine" title="Glycine">glycine</a>, defined as AH. There are two dissociation equilibria to consider.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>AH</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<mtext>AH</mtext>
<mtext> </mtext>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mspace width="2em"></mspace>
<mrow>
<mo stretchy="false">[</mo>
<mtext>AH</mtext>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo>=</mo>
</mrow>
<msubsup>
<mrow>
<mrow>
<mtext mathvariant="italic">K</mtext>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mo stretchy="false">[</mo>
<msubsup>
<mtext>AH</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {AH2+<=>AH~+H+\qquad [AH][H+]={\mathit {K}}_{1}[AH2+]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/359f1d34ddc5ac4b4cecf45e11539bc14462e98f" style="height: 3.343ex; vertical-align: -1.005ex; width: 44.719ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>AH</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mtext> </mtext>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mspace width="2em"></mspace>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo>=</mo>
</mrow>
<msubsup>
<mrow>
<mrow>
<mtext mathvariant="italic">K</mtext>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mo stretchy="false">[</mo>
<mtext>AH</mtext>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {AH<=>A^{-}~+H+\qquad [A^{-}][H+]={\mathit {K}}_{2}[AH]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/95c1af1bef047675675659473e3886aefff9fa79" style="height: 3.343ex; vertical-align: -1.005ex; width: 41.233ex;" /></span></dd></dl>
<p>Substitute the expression for [AH] from the second equation into the first equation
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>A</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<msup>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
</msup>
<mrow>
<mo>=</mo>
</mrow>
<msubsup>
<mrow>
<mrow>
<mtext mathvariant="italic">K</mtext>
</mrow>
</mrow>
<mrow>
<mn>1</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mrow>
<mrow>
<mtext mathvariant="italic">K</mtext>
</mrow>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mrow>
<mo stretchy="false">[</mo>
<msubsup>
<mtext>AH</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">]</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {[A^{-}][H+]^{2}={\mathit {K}}_{1}{\mathit {K}}_{2}[AH2+]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/473772e02e925c83975026ce31b43a0a2dc4b1cc" style="height: 3.676ex; vertical-align: -1.005ex; width: 23.931ex;" /></span></dd></dl>
<p>At the isoelectric point the concentration of the positively charged species, <span class="chemf nowrap">AH<span class="template-chem2-su"><span>+</span><span>2</span></span></span>, is equal to the concentration of the negatively charged species, <span class="chemf nowrap">A<sup class="template-chem2-sup">−</sup></span>, so
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mn>2</mn>
</mrow>
</msup>
<mo>=</mo>
<msub>
<mi>K</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<msub>
<mi>K</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {H+}}]^{2}=K_{1}K_{2}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3dfa9985f2d6769f35f98f98153ac6cabd9c011b" style="height: 3.176ex; vertical-align: -0.838ex; width: 14.755ex;" /></span></dd></dl>
<p>Therefore, taking <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cologarithm" title="Cologarithm">cologarithms</a>, the pH is given by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<mi>I</mi>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mn>1</mn>
</mrow>
</msub>
<mo>+</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} I={\frac {\mathrm {p} K_{1}+\mathrm {p} K_{2}}{2}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cc00e052fe0c877eb4bc071b443d0d26cb6e23fa" style="height: 5.343ex; vertical-align: -1.838ex; width: 17.879ex;" /></span></dd></dl>
<p>p<i>I</i> values for amino acids are listed at <a href="https://en.wikipedia.org/wiki/Proteinogenic_amino_acid#Chemical_properties" title="Proteinogenic amino acid">proteinogenic amino acid</a>. When more than two charged species are in equilibrium with each other a full speciation calculation may be needed.
</p>
<h2><span class="mw-headline" id="Bases_and_basicity">Bases and basicity</span></h2><p>The equilibrium constant <i>K</i><sub>b</sub> for a base is usually defined as the <i>association</i> constant for protonation of the base, B, to form the conjugate acid, <span class="chemf nowrap">HB<sup class="template-chem2-sup">+</sup></span>.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>B</mtext>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>HB</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {B + H2O <=> HB+ + OH-}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/909f5ab4aba71c3ae912189c432d4cbbc5f053f7" style="height: 3.343ex; vertical-align: -1.005ex; width: 26.541ex;" /></span></dd></dl>
<p>Using similar reasoning to that used before
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtable columnalign="right left right left right left right left right left right left" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true" rowspacing="3pt">
<mtr>
<mtd>
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">H</mi>
<msup>
<mi mathvariant="normal">B</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">O</mi>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">B</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mtd>
</mtr>
<mtr>
<mtd>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
</mtd>
<mtd>
<mi></mi>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mo>(</mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
<mo>)</mo>
</mrow>
</mtd>
</mtr>
</mtable>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\begin{aligned}K_{\text{b}}&=\mathrm {\frac {[HB^{+}][OH^{-}]}{[B]}} \\\mathrm {p} K_{\text{b}}&=-\log _{10}\left(K_{\text{b}}\right)\end{aligned}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5dea1aac629a595476e18c042a8f4365a50f0efc" style="height: 9.509ex; vertical-align: -4.171ex; width: 21.647ex;" /></span></dd></dl>
<p><i>K</i><sub>b</sub> is related to <i>K</i><sub>a</sub> for the conjugate acid. In water, the concentration of the <a href="https://en.wikipedia.org/wiki/Hydroxide" title="Hydroxide">hydroxide</a> ion, <span class="chemf nowrap">[OH<sup class="template-chem2-sup">−</sup>]</span>, is related to the concentration of the hydrogen ion by <span class="chemf nowrap"><i>K</i><sub class="template-chem2-sub">w</sub> = [H<sup class="template-chem2-sup">+</sup>][OH<sup class="template-chem2-sup">−</sup>]</span>, therefore
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">O</mi>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">w</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {[OH^{-}]} ={\frac {K_{\mathrm {w} }}{\mathrm {[H^{+}]} }}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ab7f583da9f8b50145990ffa4342919930edfa16" style="height: 6.009ex; vertical-align: -2.671ex; width: 14.838ex;" /></span></dd></dl>
<p>Substitution of the expression for <span class="chemf nowrap">[OH<sup class="template-chem2-sup">−</sup>]</span> into the expression for <i>K</i><sub>b</sub> gives
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<mi mathvariant="normal">H</mi>
<msup>
<mi mathvariant="normal">B</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>w</mtext>
</mrow>
</msub>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">B</mi>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mo>=</mo>
<mrow>
<mfrac>
<msub>
<mi>K</mi>
<mrow>
<mtext>w</mtext>
</mrow>
</msub>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{b}}={\frac {[\mathrm {HB^{+}} ]K_{\text{w}}}{\mathrm {[B][H^{+}]} }}={\frac {K_{\text{w}}}{K_{\text{a}}}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/921c3abd37a1c5c00c31831509d3b090394c0d47" style="height: 6.509ex; vertical-align: -2.671ex; width: 23.965ex;" /></span></dd></dl>
<p>When <i>K</i><sub>a</sub>, <i>K</i><sub>b</sub> and <i>K</i><sub>w</sub> are determined under the same conditions of temperature and ionic strength, it follows, taking <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cologarithm" title="Cologarithm">cologarithms</a>, that p<i>K</i><sub>b</sub> = p<i>K</i><sub>w</sub> − p<i>K</i><sub>a</sub>. In aqueous solutions at 25 °C, p<i>K</i><sub>w</sub> is 13.9965, so
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
<mo>≈</mo>
<mn>14</mn>
<mo>−</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{\text{b}}\approx 14-\mathrm {p} K_{\text{a}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/89c6f4054b89ffac08989faf2fb0fc6ed9429300" style="height: 2.509ex; vertical-align: -0.671ex; width: 16.995ex;" /></span></dd></dl>
<p>with sufficient <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Accuracy" title="Accuracy">accuracy</a> for most practical purposes. In effect there is no need to define p<i>K</i><sub>b</sub> separately from p<i>K</i><sub>a</sub>, but it is done here as often only p<i>K</i><sub>b</sub> values can be found in the older literature.
</p><p>For an hydrolyzed metal ion, <i>K</i><sub>b</sub> can also be defined as a stepwise <i>dissociation</i> constant
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow>
<mi mathvariant="normal">M</mi>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<mtext>OH</mtext>
</mrow>
<msub>
<mo stretchy="false">)</mo>
<mrow>
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">⇋</mo>
<msub>
<mrow>
<mi mathvariant="normal">M</mi>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<mtext>OH</mtext>
</mrow>
<msubsup>
<mo stretchy="false">)</mo>
<mrow>
<mi>q</mi>
<mo>−</mo>
<mn>1</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo>+</mo>
<mrow>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {M} _{p}({\ce {OH}})_{q}\leftrightharpoons \mathrm {M} _{p}({\ce {OH}})_{q-1}^{+}+{\ce {OH-}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cc046f39d1702f6efb4a190f22413ff10a392843" style="height: 3.509ex; vertical-align: -1.338ex; width: 32.695ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">b</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msub>
<mrow>
<mi mathvariant="normal">M</mi>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<mtext>OH</mtext>
</mrow>
<msubsup>
<mo stretchy="false">)</mo>
<mrow>
<mi>q</mi>
<mo>−</mo>
<mn>1</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msub>
<mrow>
<mi mathvariant="normal">M</mi>
</mrow>
<mrow>
<mi>p</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<mtext>OH</mtext>
</mrow>
<msub>
<mo stretchy="false">)</mo>
<mrow>
<mi>q</mi>
</mrow>
</msub>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\mathrm {b} }={\frac {[\mathrm {M} _{p}({\ce {OH}})_{q-1}^{+}][{\ce {OH-}}]}{[\mathrm {M} _{p}({\ce {OH}})_{q}]}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8391968e700e57f56f6041dd839f0fdb5e93780e" style="height: 7.176ex; vertical-align: -2.671ex; width: 26.343ex;" /></span></dd></dl>
<p>This is the reciprocal of an <a href="https://en.wikipedia.org/wiki/Stability_constants_of_complexes" title="Stability constants of complexes">association constant</a> for formation of the complex.
