Nitrous oxide

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Nitrous oxide

Names
IUPAC names Nitrous oxide (not recommended) Dinitrogen oxide (alternative name)
Systematic IUPAC name Oxodiazen-2-ium-1-ide
Other names Laughing gas, sweet air, nitrous, nos, protoxide of nitrogen, hyponitrous oxide, dinitrogen oxide, dinitrogen monoxide
Identifiers
CAS Number	10024-97-2
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	8137358
ChEBI	CHEBI:17045
ChEMBL	ChEMBL1234579
ChemSpider	923
DrugBank	DB06690
ECHA InfoCard	100.030.017
E number	E942 (glazing agents, ...)
Gmelin Reference	2153410
KEGG	D00102
PubChem CID	948
RTECS number	QX1350000
UNII	K50XQU1029
UN number	1070 (compressed) 2201 (liquid)
CompTox Dashboard (EPA)	DTXSID8021066

InChI

SMILES
Properties
Chemical formula	N 2O
Molar mass	44.013 g/mol
Appearance	colourless gas
Density	1.977 g/L (gas)
Melting point	−90.86 °C (−131.55 °F; 182.29 K)
Boiling point	−88.48 °C (−127.26 °F; 184.67 K)
Solubility in water	1.5 g/L (15 °C)
Solubility	soluble in alcohol, ether, sulfuric acid
log P	0.35
Vapor pressure	5150 kPa (20 °C)
Magnetic susceptibility (χ)	−18.9·10−6 cm3/mol
Refractive index (nD)	1.000516 (0 °C, 101,325 kPa)
Viscosity	14.90 μPa·s
Structure
Molecular shape	linear, C∞v
Dipole moment	0.166 D
Thermochemistry
Std molar entropy (S⦵298)	219.96 J/(K·mol)
Std enthalpy of formation (ΔfH⦵298)	+82.05 kJ/mol
Pharmacology
ATC code	N01AX13 (WHO)
Routes of administration	Inhalation
Pharmacokinetics:
Metabolism	0.004%
Biological half-life	5 minutes
Excretion	Respiratory
Hazards
GHS labelling:
Pictograms
NFPA 704 (fire diamond)	2 0 0 OX
Flash point	Nonflammable
Safety data sheet (SDS)	Ilo.org, ICSC 0067
Related compounds
Related nitrogen oxides	Nitric oxide Dinitrogen trioxide Nitrogen dioxide Dinitrogen tetroxide Dinitrogen pentoxide
Related compounds	Ammonium nitrate Azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  verify (what is  ?) Infobox references

Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula N
₂O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects. Its colloquial name, "laughing gas", coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is on the World Health Organization's List of Essential Medicines. It is also used as an oxidiser in rocket propellants, and in motor racing to increase the power output of engines.

Nitrous oxide's atmospheric concentration reached 333 parts per billion (ppb) in 2020, increasing at a rate of about 1 ppb annually. It is a major scavenger of stratospheric ozone, with an impact comparable to that of CFCs. Global accounting of N
₂O sources and sinks over the decade ending 2016 indicates that about 40% of the average 17 TgN/yr (teragrams of nitrogen per year) of emissions originated from human activity, and shows that emissions growth chiefly came from expanding agriculture and industry sources within emerging economies. Being the third most important long-lived greenhouse gas, nitrous oxide also substantially contributes to global warming.

Nitrous oxide is used as a propellant, and has a variety of applications from rocketry to making whipped cream. It is used as a recreational drug for its potential to induce a brief "high"; most recreational users are unaware of its neurotoxicity and potential to cause neurological damage.

Uses

Rocket motors

Nitrous oxide may be used as an oxidiser in a rocket motor. It has advantages over other oxidisers in that it is much less toxic, and because of its stability at room temperature it is also easier to store and relatively safe to carry on a flight. As a secondary benefit, it may be decomposed readily to form breathing air. Its high density and low storage pressure (when maintained at low temperature) enable it to be highly competitive with stored high-pressure gas systems.

In a 1914 patent, American rocket pioneer Robert Goddard suggested nitrous oxide and gasoline as possible propellants for a liquid-fuelled rocket. Nitrous oxide has been the oxidiser of choice in several hybrid rocket designs (using solid fuel with a liquid or gaseous oxidiser). The combination of nitrous oxide with hydroxyl-terminated polybutadiene fuel has been used by SpaceShipOne and others. It also is notably used in amateur and high power rocketry with various plastics as the fuel.

Nitrous oxide also may be used in a monopropellant rocket. In the presence of a heated catalyst, N
₂O will decompose exothermically into nitrogen and oxygen, at a temperature of approximately 1,070 °F (577 °C). Because of the large heat release, the catalytic action rapidly becomes secondary, as thermal autodecomposition becomes dominant. In a vacuum thruster, this may provide a monopropellant specific impulse (I_sp) of as much as 180 s. While noticeably less than the I_