</p>
<h3><span class="mw-headline" id="Basicity_expressed_as_dissociation_constant_of_conjugate_acid">Basicity expressed as dissociation constant of conjugate acid</span></h3><p>Because the relationship p<i>K</i><sub>b</sub> = p<i>K</i><sub>w</sub> − p<i>K</i><sub>a</sub>
holds only in aqueous solutions (though analogous relationships apply
for other amphoteric solvents), subdisciplines of chemistry like <a href="https://en.wikipedia.org/wiki/Organic_chemistry" title="Organic chemistry">organic chemistry</a> that usually deal with nonaqueous solutions generally do not use p<i>K</i><sub>b</sub> as a measure of basicity. Instead, the p<i>K</i><sub>a</sub> of the conjugate acid, denoted by p<i>K</i><sub>aH</sub>, is quoted when basicity needs to be quantified. For base B and its conjugate acid BH<sup>+</sup> in equilibrium, this is defined as
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
<mi mathvariant="normal">H</mi>
</mrow>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<mi mathvariant="normal">B</mi>
</mrow>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mrow>
<msup>
<mtext>BH</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">(</mo>
</mrow>
</mrow>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<mtext>B</mtext>
</mrow>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<mrow>
<msup>
<mtext>BH</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
<mrow>
<mrow>
<mo maxsize="1.623em" minsize="1.623em">)</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{\mathrm {aH} }(\mathrm {B} )=\mathrm {p} K_{\mathrm {a} }({\ce {BH+}})=-\log _{10}{\Big (}{\frac {[{\ce {B}}][{\ce {H+}}]}{[{\ce {BH+}}]}}{\Big )}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b76149bc3dbc3d0375d6355bdf2342394a568776" style="height: 6.843ex; vertical-align: -2.838ex; width: 44.761ex;" /></span></dd></dl>
<p>A higher value for p<i>K</i><sub>aH</sub> corresponds to a stronger base. For example, the values <span class="chemf nowrap">p<i>K</i><sub class="template-chem2-sub">aH</sub> (C<sub class="template-chem2-sub">5</sub>H<sub class="template-chem2-sub">5</sub>N) = 5.25</span> and <span class="chemf nowrap">p<i>K</i><sub class="template-chem2-sub">aH</sub> ((CH<sub class="template-chem2-sub">3</sub>CH<sub class="template-chem2-sub">2</sub>)<sub class="template-chem2-sub">3</sub>N) = 10.75</span> indicate that <span class="chemf nowrap">(CH<sub class="template-chem2-sub">3</sub>CH<sub class="template-chem2-sub">2</sub>)<sub class="template-chem2-sub">3</sub>N</span> (triethylamine) is a stronger base than <span class="chemf nowrap">C<sub class="template-chem2-sub">5</sub>H<sub class="template-chem2-sub">5</sub>N</span> (pyridine).
</p>
<h2><span class="mw-headline" id="Amphoteric_substances">Amphoteric substances</span></h2><p>An <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Amphoteric" title="Amphoteric">amphoteric</a>
substance is one that can act as an acid or as a base, depending on pH.
Water (below) is amphoteric. Another example of an amphoteric molecule
is the <a href="https://en.wikipedia.org/wiki/Bicarbonate" title="Bicarbonate">bicarbonate</a> ion <span class="chemf nowrap">HCO<span class="template-chem2-su"><span>−</span><span>3</span></span></span> that is the conjugate base of the <a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">carbonic acid</a> molecule H2CO3 in the equilibrium
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>CO</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>HCO</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msup>
<mtext>O</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2CO3 + H2O <=> HCO3- + H3O+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/057b8f579fd09792e0d83547ee505be9c67961fa" style="height: 3.343ex; vertical-align: -1.005ex; width: 35.128ex;" /></span></dd></dl>
<p>but also the conjugate acid of the <a href="https://en.wikipedia.org/wiki/Carbonate" title="Carbonate">carbonate</a> ion <span class="chemf nowrap">CO<span class="template-chem2-su"><span>2−</span><span>3</span></span></span> in (the reverse of) the equilibrium
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>HCO</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>CO</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mn>2</mn>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HCO3- + OH- <=> CO3^2- + H2O}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7a0bedf8d26dbac0831641468cf29d710bee152d" style="height: 3.343ex; vertical-align: -1.005ex; width: 32.555ex;" /></span></dd></dl>
<p><a href="https://en.wikipedia.org/wiki/Carbonic_acid" title="Carbonic acid">Carbonic acid</a> equilibria are important for <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis" title="Acid–base homeostasis">acid–base homeostasis</a> in the human body.
</p><p>An <a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acid</a>
is also amphoteric with the added complication that the neutral
molecule is subject to an internal acid–base equilibrium in which the
basic amino group attracts and binds the proton from the acidic carboxyl
group, forming a <a href="https://en.wikipedia.org/wiki/Zwitterion" title="Zwitterion">zwitterion</a>.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>H</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {NH2CHRCO2H <=> NH3+CHRCO2-}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/90fcae69e091ad28ca99b4d7db1e70fbc1260543" style="height: 3.343ex; vertical-align: -1.005ex; width: 35.73ex;" /></span></dd></dl>
<p>At pH less than about 5 both the carboxylate group and the amino
group are protonated. As pH increases the acid dissociates according to
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>H</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {NH3+CHRCO2H <=> NH3+CHRCO2- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c57b18b588663ab6f1663f7d0bfdea438f7563a7" style="height: 3.343ex; vertical-align: -1.005ex; width: 42.28ex;" /></span></dd></dl>
<p>At high pH a second dissociation may take place.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>CHRCO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {NH3+CHRCO2- <=> NH2CHRCO2- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9a35edad84394fb2ee02b77a37b459630b77c990" style="height: 3.343ex; vertical-align: -1.005ex; width: 40.537ex;" /></span></dd></dl>
<p>Thus the amino acid molecule is amphoteric because it may either be protonated or deprotonated.
</p>
<h3><span class="mw-headline" id="Water_self-ionization">Water self-ionization</span></h3><div class="hatnote navigation-not-searchable" role="note">Main article: <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">Self-ionization of water</a></div>
<p>The water molecule may either gain or lose a proton. It is said to be <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Amphiprotic" title="Amphiprotic">amphiprotic</a>. The ionization equilibrium can be written
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>OH</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msup>
<mtext>H</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2O <=> OH- + H+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/108572cba335be22ebb605fb7a239fc81b08f8af" style="height: 3.343ex; vertical-align: -1.005ex; width: 20.41ex;" /></span></dd></dl>
<p>where in aqueous solution <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup></span> denotes a <a href="https://en.wikipedia.org/wiki/Solvation" title="Solvation">solvated</a> proton. Often this is written as the <a href="https://en.wikipedia.org/wiki/Hydronium" title="Hydronium">hydronium</a> ion <span class="chemf nowrap">H<sub class="template-chem2-sub">3</sub>O<sup class="template-chem2-sup">+</sup></span>, but this formula is not exact because in fact there is solvation by more than one water molecule and species such as <span class="chemf nowrap">H<sub class="template-chem2-sub">5</sub>O<span class="template-chem2-su"><span>+</span><span>2</span></span></span>, <span class="chemf nowrap">H<sub class="template-chem2-sub">7</sub>O<span class="template-chem2-su"><span>+</span><span>3</span></span></span>, and <span class="chemf nowrap">H<sub class="template-chem2-sub">9</sub>O<span class="template-chem2-su"><span>+</span><span>4</span></span></span> are also present.
</p><p>The equilibrium constant is given by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<mrow>
<mfrac>
<mrow>
<mo stretchy="false">[</mo>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<mi mathvariant="normal">O</mi>
<msup>
<mi mathvariant="normal">H</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
</mrow>
<mrow>
<mo stretchy="false">[</mo>
<msub>
<mi mathvariant="normal">H</mi>
<mrow>
<mn>2</mn>
</mrow>
</msub>
<mi mathvariant="normal">O</mi>
<mo stretchy="false">]</mo>
</mrow>
</mfrac>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{a}}=\mathrm {\frac {[H^{+}][OH^{-}]}{[H_{2}O]}} }" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cdc540ad193c8f1661c1897698be93153fc5fb84" style="height: 6.509ex; vertical-align: -2.671ex; width: 17.865ex;" /></span></dd></dl>
<p>With solutions in which the solute concentrations are not very high, the concentration <span class="chemf nowrap">[H<sub class="template-chem2-sub">2</sub>O]</span> can be assumed to be constant, regardless of solute(s); this expression may then be replaced by
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>w</mtext>
</mrow>
</msub>
<mo>=</mo>
<mo stretchy="false">[</mo>
<msup>
<mrow>
<mi mathvariant="normal">H</mi>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mo stretchy="false">[</mo>
<msup>
<mrow>
<mi mathvariant="normal">O</mi>
<mi mathvariant="normal">H</mi>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo stretchy="false">]</mo>
<mspace width="thinmathspace"></mspace>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{w}}=[\mathrm {H} ^{+}][\mathrm {OH} ^{-}]\,}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c0039f77db244ea2f6d03d3475dc7a232a8ccb16" style="height: 3.009ex; vertical-align: -0.838ex; width: 17.781ex;" /></span></dd></dl>
<p>The <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">self-ionization</a> constant of water, <i>K</i><sub>w</sub>, is thus just a special case of an acid dissociation constant. A logarithmic form analogous to p<i>K</i><sub>a</sub> may also be defined
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>w</mtext>
</mrow>
</msub>
<mo>=</mo>
<mo>−</mo>
<msub>
<mi>log</mi>
<mrow>
<mn>10</mn>
</mrow>
</msub>
<mo></mo>
<mrow>
<mo>(</mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>w</mtext>
</mrow>
</msub>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{\text{w}}=-\log _{10}\left(K_{\text{w}}\right)}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3326030fb01e3d9d08d2fd448abdffc14cb0d7fb" style="height: 2.843ex; vertical-align: -0.838ex; width: 20.027ex;" /></span></dd></dl>
<table border="1" style="text-align: center;">
<caption>p<i>K</i><sub>w</sub> values for pure water at various temperatures
</caption>
<tbody><tr>
<th scope="row"><i>T</i> (°C)
</th>
<td>0</td>
<td>5</td>
<td>10</td>
<td>15</td>
<td>20</td>
<td>25</td>
<td>30</td>
<td>35</td>
<td>40</td>
<td>45</td>
<td>50
</td></tr>
<tr>
<th scope="row">p<i>K</i><sub>w</sub>
</th>
<td>14.943</td>
<td>14.734</td>
<td>14.535</td>
<td>14.346</td>
<td>14.167</td>
<td>13.997</td>
<td>13.830</td>
<td>13.680</td>
<td>13.535</td>
<td>13.396</td>
<td>13.262
</td></tr></tbody></table>
<p>These data can be modelled by a <a href="https://en.wikipedia.org/wiki/Parabola" title="Parabola">parabola</a> with
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">w</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<mn>14.94</mn>
<mo>−</mo>
<mn>0.04209</mn>
<mtext> </mtext>
<mi>T</mi>
<mo>+</mo>
<mn>0.0001718</mn>
<mtext> </mtext>
<msup>
<mi>T</mi>
<mrow>
<mn>2</mn>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K_{\mathrm {w} }=14.94-0.04209\ T+0.0001718\ T^{2}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/af1d458dfa79379abc5541331924dd44a4968fd2" style="height: 3.009ex; vertical-align: -0.671ex; width: 41.9ex;" /></span></dd></dl>
<p>From this equation, p<i>K</i><sub>w</sub> = 14 at 24.87 °C. At that temperature both hydrogen and hydroxide ions have a concentration of 10<sup>−7</sup> M.
</p>
<h2><span class="mw-headline" id="Acidity_in_nonaqueous_solutions">Acidity in nonaqueous solutions</span></h2><p>A solvent will be more likely to promote ionization of a dissolved acidic molecule in the following circumstances:
</p>
<ol><li>It is a <a href="https://en.wikipedia.org/wiki/Protic_solvent" title="Protic solvent">protic solvent</a>, capable of forming hydrogen bonds.</li><li>It has a high <a href="https://en.wikipedia.org/wiki/Donor_number" title="Donor number">donor number</a>, making it a strong <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lewis_base" title="Lewis base">Lewis base</a>.</li><li>It has a high <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dielectric_constant" title="Dielectric constant">dielectric constant</a> (relative permittivity), making it a good solvent for ionic species.</li></ol>
<p>p<i>K</i><sub>a</sub> values of organic compounds are often obtained using the aprotic solvents <a href="https://en.wikipedia.org/wiki/Dimethyl_sulfoxide" title="Dimethyl sulfoxide">dimethyl sulfoxide</a> (DMSO) and <a href="https://en.wikipedia.org/wiki/Acetonitrile" title="Acetonitrile">acetonitrile</a> (ACN).
</p>
<table border="1">
<caption>Solvent properties at 25 °C
</caption>
<tbody><tr>
<th>Solvent</th>
<th>Donor number</th>
<th>Dielectric constant
</th></tr>
<tr>
<td>Acetonitrile</td>
<td>14</td>
<td>37
</td></tr>
<tr>
<td>Dimethylsulfoxide</td>
<td>30</td>
<td>47
</td></tr>
<tr>
<td>Water</td>
<td>18</td>
<td>78
</td></tr></tbody></table>
<p>DMSO is widely used as an alternative to water because it has a lower
dielectric constant than water, and is less polar and so dissolves
non-polar, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydrophobic" title="Hydrophobic">hydrophobic</a> substances more easily. It has a measurable p<i>K</i><sub>a</sub>
range of about 1 to 30. Acetonitrile is less basic than DMSO, and, so,
in general, acids are weaker and bases are stronger in this solvent.
Some p<i>K</i><sub>a</sub> values at 25 °C for acetonitrile (ACN and dimethyl sulfoxide (DMSO). are shown in the following tables. Values for water are included for comparison.
</p>
<table border="1">
<caption>p<i>K</i><sub>a</sub> values of acids
</caption>
<tbody><tr>
<th>HA ⇌ A<sup>−</sup> + H<sup>+</sup></th>
<th>ACN</th>
<th>DMSO</th>
<th>Water
</th></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/P-Toluenesulfonic_acid" title="P-Toluenesulfonic acid"><i>p</i>-Toluenesulfonic acid</a></td>
<td>8.5</td>
<td>0.9</td>
<td><i>Strong</i>
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/2,4-Dinitrophenol" title="2,4-Dinitrophenol">2,4-Dinitrophenol</a></td>
<td>16.66</td>
<td>5.1</td>
<td>3.9
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Benzoic_acid" title="Benzoic acid">Benzoic acid</a></td>
<td>21.51</td>
<td>11.1</td>
<td>4.2
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">Acetic acid</a></td>
<td>23.51</td>
<td>12.6</td>
<td>4.756
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Phenol" title="Phenol">Phenol</a></td>
<td>29.14</td>
<td>18.0</td>
<td>9.99
</td></tr>
<tr>
<th>BH<sup>+</sup> ⇌ B + H<sup>+</sup></th>
<th>ACN</th>
<th>DMSO</th>
<th>Water
</th></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Pyrrolidine" title="Pyrrolidine">Pyrrolidine</a></td>
<td>19.56</td>
<td>10.8</td>
<td>11.4
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Triethylamine" title="Triethylamine">Triethylamine</a></td>
<td>18.82</td>
<td>9.0</td>
<td>10.72
</td></tr>
<tr>
<td><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Proton_sponge" title="Proton sponge">Proton sponge</a><span class="nowrap"> </span></td>
<td>18.62</td>
<td>7.5</td>
<td>12.1
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Pyridine" title="Pyridine">Pyridine</a></td>
<td>12.53</td>
<td>3.4</td>
<td>5.2
</td></tr>
<tr>
<td><a href="https://en.wikipedia.org/wiki/Aniline" title="Aniline">Aniline</a></td>
<td>10.62</td>
<td>3.6</td>
<td>4.6
</td></tr></tbody></table>
<p>Ionization of acids is less in an acidic solvent than in water. For example, <a href="https://en.wikipedia.org/wiki/Hydrogen_chloride" title="Hydrogen chloride">hydrogen chloride</a> is a weak acid when dissolved in <a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">acetic acid</a>. This is because acetic acid is a much weaker base than water.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>HCl</mtext>
<mo>+</mo>
<msubsup>
<mtext>CH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>CO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>H</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msup>
<mtext>Cl</mtext>
<mrow>
<mo>−</mo>
</mrow>
</msup>
<mo>+</mo>
<msubsup>
<mtext>CH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>C</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<mtext>OH</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {HCl + CH3CO2H <=> Cl- + CH3C(OH)2+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0c192c824159eaefd6102eb6f8bd2b126379ce4a" style="height: 3.343ex; vertical-align: -1.005ex; width: 42.016ex;" /></span></dd><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mtext>acid</mtext>
</mrow>
<mo>+</mo>
<mrow>
<mtext>base </mtext>
</mrow>
<mrow>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
</mrow>
<mrow>
<mtext> conjugate base</mtext>
</mrow>
<mo>+</mo>
<mrow>
<mtext>conjugate acid</mtext>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\text{acid}}+{\text{base }}{\ce {<=>}}{\text{ conjugate base}}+{\text{conjugate acid}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/990a22f22c6c1ca62978ab86b2d7f8296a038fc8" style="height: 3.009ex; vertical-align: -0.671ex; width: 47.944ex;" /></span></dd></dl>
<p>Compare this reaction with what happens when acetic acid is dissolved in the more acidic solvent pure sulfuric acid:
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>SO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>CH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msubsup>
<mtext>CO</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>H</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
<msubsup>
<mtext>HSO</mtext>
<mrow>
<mn>4</mn>
</mrow>
<mrow>
<mo>−</mo>
</mrow>
</msubsup>
<mo>+</mo>
<msubsup>
<mtext>CH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>C</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<mtext>OH</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\ce {H2SO4 + CH3CO2H <=> HSO4- + CH3C(OH)2+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7a96118b0c5464bf40c77397817f581088b0a3da" style="height: 3.343ex; vertical-align: -1.005ex; width: 47.419ex;" /></span></dd></dl>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Carboxylic_acid_dimers.png"><img alt="This image illustrates how two carboxylic acids, C O O H, can associate through mutual hydrogen bonds. The hydroxyl portion O H of each molecule forms a hydrogen bond to the carbonyl portion C O of the other." class="mw-file-element" data-file-height="827" data-file-width="1803" height="64" src="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/Carboxylic_acid_dimers.png/140px-Carboxylic_acid_dimers.png" width="140" /></a><figcaption>Dimerization of a carboxylic acid.</figcaption></figure>
<p>The unlikely <a href="https://en.wikipedia.org/wiki/Diol" title="Diol">geminal diol</a> species <span class="chemf nowrap">CH<sub class="template-chem2-sub">3</sub>C(OH)<span class="template-chem2-su"><span>+</span><span>2</span></span></span> is stable in these environments. For aqueous solutions the <a href="https://en.wikipedia.org/wiki/PH" title="PH">pH</a> scale is the most convenient <a href="https://en.wikipedia.org/wiki/Acidity_function" title="Acidity function">acidity function</a>. Other acidity functions have been proposed for non-aqueous media, the most notable being the <a href="https://en.wikipedia.org/wiki/Hammett_acidity_function" title="Hammett acidity function">Hammett acidity function</a>, <i>H</i><sub>0</sub>, for <a href="https://en.wikipedia.org/wiki/Superacid" title="Superacid">superacid</a> media and its modified version <i>H</i><sub>−</sub> for <a href="https://en.wikipedia.org/wiki/Superbase" title="Superbase">superbasic</a> media.
</p><p>In aprotic solvents, <a href="https://en.wikipedia.org/wiki/Oligomer" title="Oligomer">oligomers</a>, such as the well-known acetic acid <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dimer_(chemistry)" title="Dimer (chemistry)">dimer</a>, may be formed by hydrogen bonding. An acid may also form hydrogen bonds to its conjugate base. This process, known as <a href="https://en.wikipedia.org/wiki/Homoassociation" title="Homoassociation">homoconjugation</a>, has the effect of enhancing the acidity of acids, lowering their effective p<i>K</i><sub>a</sub>
values, by stabilizing the conjugate base. Homoconjugation enhances the
proton-donating power of toluenesulfonic acid in acetonitrile solution
by a factor of nearly 800.
</p><p>In aqueous solutions, homoconjugation does not occur, because
water forms stronger hydrogen bonds to the conjugate base than does the
acid.
</p>
<h3><span class="mw-headline" id="Mixed_solvents">Mixed solvents</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Acetic_acid_pK_dioxane_water.png"><img alt="The p K A of acetic acid in the mixed solvent dioxane/water. p K A increases as the proportion of dioxane increases, primarily because the dielectric constant of the mixture decreases with increasing doxane content. A lower dielectric constant disfavors the dissociation of the uncharged acid into the charged ions, H + and C H 3 C O O minus, shifting the equilibrium to favor the uncharged protonated form C H 3 C O O H. Since the protonated form is the reactant not the product of the dissociation, this shift decreases the equilibrium constant K A, and increases P K A, its negative logarithm." class="mw-file-element" data-file-height="269" data-file-width="336" height="320" src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Acetic_acid_pK_dioxane_water.png/220px-Acetic_acid_pK_dioxane_water.png" width="400" /></a><figcaption>p<i>K</i><sub>a</sub> of acetic acid in dioxane/water mixtures. Data at 25 °C from Pine <i>et al.</i></figcaption></figure>
<p>When a compound has limited solubility in water it is common practice
(in the pharmaceutical industry, for example) to determine p<i>K</i><sub>a</sub> values in a solvent mixture such as water/<a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dioxane" title="Dioxane">dioxane</a> or water/<a href="https://en.wikipedia.org/wiki/Methanol" title="Methanol">methanol</a>, in which the compound is more soluble. In the example shown at the right, the p<i>K</i><sub>a</sub> value rises steeply with increasing percentage of dioxane as the dielectric constant of the mixture is decreasing.
</p><p>A p<i>K</i><sub>a</sub> value obtained in a mixed solvent cannot
be used directly for aqueous solutions. The reason for this is that when
the solvent is in its standard state its activity is <i>defined</i> as one. For example, the standard state of water:dioxane mixture with 9:1 <a href="https://en.wikipedia.org/wiki/Mixing_ratio" title="Mixing ratio">mixing ratio</a> is precisely that solvent mixture, with no added solutes. To obtain the p<i>K</i><sub>a</sub>
value for use with aqueous solutions it has to be extrapolated to zero
co-solvent concentration from values obtained from various co-solvent
mixtures.
</p><p>These facts are obscured by the omission of the solvent from the expression that is normally used to define p<i>K</i><sub>a</sub>, but p<i>K</i><sub>a</sub> values obtained in a <i>given</i> mixed solvent can be compared to each other, giving relative acid strengths. The same is true of p<i>K</i><sub>a</sub> values obtained in a particular non-aqueous solvent such a DMSO.
</p><p>A universal, solvent-independent, scale for acid dissociation
constants has not been developed, since there is no known way to compare
the standard states of two different solvents.
</p>
<h2><span class="mw-headline" id="Factors_that_affect_pKa_values">Factors that affect p<i>K</i><sub>a</sub> values</span></h2><p>Pauling's second rule is that the value of the first p<i>K</i><sub>a</sub> for acids of the formula XO<sub><i>m</i></sub>(OH)<sub><i>n</i></sub> depends primarily on the number of oxo groups <i>m</i>, and is approximately independent of the number of hydroxy groups <i>n</i>, and also of the central atom X. Approximate values of p<i>K</i><sub>a</sub> are 8 for <i>m</i> = 0, 2 for <i>m</i> = 1, −3 for <i>m</i> = 2 and < −10 for <i>m</i> = 3. Alternatively, various numerical formulas have been proposed including p<i>K</i><sub>a</sub> = 8 − 5<i>m</i> (known as <a href="https://en.wikipedia.org/wiki/Ronnie_Bell" title="Ronnie Bell">Bell's</a> rule), p<i>K</i><sub>a</sub> = 7 − 5<i>m</i>,<sup> </sup>or p<i>K</i><sub>a</sub> = 9 − 7<i>m</i>. The dependence on <i>m</i> correlates with the oxidation state of the central atom, X: the higher the oxidation state the stronger the oxyacid.
</p><p>For example, p<i>K</i><sub>a</sub> for HClO is 7.2, for HClO<sub>2</sub> is 2.0, for HClO<sub>3</sub> is −1 and HClO<sub>4</sub> is a strong acid (<span class="nowrap">p<i>K</i><sub>a</sub> ≪ 0</span>).
The increased acidity on adding an oxo group is due to stabilization of
the conjugate base by delocalization of its negative charge over an
additional oxygen atom. This rule can help assign molecular structure: for example, <a href="https://en.wikipedia.org/wiki/Phosphorous_acid" title="Phosphorous acid">phosphorous acid</a>, having <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Molecular_formula" title="Molecular formula">molecular formula</a> H<sub>3</sub>PO<sub>3</sub>, has a p<i>K</i><sub>a</sub> near 2, which suggested that the structure is HPO(OH)<sub>2</sub>, as later confirmed by <a href="https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_spectroscopy" title="Nuclear magnetic resonance spectroscopy">NMR spectroscopy</a>, and not P(OH)<sub>3</sub>, which would be expected to have a p<i>K</i><sub>a</sub> near 8.
</p>
<figure><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Chloroacetic_pka.png"><img class="mw-file-element" data-file-height="554" data-file-width="1504" height="111" src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Chloroacetic_pka.png/300px-Chloroacetic_pka.png" width="300" /></a><figcaption>pKa values for acetic, chloroacetic, dichloroacetic and trichloroacetic acids.</figcaption></figure>
<p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Inductive_effects" title="Inductive effects">Inductive effects</a> and <a href="https://en.wikipedia.org/wiki/Mesomeric_effect" title="Mesomeric effect">mesomeric effects</a> affect the p<i>K</i><sub>a</sub>
values. A simple example is provided by the effect of replacing the
hydrogen atoms in acetic acid by the more electronegative chlorine atom.
The electron-withdrawing effect of the substituent makes ionisation
easier, so successive p<i>K</i><sub>a</sub> values decrease in the series 4.7, 2.8, 1.4, and 0.7 when 0, 1, 2, or 3 chlorine atoms are present. The <a href="https://en.wikipedia.org/wiki/Hammett_equation" title="Hammett equation">Hammett equation</a>, provides a general expression for the effect of substituents.
</p>
<dl><dd>log(<i>K</i><sub>a</sub>) = log(<i>K</i><span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">0</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">a</sub></span>) + ρσ.</dd></dl>
<p><i>K</i><sub>a</sub> is the dissociation constant of a substituted compound, <i>K</i><span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">0</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">a</sub></span>
is the dissociation constant when the substituent is hydrogen, ρ is a
property of the unsubstituted compound and σ has a particular value for
each substituent. A plot of log(<i>K</i><sub>a</sub>) against σ is a straight line with <a href="https://en.wikipedia.org/wiki/Y-intercept" title="Y-intercept">intercept</a> log(<i>K</i><span style="display: inline-block; font-size: 80%; line-height: 1.2em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">0</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">a</sub></span>) and <a href="https://en.wikipedia.org/wiki/Slope" title="Slope">slope</a> ρ. This is an example of a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Linear_free_energy_relationship" title="Linear free energy relationship">linear free energy relationship</a> as log(<i>K</i><sub>a</sub>) is proportional to the standard free energy change. Hammett originally formulated the relationship with data from <a href="https://en.wikipedia.org/wiki/Benzoic_acid" title="Benzoic acid">benzoic acid</a> with different substituents in the <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arene_substitution_patterns" title="Arene substitution patterns">ortho</a>-</i> and <i><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Arene_substitution_patterns" title="Arene substitution patterns">para</a>-</i> positions: some numerical values are in <a href="https://en.wikipedia.org/wiki/Hammett_equation" title="Hammett equation">Hammett equation</a>. This and other studies allowed substituents to be ordered according to their <a href="https://en.wikipedia.org/wiki/Inductive_effect" title="Inductive effect">electron-withdrawing</a> or <a href="https://en.wikipedia.org/wiki/Inductive_effect" title="Inductive effect">electron-releasing</a> power, and to distinguish between inductive and mesomeric effects.
</p><p><a href="https://en.wikipedia.org/wiki/Alcohol_(chemistry)" title="Alcohol (chemistry)">Alcohols</a>
do not normally behave as acids in water, but the presence of a double
bond adjacent to the OH group can substantially decrease the p<i>K</i><sub>a</sub> by the mechanism of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Keto%E2%80%93enol_tautomerism" title="Keto–enol tautomerism">keto–enol tautomerism</a>. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Ascorbic_acid" title="Ascorbic acid">Ascorbic acid</a> is an example of this effect. The diketone 2,4-pentanedione (<a href="https://en.wikipedia.org/wiki/Acetylacetone" title="Acetylacetone">acetylacetone</a>) is also a weak acid because of the keto–enol equilibrium. In aromatic compounds, such as <a href="https://en.wikipedia.org/wiki/Phenol" title="Phenol">phenol</a>, which have an OH substituent, <a href="https://en.wikipedia.org/wiki/Conjugated_system" title="Conjugated system">conjugation</a> with the aromatic ring as a whole greatly increases the stability of the deprotonated form.
</p>
<div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="max-width: 204px; width: 204px;"><div class="trow"><div class="tsingle" style="max-width: 202px; width: 202px;"><div class="thumbimage"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Fumaric-acid-2D-skeletal.png"><img alt="" class="mw-file-element" data-file-height="627" data-file-width="1100" height="228" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Fumaric-acid-2D-skeletal.png/200px-Fumaric-acid-2D-skeletal.png" width="400" /></a></span></div><div class="thumbcaption"><a href="https://en.wikipedia.org/wiki/Fumaric_acid" title="Fumaric acid">Fumaric acid</a></div><div class="thumbcaption"> </div></div></div><div class="trow"><div class="tsingle" style="max-width: 202px; width: 202px;"><div class="thumbimage"><span><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Maleic-acid-2D-skeletal-A.svg"><img alt="" class="mw-file-element" data-file-height="58" data-file-width="141" height="164" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Maleic-acid-2D-skeletal-A.svg/200px-Maleic-acid-2D-skeletal-A.svg.png" width="400" /></a></span></div><div class="thumbcaption"><a href="https://en.wikipedia.org/wiki/Maleic_acid" title="Maleic acid">Maleic acid</a></div></div></div></div></div>
<p>Structural effects can also be important. The difference between <a href="https://en.wikipedia.org/wiki/Fumaric_acid" title="Fumaric acid">fumaric acid</a> and <a href="https://en.wikipedia.org/wiki/Maleic_acid" title="Maleic acid">maleic acid</a> is a classic example. Fumaric acid is (E)-1,4-but-2-enedioic acid, a <i>trans</i> <a href="https://en.wikipedia.org/wiki/Isomer" title="Isomer">isomer</a>, whereas maleic acid is the corresponding <i>cis</i> isomer, i.e. (Z)-1,4-but-2-enedioic acid (see <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cis-trans_isomerism" title="Cis-trans isomerism">cis-trans isomerism</a>). Fumaric acid has p<i>K</i><sub>a</sub> values of approximately 3.0 and 4.5. By contrast, maleic acid has p<i>K</i><sub>a</sub> values of approximately 1.5 and 6.5. The reason for this large difference is that when one proton is removed from the <i>cis</i> isomer (maleic acid) a strong <a href="https://en.wikipedia.org/wiki/Intramolecular_force" title="Intramolecular force">intramolecular</a> <a href="https://en.wikipedia.org/wiki/Hydrogen_bond" title="Hydrogen bond">hydrogen bond</a> is formed with the nearby remaining carboxyl group. This favors the formation of the maleate H<sup>+</sup>, and it opposes the removal of the second proton from that species. In the <i>trans</i> isomer, the two carboxyl groups are always far apart, so hydrogen bonding is not observed.
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Proton_sponge.svg"><img alt="Proton sponge is a derivative of naphthalene with dimethylamino groups in the one and ten positions. This brings the two dimethyl amino groups into close proximity to each other." class="mw-file-element" data-file-height="110" data-file-width="109" height="400" src="https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Proton_sponge.svg/140px-Proton_sponge.svg.png" width="397" /></a><figcaption>Proton sponge</figcaption></figure>
<p><a class="mw-redirect" href="https://en.wikipedia.org/wiki/Proton_sponge" title="Proton sponge">Proton sponge</a>, 1,8-bis(dimethylamino)naphthalene, has a p<i>K</i><sub>a</sub>
value of 12.1. It is one of the strongest amine bases known. The high
basicity is attributed to the relief of strain upon protonation and
strong internal hydrogen bonding.
</p><p>Effects of the solvent and solvation should be mentioned also in
this section. It turns out, these influences are more subtle than that
of a dielectric medium mentioned above. For example, the expected (by
electronic effects of methyl substituents) and observed in gas phase
order of basicity of methylamines, Me<sub>3</sub>N > Me<sub>2</sub>NH > MeNH<sub>2</sub> > NH<sub>3</sub>, is changed by water to Me<sub>2</sub>NH > MeNH<sub>2</sub> > Me<sub>3</sub>N > NH<sub>3</sub>.
Neutral methylamine molecules are hydrogen-bonded to water molecules
mainly through one acceptor, N–HOH, interaction and only occasionally
just one more donor bond, NH–OH<sub>2</sub>. Hence, methylamines are
stabilized to about the same extent by hydration, regardless of the
number of methyl groups. In stark contrast, corresponding methylammonium
cations always utilize <b>all</b> the available protons for donor NH–OH<sub>2</sub>
bonding. Relative stabilization of methylammonium ions thus decreases
with the number of methyl groups explaining the order of water basicity
of methylamines.
</p>
<h3><span class="mw-headline" id="Thermodynamics">Thermodynamics</span></h3><p>An equilibrium constant is related to the standard <a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" title="Gibbs free energy">Gibbs energy</a> change for the reaction, so for an acid dissociation constant
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>G</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mo>=</mo>
<mo>−</mo>
<mi>R</mi>
<mi>T</mi>
<mi>ln</mi>
<mo></mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>≈</mo>
<mn>2.303</mn>
<mi>R</mi>
<mi>T</mi>
<mtext> </mtext>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G^{\ominus }=-RT\ln K_{\text{a}}\approx 2.303RT\ \mathrm {p} K_{\text{a}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2e252e008b85a08583ba5de80e5c707a56f329e2" style="height: 2.843ex; vertical-align: -0.671ex; width: 36.017ex;" /></span>.</dd></dl>
<p><i>R</i> is the <a href="https://en.wikipedia.org/wiki/Gas_constant" title="Gas constant">gas constant</a> and <i>T</i> is the <a href="https://en.wikipedia.org/wiki/Kelvin" title="Kelvin">absolute temperature</a>. Note that <span class="nowrap">p<i>K</i><sub>a</sub> = −log(<i>K</i><sub>a</sub>)</span> and <span class="nowrap">2.303 ≈ <a href="https://en.wikipedia.org/wiki/Natural_logarithm" title="Natural logarithm">ln</a>(10)</span>. At 25 °C, Δ<i>G</i><sup>⊖</sup> in kJ·mol<sup>−1</sup> ≈ 5.708 p<i>K</i><sub>a</sub> (1 kJ·mol<sup>−1</sup> = 1000 <a href="https://en.wikipedia.org/wiki/Joule" title="Joule">joules</a> per <a href="https://en.wikipedia.org/wiki/Mole_(unit)" title="Mole (unit)">mole</a>). Free energy is made up of an <a href="https://en.wikipedia.org/wiki/Enthalpy" title="Enthalpy">enthalpy</a> term and an <a href="https://en.wikipedia.org/wiki/Entropy" title="Entropy">entropy</a> term.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>G</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mo>=</mo>
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>H</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
<mo>−</mo>
<mi>T</mi>
<mi mathvariant="normal">Δ</mi>
<msup>
<mi>S</mi>
<mrow>
<mo>⊖</mo>
</mrow>
</msup>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \Delta G^{\ominus }=\Delta H^{\ominus }-T\Delta S^{\ominus }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/194eb2a3019d9939637b559b24f5a8464a50ef73" style="height: 2.676ex; vertical-align: -0.505ex; width: 23.367ex;" /></span></dd></dl>
<p>The standard enthalpy change can be determined by <a href="https://en.wikipedia.org/wiki/Calorimetry" title="Calorimetry">calorimetry</a> or by using the <a href="https://en.wikipedia.org/wiki/Van_%27t_Hoff_equation" title="Van 't Hoff equation">van 't Hoff equation</a>,
though the calorimetric method is preferable. When both the standard
enthalpy change and acid dissociation constant have been determined, the
standard entropy change is easily calculated from the equation above.
In the following table, the entropy terms are calculated from the
experimental values of p<i>K</i><sub>a</sub> and Δ<i>H</i><sup>⊖</sup>. The data were critically selected and refer to 25 °C and zero ionic strength, in water.
</p>
<table class="wikitable" style="text-align: center;">
<caption>Acids
</caption>
<tbody><tr>
<th>Compound
</th>
<th>Equilibrium
</th>
<th>p<i>K</i><sub>a</sub>
</th>
<th>Δ<i>G</i><sup>⊖</sup> (kJ·mol<sup>−1</sup>)
</th>
<th>Δ<i>H</i><sup>⊖</sup> (kJ·mol<sup>−1</sup>)
</th>
<th>−<i>T</i>Δ<i>S</i><sup>⊖</sup> (kJ·mol<sup>−1</sup>)
</th></tr>
<tr>
<td style="text-align: left;">HA = <a href="https://en.wikipedia.org/wiki/Acetic_acid" title="Acetic acid">Acetic acid</a>
</td>
<td style="text-align: left;">HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>4.756
</td>
<td>27.147
</td>
<td>−0.41
</td>
<td>27.56
</td></tr>
<tr>
<td style="text-align: left;">H<sub>2</sub>A<sup>+</sup> = <a href="https://en.wikipedia.org/wiki/Glycine" title="Glycine">Glycine</a>H<sup>+</sup>
</td>
<td style="text-align: left;">H<sub>2</sub>A<sup>+</sup> ⇌ HA + H<sup>+</sup>
</td>
<td>2.351
</td>
<td>13.420
</td>
<td>4.00
</td>
<td>9.419
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>9.78
</td>
<td>55.825
</td>
<td>44.20
</td>
<td>11.6
</td></tr>
<tr>
<td style="text-align: left;">H<sub>2</sub>A = <a href="https://en.wikipedia.org/wiki/Maleic_acid" title="Maleic acid">Maleic acid</a>
</td>
<td style="text-align: left;">H<sub>2</sub>A ⇌ HA<sup>−</sup> + H<sup>+</sup>
</td>
<td>1.92
</td>
<td>10.76
</td>
<td>1.10
</td>
<td>9.85
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">HA<sup>−</sup> ⇌ H<sup>+</sup> + A<sup>2−</sup>
</td>
<td>6.27
</td>
<td>35.79
</td>
<td>−3.60
</td>
<td>39.4
</td></tr>
<tr>
<td style="text-align: left;">H<sub>3</sub>A = <a href="https://en.wikipedia.org/wiki/Citric_acid" title="Citric acid">Citric acid</a>
</td>
<td style="text-align: left;">H<sub>3</sub>A ⇌ H<sub>2</sub>A<sup>−</sup> + H<sup>+</sup>
</td>
<td>3.128
</td>
<td>17.855
</td>
<td>4.07
</td>
<td>13.78
</td></tr>
<tr>
<td>
<br /></td>
<td style="text-align: left;">H<sub>2</sub>A<sup>−</sup> ⇌ HA<sup>2−</sup> + H<sup>+</sup>
</td>
<td>4.76
</td>
<td>27.176
</td>
<td>2.23
</td>
<td>24.9
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">HA<sup>2−</sup> ⇌ A<sup>3−</sup> + H<sup>+</sup>
</td>
<td>6.40
</td>
<td>36.509
</td>
<td>−3.38
</td>
<td>39.9
</td></tr>
<tr>
<td style="text-align: left;">H<sub>3</sub>A = <a href="https://en.wikipedia.org/wiki/Boric_acid" title="Boric acid">Boric acid</a>
</td>
<td style="text-align: left;">H<sub>3</sub>A ⇌ H<sub>2</sub>A<sup>−</sup> + H<sup>+</sup>
</td>
<td>9.237
</td>
<td>52.725
</td>
<td>13.80
</td>
<td>38.92
</td></tr>
<tr>
<td style="text-align: left;">H<sub>3</sub>A = <a href="https://en.wikipedia.org/wiki/Phosphoric_acid" title="Phosphoric acid">Phosphoric acid</a>
</td>
<td style="text-align: left;">H<sub>3</sub>A ⇌ H<sub>2</sub>A<sup>−</sup> + H<sup>+</sup>
</td>
<td>2.148
</td>
<td>12.261
</td>
<td>−8.00
</td>
<td>20.26
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">H<sub>2</sub>A<sup>−</sup> ⇌ HA<sup>2−</sup> + H<sup>+</sup>
</td>
<td>7.20
</td>
<td>41.087
</td>
<td>3.60
</td>
<td>37.5
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">HA<sup>2−</sup> ⇌ A<sup>3−</sup> + H<sup>+</sup>
</td>
<td>12.35
</td>
<td>80.49
</td>
<td>16.00
</td>
<td>54.49
</td></tr>
<tr>
<td style="text-align: left;">HA<sup>−</sup> = <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Bisulfate" title="Bisulfate">Hydrogen sulfate</a>
</td>
<td style="text-align: left;">HA<sup>−</sup> ⇌ A<sup>2−</sup> + H<sup>+</sup>
</td>
<td>1.99
</td>
<td>11.36
</td>
<td>−22.40
</td>
<td>33.74
</td></tr>
<tr>
<td style="text-align: left;">H<sub>2</sub>A = <a href="https://en.wikipedia.org/wiki/Oxalic_acid" title="Oxalic acid">Oxalic acid</a>
</td>
<td style="text-align: left;">H<sub>2</sub>A ⇌ HA<sup>−</sup> + H<sup>+</sup>
</td>
<td>1.27
</td>
<td>7.27
</td>
<td>−3.90
</td>
<td>11.15
</td></tr>
<tr>
<td style="text-align: left;">
<br /></td>
<td style="text-align: left;">HA<sup>−</sup> ⇌ A<sup>2−</sup> + H<sup>+</sup>
</td>
<td>4.266
</td>
<td>24.351
</td>
<td>−7.00
</td>
<td>31.35
</td></tr></tbody></table>
<div class="mw-content-ltr mw-parser-output" dir="ltr" lang="en"><li id="cite_note-1"> <span class="reference-text">The hydrogen ion does not exist as such in solution. It combines with a solvent molecule; when the solvent is water a <a href="https://en.wikipedia.org/wiki/Hydronium" title="Hydronium">hydronium</a> ion is formed: <span class="chemf nowrap">H<sup class="template-chem2-sup">+</sup> + H<sub class="template-chem2-sub">2</sub>O → H<sub class="template-chem2-sub">3</sub>O<sup class="template-chem2-sup">+</sup></span>. This reaction is quantitative and hence can be ignored in the context of chemical equilibrium.</span>
</li>
<li id="cite_note-3"><br /></li><li id="cite_note-3"> <span class="reference-text">It is common practice to quote p<i>K</i> values rather than <i>K</i> values. <span class="nowrap">p<i>K</i> = −log<sub>10</sub> <i>K</i></span>. p<i>K</i><sub>a</sub> is often referred to as an acid dissociation constant, but this is, strictly speaking, incorrect as p<i>K</i><sub>a</sub> is the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Cologarithm" title="Cologarithm">cologarithm</a> of the dissociation constant.</span>
</li>
<li id="cite_note-4"><br /></li><li id="cite_note-4"> <span class="reference-text">It is implicit in this definition that the quotient of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Activity_coefficients" title="Activity coefficients">activity coefficients</a>, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mfrac>
<msub>
<mi>γ</mi>
<mrow>
<mi>A</mi>
<mi>H</mi>
</mrow>
</msub>
<mrow>
<msub>
<mi>γ</mi>
<mrow>
<msup>
<mi>A</mi>
<mrow>
<mo>−</mo>
</mrow>
</msup>
</mrow>
</msub>
<msub>
<mi>γ</mi>
<mrow>
<msup>
<mi>H</mi>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</msub>
</mrow>
</mfrac>
</mrow>
<mo>,</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle {\frac {\gamma _{AH}}{\gamma _{A^{-}}\gamma _{H^{+}}}},}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4949816a7eeea3bcd9c700190adbb4af2270af0d" style="height: 5.509ex; vertical-align: -2.505ex; width: 9.48ex;" /></span> is a constant with a value of 1 under a given set of experimental conditions.</span>
</li>
<li id="cite_note-60"><br /></li><li id="cite_note-60"> <span class="reference-text"><span class="nowrap">Δ<i>G</i><sup>⊖</sup> ≈ 2.303<i>RT</i>p<i>K</i><sub>a</sub></span></span>
</li>
<li id="cite_note-61"><br /></li><div class="reflist reflist-lower-alpha"><div class="mw-references-wrap"><ol class="references"><li id="cite_note-61" value="5"> <span class="reference-text">Computed here, from Δ<i>H</i> and Δ<i>G</i> values supplied in the citation, using <span class="nowrap">−<i>T</i>Δ<i>S</i><sup>⊖</sup> = Δ<i>G</i><sup>⊖</sup> − Δ<i>H</i><sup>⊖</sup></span></span>
</li></ol></div></div>
<table class="wikitable">
<caption>Conjugate acids of bases
</caption>
<tbody><tr>
<th>Compound
</th>
<th>Equilibrium
</th>
<th>p<i>K</i><sub>a</sub>
</th>
<th>ΔH<sup>⊖</sup> (kJ·mol<sup>−1</sup>)
</th>
<th>−<i>T</i>Δ<i>S</i><sup>⊖</sup> (kJ·mol<sup>−1</sup>)
</th></tr>
<tr>
<td style="text-align: left;">B = <a href="https://en.wikipedia.org/wiki/Ammonia" title="Ammonia">Ammonia</a>
</td>
<td style="text-align: left;">HB<sup>+</sup> ⇌ B + H<sup>+</sup>
</td>
<td>9.245
</td>
<td>51.95
</td>
<td>0.8205
</td></tr>
<tr>
<td style="text-align: left;">B = <a href="https://en.wikipedia.org/wiki/Methylamine" title="Methylamine">Methylamine</a>
</td>
<td style="text-align: left;">HB<sup>+</sup> ⇌ B + H<sup>+</sup>
</td>
<td>10.645
</td>
<td>55.34
</td>
<td>5.422
</td></tr>
<tr>
<td style="text-align: left;">B = <a href="https://en.wikipedia.org/wiki/Triethylamine" title="Triethylamine">Triethylamine</a>
</td>
<td style="text-align: left;">HB<sup>+</sup> ⇌ B + H<sup>+</sup>
</td>
<td>10.72
</td>
<td>43.13
</td>
<td>18.06
</td></tr></tbody></table>
<p>The first point to note is that, when p<i>K</i><sub>a</sub> is positive, the standard free energy change for the dissociation reaction is also positive. Second, some reactions are <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Exothermic" title="Exothermic">exothermic</a> and some are <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Endothermic" title="Endothermic">endothermic</a>, but, when Δ<i>H</i><sup>⊖</sup> is negative <i>T</i>ΔS<sup>⊖</sup> is the dominant factor, which determines that Δ<i>G</i><sup>⊖</sup> is positive. Last, the entropy contribution is always unfavourable (<span class="nowrap">Δ<i>S</i><sup>⊖</sup> < 0</span>)
in these reactions. Ions in aqueous solution tend to orient the
surrounding water molecules, which orders the solution and decreases the
entropy. The contribution of an ion to the entropy is the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Partial_molar_quantity" title="Partial molar quantity">partial molar</a> entropy which is often negative, especially for small or highly charged ions. The ionization of a neutral acid involves formation of two ions so that the entropy decreases (<span class="nowrap">Δ<i>S</i><sup>⊖</sup> < 0</span>).
On the second ionization of the same acid, there are now three ions and
the anion has a charge, so the entropy again decreases.
</p><p>Note that the <i>standard</i> free energy change for the reaction is for the changes <i>from</i> the reactants in their standard states <i>to</i> the products in their standard states. The free energy change <i>at</i> equilibrium is zero since the <a href="https://en.wikipedia.org/wiki/Chemical_potential" title="Chemical potential">chemical potentials</a> of reactants and products are equal at equilibrium.
</p>
<h2><span class="mw-headline" id="Experimental_determination">Experimental determination</span></h2><div class="hatnote navigation-not-searchable" role="note">See also: <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants" title="Determination of equilibrium constants">Determination of equilibrium constants</a></div>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Oxalic_acid_titration_grid.png"><img alt="The image shows the titration curve of oxalic acid, showing the pH of the solution as a function of added base. There is a small inflection point at about pH 3 and then a large jump from pH 5 to pH 11, followed by another region of slowly increasing pH." class="mw-file-element" data-file-height="600" data-file-width="800" height="300" src="https://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Oxalic_acid_titration_grid.png/220px-Oxalic_acid_titration_grid.png" width="400" /></a><figcaption>A calculated <a href="https://en.wikipedia.org/wiki/Titration_curve" title="Titration curve">titration curve</a> of <a href="https://en.wikipedia.org/wiki/Oxalic_acid" title="Oxalic acid">oxalic acid</a> titrated with a solution of <a href="https://en.wikipedia.org/wiki/Sodium_hydroxide" title="Sodium hydroxide">sodium hydroxide</a></figcaption></figure>
<p>The experimental determination of p<i>K</i><sub>a</sub> values is commonly performed by means of <a href="https://en.wikipedia.org/wiki/Titration" title="Titration">titrations</a>, in a medium of high ionic strength and at constant temperature.
A typical procedure would be as follows. A solution of the compound in
the medium is acidified with a strong acid to the point where the
compound is fully protonated. The solution is then titrated with a
strong base until all the protons have been removed. At each point in
the titration pH is measured using a <a href="https://en.wikipedia.org/wiki/Glass_electrode" title="Glass electrode">glass electrode</a> and a <a href="https://en.wikipedia.org/wiki/PH_meter" title="PH meter">pH meter</a>. The equilibrium constants are found by fitting calculated pH values to the observed values, using the method of <a href="https://en.wikipedia.org/wiki/Least_squares" title="Least squares">least squares</a>.
</p><p>The total volume of added strong base should be small compared to
the initial volume of titrand solution in order to keep the ionic
strength nearly constant. This will ensure that p<i>K</i><sub>a</sub> remains invariant during the titration.
</p><p>A calculated <a href="https://en.wikipedia.org/wiki/Titration_curve" title="Titration curve">titration curve</a> for oxalic acid is shown at the right. Oxalic acid has p<i>K</i><sub>a</sub>
values of 1.27 and 4.27. Therefore, the buffer regions will be centered
at about pH 1.3 and pH 4.3. The buffer regions carry the information
necessary to get the p<i>K</i><sub>a</sub> values as the concentrations of acid and conjugate base change along a buffer region.
</p><p>Between the two buffer regions there is an end-point, or <a href="https://en.wikipedia.org/wiki/Equivalence_point" title="Equivalence point">equivalence point</a>, at about pH 3. This end-point is not sharp and is typical of a diprotic acid whose buffer regions overlap by a small amount: p<i>K</i><sub>a2</sub> − p<i>K</i><sub>a1</sub> is about three in this example. (If the difference in p<i>K</i>
values were about two or less, the end-point would not be noticeable.)
The second end-point begins at about pH 6.3 and is sharp. This indicates
that all the protons have been removed. When this is so, the solution
is not buffered and the pH rises steeply on addition of a small amount
of strong base. However, the pH does not continue to rise indefinitely. A
new buffer region begins at about pH 11 (p<i>K</i><sub>w</sub> − 3), which is where <a href="https://en.wikipedia.org/wiki/Self-ionization_of_water" title="Self-ionization of water">self-ionization of water</a> becomes important.
</p><p>It is very difficult to measure pH values of less than two in aqueous solution with a <a href="https://en.wikipedia.org/wiki/Glass_electrode#Range_of_a_pH_glass_electrode" title="Glass electrode">glass electrode</a>, because the <a href="https://en.wikipedia.org/wiki/Nernst_equation" title="Nernst equation">Nernst equation</a> breaks down at such low pH values. To determine p<i>K</i> values of less than about 2 or more than about 11 <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants#Absorbance" title="Determination of equilibrium constants">spectrophotometric</a> or <a href="https://en.wikipedia.org/wiki/Determination_of_equilibrium_constants#NMR_chemical_shift_measurements" title="Determination of equilibrium constants">NMR</a> measurements may be used instead of, or combined with, pH measurements.
</p><p>When the glass electrode cannot be employed, as with non-aqueous solutions, spectrophotometric methods are frequently used. These may involve <a href="https://en.wikipedia.org/wiki/Absorbance" title="Absorbance">absorbance</a> or <a href="https://en.wikipedia.org/wiki/Fluorescence" title="Fluorescence">fluorescence</a>
measurements. In both cases the measured quantity is assumed to be
proportional to the sum of contributions from each photo-active species;
with absorbance measurements the <a href="https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law" title="Beer–Lambert law">Beer–Lambert law</a> is assumed to apply.
</p><p><a href="https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry" title="Isothermal titration calorimetry">Isothermal titration calorimetry</a> (ITC) may be used to determine both a p<i>K</i> value and the corresponding standard enthalpy for acid dissociation. Software to perform the calculations is supplied by the instrument manufacturers for simple systems.
</p><p>Aqueous solutions with normal water cannot be used for <sup>1</sup>H NMR measurements but <a href="https://en.wikipedia.org/wiki/Heavy_water" title="Heavy water">heavy water</a>, <span class="chemf nowrap">D<sub class="template-chem2-sub">2</sub>O</span>, must be used instead. <sup>13</sup>C NMR data, however, can be used with normal water and <sup>1</sup>H NMR spectra can be used with non-aqueous media. The quantities measured with NMR are time-averaged <a href="https://en.wikipedia.org/wiki/Chemical_shift" title="Chemical shift">chemical shifts</a>, as proton exchange is fast on the NMR time-scale. Other chemical shifts, such as those of <sup>31</sup>P can be measured.
</p>
<h3><span class="mw-headline" id="Micro-constants">Micro-constants</span></h3><figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:L-Cystein_-_L-Cysteine.svg"><img class="mw-file-element" data-file-height="121" data-file-width="185" height="262" src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/L-Cystein_-_L-Cysteine.svg/220px-L-Cystein_-_L-Cysteine.svg.png" width="400" /></a><figcaption>Cysteine</figcaption></figure>
<p>For some polyprotic acids, dissociation (or association) occurs at more than one nonequivalent site, and the observed macroscopic equilibrium constant, or macro-constant, is a combination of <a href="https://en.wikipedia.org/wiki/Equilibrium_constant#Micro-constants" title="Equilibrium constant">microconstants</a>
involving distinct species. When one reactant forms two products in
parallel, the macro-constant is a sum of two micro-constants, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>K</mi>
<mo>=</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>X</mi>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>K</mi>
<mrow>
<mi>Y</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K=K_{X}+K_{Y}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/fe74f2fb8784acef0b11ecd2d8bcc59747ae6406" style="height: 2.509ex; vertical-align: -0.671ex; width: 15.716ex;" /></span> This is true for example for the deprotonation of the <a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acid</a> <a href="https://en.wikipedia.org/wiki/Cysteine" title="Cysteine">cysteine</a>, which exists in solution as a neutral <a href="https://en.wikipedia.org/wiki/Zwitterion" title="Zwitterion">zwitterion</a> <span class="chemf nowrap">HS−CH<sub class="template-chem2-sub">2</sub>−CH(NH<span class="template-chem2-su"><span>+</span><span>3</span></span>)−COO<sup class="template-chem2-sup">−</sup></span>.
The two micro-constants represent deprotonation either at sulphur or at
nitrogen, and the macro-constant sum here is the acid dissociation
constant <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<mtext>SH</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>+</mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\mathrm {a} }=K_{\mathrm {a} }{\ce {(-SH)}}+K_{\mathrm {a} }{\ce {(-NH3+)}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2117f4e3b14155165bf72cbfdc7168e15c54b9f5" style="height: 3.176ex; vertical-align: -1.005ex; width: 30.935ex;" /></span>
</p>
<figure class="mw-default-size"><a class="mw-file-description" href="https://en.wikipedia.org/wiki/File:Spermine.svg"><img alt="Spermine is a long, symmetrical molecule capped at both ends with amino groups N H 2. It has two N H groups symmetrically placed within the molecule, separated from each other by four methylene groups C H 2, and from the amino ends by three methylene groups. Thus, the full molecular formula is N H 2 C H 2 C H 2 C H 2 N H C H 2 C H 2 C H 2 C H 2 N H C H 2 C H 2 C H 2 N H 2." class="mw-file-element" data-file-height="85" data-file-width="420" height="82" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Spermine.svg/220px-Spermine.svg.png" width="400" /></a><figcaption>Spermine</figcaption></figure>
<p>Similarly, a base such as <a href="https://en.wikipedia.org/wiki/Spermine" title="Spermine">spermine</a> has more than one site where protonation can occur. For example, mono-protonation can occur at a terminal <span class="chemf nowrap">−NH<sub class="template-chem2-sub">2</sub></span> group or at internal <span class="chemf nowrap">−NH−</span> groups. The <i>K</i><sub>b</sub> values for dissociation of spermine protonated at one or other of the sites are examples of <a href="https://en.wikipedia.org/wiki/Equilibrium_constant#Micro-constants" title="Equilibrium constant">micro-constants</a>. They cannot be determined directly by means of pH, absorbance, fluorescence or NMR measurements; a measured <i>K</i><sub>b</sub> value is the sum of the K values for the micro-reactions.
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mtext>b</mtext>
</mrow>
</msub>
<mo>=</mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>terminal</mtext>
</mrow>
</msub>
<mo>+</mo>
<msub>
<mi>K</mi>
<mrow>
<mtext>internal</mtext>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\text{b}}=K_{\text{terminal}}+K_{\text{internal}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a291f7c25b57809d2a945d0b41edd51cd8b57559" style="height: 2.509ex; vertical-align: -0.671ex; width: 25.082ex;" /></span></dd></dl>
<p>Nevertheless, the site of protonation is very important for
biological function, so mathematical methods have been developed for the
determination of micro-constants.
</p><p>When two reactants form a single product in parallel, the macro-constant <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<mi>K</mi>
<mo>=</mo>
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mi>X</mi>
</mrow>
</msub>
<mo>+</mo>
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mi>Y</mi>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle 1/K=1/K_{X}+1/K_{Y}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b1ed5f763332cfcb2b66f5fd461e32223870d3b6" style="height: 2.843ex; vertical-align: -0.838ex; width: 22.691ex;" /></span> For example, the abovementioned equilibrium for spermine may be considered in terms of <i>K</i><sub>a</sub> values of two <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Tautomeric" title="Tautomeric">tautomeric</a> conjugate acids, with macro-constant In this case <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mtext>a</mtext>
</mrow>
</msub>
<mo>=</mo>
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>a</mtext>
</mrow>
<mo>,</mo>
<mrow>
<mtext>terminal</mtext>
</mrow>
</mrow>
</msub>
<mo>+</mo>
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mtext>a</mtext>
</mrow>
<mo>,</mo>
<mrow>
<mtext>internal</mtext>
</mrow>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle 1/K_{\text{a}}=1/K_{{\text{a}},{\text{terminal}}}+1/K_{{\text{a}},{\text{internal}}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/95519899c59d7a51472dd72c0f3172185bf047e4" style="height: 3.009ex; vertical-align: -1.005ex; width: 35.17ex;" /></span> This is equivalent to the preceding expression since <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">b</mi>
</mrow>
</mrow>
</msub>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K_{\mathrm {b} }}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cb4b0d1248046e29abad2b81e6e0f7063628b4aa" style="height: 2.509ex; vertical-align: -0.671ex; width: 3.119ex;" /></span> is proportional to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mn>1</mn>
<mrow>
<mo>/</mo>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle 1/K_{\mathrm {a} }.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b6a40ae77d2868c30c59727c9a6b67f2ecfa84c0" style="height: 2.843ex; vertical-align: -0.838ex; width: 5.999ex;" /></span>
</p><p>When a reactant undergoes two reactions in series, the
macro-constant for the combined reaction is the product of the
microconstant for the two steps. For example, the abovementioned
cysteine zwitterion can lose two protons, one from sulphur and one from
nitrogen, and the overall macro-constant for losing two protons is the
product of two dissociation constants <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mi>K</mi>
<mo>=</mo>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<mtext>SH</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle K=K_{\mathrm {a} }{\ce {(-SH)}}K_{\mathrm {a} }{\ce {(-NH3+)}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5c2d2c84506b439456422d9326bef6d525267951" style="height: 3.176ex; vertical-align: -1.005ex; width: 27.133ex;" /></span> This can also be written in terms of logarithmic constants as <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<mi>K</mi>
<mo>=</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<mtext>SH</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>+</mo>
<mrow>
<mi mathvariant="normal">p</mi>
</mrow>
<msub>
<mi>K</mi>
<mrow>
<mrow>
<mi mathvariant="normal">a</mi>
</mrow>
</mrow>
</msub>
<mrow>
<mrow>
<mo stretchy="false">(</mo>
<mrow>
<mo>−</mo>
</mrow>
<msubsup>
<mtext>NH</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mo>+</mo>
</mrow>
</msubsup>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mo>.</mo>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle \mathrm {p} K=\mathrm {p} K_{\mathrm {a} }{\ce {(-SH)}}+\mathrm {p} K_{\mathrm {a} }{\ce {(-NH3+)}}.}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e81b946fbe01f333793556b4a320acd88d361bc7" style="height: 3.176ex; vertical-align: -1.005ex; width: 33.851ex;" /></span>
</p>
<h2><span class="mw-headline" id="Applications_and_significance">Applications and significance</span></h2><p>A knowledge of p<i>K</i><sub>a</sub>
values is important for the quantitative treatment of systems involving
acid–base equilibria in solution. Many applications exist in <a href="https://en.wikipedia.org/wiki/Biochemistry" title="Biochemistry">biochemistry</a>; for example, the p<i>K</i><sub>a</sub> values of proteins and <a href="https://en.wikipedia.org/wiki/Amino_acid" title="Amino acid">amino acid</a> side chains are of major importance for the activity of enzymes and the stability of proteins. <a href="https://en.wikipedia.org/wiki/Protein_pKa_calculations" title="Protein pKa calculations">Protein p<i>K</i><sub>a</sub> values</a> cannot always be measured directly, but may be calculated using theoretical methods. <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Buffer_solutions" title="Buffer solutions">Buffer solutions</a> are used extensively to provide solutions at or near the physiological pH for the study of biochemical reactions; the design of these solutions depends on a knowledge of the p<i>K</i><sub>a</sub> values of their components. Important buffer solutions include <a href="https://en.wikipedia.org/wiki/MOPS" title="MOPS">MOPS</a>, which provides a solution with pH 7.2, and <a href="https://en.wikipedia.org/wiki/Tricine" title="Tricine">tricine</a>, which is used in <a href="https://en.wikipedia.org/wiki/Gel_electrophoresis" title="Gel electrophoresis">gel electrophoresis</a>. Buffering is an essential part of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Acid_base_physiology" title="Acid base physiology">acid base physiology</a> including <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis" title="Acid–base homeostasis">acid–base homeostasis</a>, and is key to understanding disorders such as <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_disorder" title="Acid–base disorder">acid–base disorder</a>. The <a href="https://en.wikipedia.org/wiki/Isoelectric_point" title="Isoelectric point">isoelectric point</a> of a given molecule is a function of its p<i>K</i> values, so different molecules have different isoelectric points. This permits a technique called <a href="https://en.wikipedia.org/wiki/Isoelectric_focusing" title="Isoelectric focusing">isoelectric focusing</a>, which is used for separation of proteins by <a href="https://en.wikipedia.org/wiki/Two-dimensional_gel_electrophoresis" title="Two-dimensional gel electrophoresis">2-D gel polyacrylamide gel electrophoresis</a>.
</p><p>Buffer solutions also play a key role in <a href="https://en.wikipedia.org/wiki/Analytical_chemistry" title="Analytical chemistry">analytical chemistry</a>.
They are used whenever there is a need to fix the pH of a solution at a
particular value. Compared with an aqueous solution, the pH of a buffer
solution is relatively insensitive to the addition of a small amount of
strong acid or strong base. The buffer capacity of a simple buffer solution is largest when pH = p<i>K</i><sub>a</sub>. In <a href="https://en.wikipedia.org/wiki/Acid%E2%80%93base_extraction" title="Acid–base extraction">acid–base extraction</a>, the efficiency of extraction of a compound into an organic phase, such as an <a href="https://en.wikipedia.org/wiki/Ether" title="Ether">ether</a>,
can be optimised by adjusting the pH of the aqueous phase using an
appropriate buffer. At the optimum pH, the concentration of the
electrically neutral species is maximised; such a species is more
soluble in organic solvents having a low <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Dielectric_constant" title="Dielectric constant">dielectric constant</a> than it is in water. This technique is used for the purification of weak acids and bases.
</p><p>A <a href="https://en.wikipedia.org/wiki/PH_indicator" title="PH indicator">pH indicator</a> is a weak acid or weak base that changes colour in the transition pH range, which is approximately p<i>K</i><sub>a</sub> ± 1. The design of a <a href="https://en.wikipedia.org/wiki/Universal_indicator" title="Universal indicator">universal indicator</a> requires a mixture of indicators whose adjacent p<i>K</i><sub>a</sub> values differ by about two, so that their transition pH ranges just overlap.
</p><p>In <a href="https://en.wikipedia.org/wiki/Pharmacology" title="Pharmacology">pharmacology</a>, ionization of a compound alters its physical behaviour and macro properties such as solubility and <a href="https://en.wikipedia.org/wiki/Partition_coefficient" title="Partition coefficient">lipophilicity</a>, log <i>p</i>).
For example, ionization of any compound will increase the solubility in
water, but decrease the lipophilicity. This is exploited in <a href="https://en.wikipedia.org/wiki/Drug_development" title="Drug development">drug development</a> to increase the concentration of a compound in the blood by adjusting the p<i>K</i><sub>a</sub> of an ionizable group.
</p><p>Knowledge of p<i>K</i><sub>a</sub> values is important for the understanding of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Complex_(chemistry)" title="Complex (chemistry)">coordination complexes</a>, which are formed by the interaction of a metal ion, M<sup>m+</sup>, acting as a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lewis_acid" title="Lewis acid">Lewis acid</a>, with a <a href="https://en.wikipedia.org/wiki/Ligand" title="Ligand">ligand</a>, L, acting as a <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Lewis_base" title="Lewis base">Lewis base</a>.
However, the ligand may also undergo protonation reactions, so the
formation of a complex in aqueous solution could be represented
symbolically by the reaction
</p>
<dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML">
<semantics>
<mrow>
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">[</mo>
<mrow>
<mtext>M</mtext>
<msubsup>
<mrow>
<mo stretchy="false">(</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mo stretchy="false">)</mo>
</mrow>
<mrow>
<mrow>
<mtext mathvariant="italic">n</mtext>
</mrow>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mi>m</mi>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<mrow>
<mtext>LH</mtext>
<mrow>
<mover>
<mrow>
<mrow>
<mpadded depth="0" height="0">
<mrow>
<mo stretchy="false">↽</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo>−</mo>
</mrow>
</mpadded>
</mrow>
</mrow>
<mrow>
<mstyle displaystyle="false" scriptlevel="0">
<mrow>
<mrow>
<mo>−</mo>
</mrow>
<mspace width="negativethinmathspace"></mspace>
<mspace width="negativethinmathspace"></mspace>
<mrow>
<mo stretchy="false">⇀</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
</mover>
</mrow>
</mrow>
<mtext> </mtext>
<mo stretchy="false">[</mo>
<msub>
<mrow>
<mtext>M</mtext>
<mrow>
<mo stretchy="false">(</mo>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>2</mn>
</mrow>
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<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<mtext>O</mtext>
<mo stretchy="false">)</mo>
</mrow>
</mrow>
<mrow>
<mi>n</mi>
<mo>−</mo>
<mn>1</mn>
</mrow>
</msub>
<mrow>
<mtext>L</mtext>
</mrow>
<msup>
<mo stretchy="false">]</mo>
<mrow>
<mo stretchy="false">(</mo>
<mi>m</mi>
<mo>−</mo>
<mn>1</mn>
<mo stretchy="false">)</mo>
<mo>+</mo>
</mrow>
</msup>
<mo>+</mo>
<mrow>
<msubsup>
<mtext>H</mtext>
<mrow>
<mn>3</mn>
</mrow>
<mrow>
<mspace depth=".2em" height="0pt" width="0pt"></mspace>
</mrow>
</msubsup>
<msup>
<mtext>O</mtext>
<mrow>
<mo>+</mo>
</mrow>
</msup>
</mrow>
</mstyle>
</mrow>
</semantics>
</math></span><img alt="{\displaystyle [{\ce {M(H2O)_{\mathit {n}}}}]^{m+}+{\ce {LH<=>}}\ [{\ce {M(H2O)}}_{n-1}{\ce {L}}]^{(m-1)+}+{\ce {H3O+}}}" aria-hidden="true" class="mwe-math-fallback-image-inline mw-invert" src="https://wikimedia.org/api/rest_v1/media/math/render/svg/696ff04eb241a2f6a358b8dd1b9c373ea3a8c91d" style="height: 3.676ex; vertical-align: -1.171ex; width: 54.47ex;" /></span></dd></dl>
<p>To determine the equilibrium constant for this reaction, in which the ligand loses a proton, the p<i>K</i><sub>a</sub> of the protonated ligand must be known. In practice, the ligand may be polyprotic; for example <a class="mw-redirect" href="https://en.wikipedia.org/wiki/EDTA" title="EDTA">EDTA</a><sup>4−</sup> can accept four protons; in that case, all p<i>K</i><sub>a</sub> values must be known. In addition, the metal ion is subject to <a href="https://en.wikipedia.org/wiki/Hydrolysis#Hydrolysis_of_metal_aqua_ions" title="Hydrolysis">hydrolysis</a>, that is, it behaves as a weak acid, so the p<i>K</i> values for the hydrolysis reactions must also be known.
</p><p>Assessing the <a href="https://en.wikipedia.org/wiki/Risk_assessment" title="Risk assessment">hazard</a> associated with an acid or base may require a knowledge of p<i>K</i><sub>a</sub> values. For example, <a href="https://en.wikipedia.org/wiki/Hydrogen_cyanide" title="Hydrogen cyanide">hydrogen cyanide</a> is a very toxic gas, because the <a href="https://en.wikipedia.org/wiki/Cyanide#Toxicity" title="Cyanide">cyanide ion</a> inhibits the iron-containing enzyme <a href="https://en.wikipedia.org/wiki/Cytochrome_c_oxidase" title="Cytochrome c oxidase">cytochrome c oxidase</a>. Hydrogen cyanide is a weak acid in aqueous solution with a p<i>K</i><sub>a</sub>
of about 9. In strongly alkaline solutions, above pH 11, say, it
follows that sodium cyanide is "fully dissociated" so the hazard due to
the hydrogen cyanide gas is much reduced. An acidic solution, on the
other hand, is very hazardous because all the cyanide is in its acid
form. Ingestion of cyanide by mouth is potentially fatal, independently
of pH, because of the reaction with cytochrome c oxidase.
</p><p>In <a href="https://en.wikipedia.org/wiki/Environmental_science" title="Environmental science">environmental science</a> acid–base equilibria are important for lakes and rivers;<sup> </sup>for example, <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Humic_acid" title="Humic acid">humic acids</a> are important components of natural waters. Another example occurs in <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Chemical_oceanography" title="Chemical oceanography">chemical oceanography</a>: in order to quantify the solubility of iron(III) in seawater at various <a href="https://en.wikipedia.org/wiki/Salinity" title="Salinity">salinities</a>, the p<i>K</i><sub>a</sub> values for the formation of the iron(III) hydrolysis products <span class="chemf nowrap">Fe(OH)<sup>2+</sup></span>, <span class="chemf nowrap">Fe(OH)<span class="template-chem2-su"><span>+</span><span>2</span></span></span> and <span class="chemf nowrap">Fe(OH)<sub class="template-chem2-sub">3</sub></span> were determined, along with the <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Solubility_product" title="Solubility product">solubility product</a> of <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Iron_hydroxide" title="Iron hydroxide">iron hydroxide</a>.
</p>
<h2><span class="mw-headline" id="Values_for_common_substances">Values for common substances</span></h2><p>There are multiple techniques to determine the p<i>K</i><sub>a</sub>
of a chemical, leading to some discrepancies between different sources.
Well measured values are typically within 0.1 units of each other. Data
presented here were taken at 25 °C in water. More values can be found in the <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#Thermodynamics">Thermodynamics</a> section, above. A table of p<i>K</i><sub>a</sub> of carbon acids, measured in DMSO, can be found on the page on <a href="https://en.wikipedia.org/wiki/Carbanion" title="Carbanion">carbanions</a>.
</p>
<table class="wikitable sortable jquery-tablesorter">
<thead><tr>
<th class="unsortable">Chemical
</th>
<th class="unsortable">Equilibrium
</th>
<th class="headerSort" role="columnheader button" tabindex="0" title="Sort ascending">p<i>K</i><sub>a</sub>
</th></tr></thead><tbody>
<tr>
<td rowspan="2">BH = <a href="https://en.wikipedia.org/wiki/Adenine" title="Adenine">Adenine</a>
</td>
<td>BH ⇌ B<sup>−</sup> + H<sup>+</sup>
</td>
<td>4.17
</td></tr>
<tr>
<td><span class="chemf nowrap">BH<span style="display: inline-block; font-size: 80%; line-height: 1em; margin-bottom: -0.3em; text-align: left; vertical-align: -0.4em;"><sup style="font-size: inherit; line-height: inherit; vertical-align: baseline;">+</sup><br /><sub style="font-size: inherit; line-height: inherit; vertical-align: baseline;">2</sub></span></span> ⇌ BH + H<sup>+</sup>
</td>
<td>9.65
</td></tr>
<tr>
<td rowspan="3">H<sub>3</sub>A = <a href="https://en.wikipedia.org/wiki/Arsenic_acid" title="Arsenic acid">Arsenic acid</a>
</td>
<td>H<sub>3</sub>A ⇌ H<sub>2</sub>A<sup>−</sup> + H<sup>+</sup>
</td>
<td>2.22
</td></tr>
<tr>
<td>H<sub>2</sub>A<sup>−</sup> ⇌ HA<sup>2−</sup> + H<sup>+</sup>
</td>
<td>6.98
</td></tr>
<tr>
<td>HA<sup>2−</sup> ⇌ A<sup>3−</sup> + H<sup>+</sup>
</td>
<td>11.53
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Benzoic_acid" title="Benzoic acid">Benzoic acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>4.204
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Butyric_acid" title="Butyric acid">Butyric acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>4.82
</td></tr>
<tr>
<td rowspan="2">H<sub>2</sub>A = <a href="https://en.wikipedia.org/wiki/Chromic_acid" title="Chromic acid">Chromic acid</a>
</td>
<td>H<sub>2</sub>A ⇌ HA<sup>−</sup> + H<sup>+</sup>
</td>
<td>0.98
</td></tr>
<tr>
<td>HA<sup>−</sup> ⇌ A<sup>2−</sup> + H<sup>+</sup>
</td>
<td>6.5
</td></tr>
<tr>
<td>B = <a href="https://en.wikipedia.org/wiki/Codeine" title="Codeine">Codeine</a>
</td>
<td>BH<sup>+</sup> ⇌ B + H<sup>+</sup>
</td>
<td>8.17
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Cresol" title="Cresol">Cresol</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>10.29
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Formic_acid" title="Formic acid">Formic acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>3.751
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Hydrofluoric_acid" title="Hydrofluoric acid">Hydrofluoric acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>3.17
</td></tr>
<tr>
<td>HA = <a class="mw-redirect" href="https://en.wikipedia.org/wiki/Hydrocyanic_acid" title="Hydrocyanic acid">Hydrocyanic acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>9.21
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Hydrogen_selenide" title="Hydrogen selenide">Hydrogen selenide</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>3.89
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Hydrogen_peroxide" title="Hydrogen peroxide">Hydrogen peroxide</a> (90%)
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>11.7
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Lactic_acid" title="Lactic acid">Lactic acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>3.86
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Propionic_acid" title="Propionic acid">Propionic acid</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>4.87
</td></tr>
<tr>
<td>HA = <a href="https://en.wikipedia.org/wiki/Phenol" title="Phenol">Phenol</a>
</td>
<td>HA ⇌ H<sup>+</sup> + A<sup>−</sup>
</td>
<td>9.99
</td></tr>
<tr>
<td rowspan="2">H<sub>2</sub>A = <a href="https://en.wikipedia.org/wiki/Vitamin_C" title="Vitamin C"><small>L</small>-(+)-Ascorbic Acid</a>
</td>
<td>H<sub>2</sub>A ⇌ HA<sup>−</sup> + H<sup>+</sup>
</td>
<td>4.17
</td></tr>
<tr>
<td>HA<sup>−</sup> ⇌ A<sup>2−</sup> + H<sup>+</sup>
</td>
<td>11.57
</td></tr></tbody></table></div>David J Strumfelshttp://www.blogger.com/profile/09219454080416178949noreply@blogger.com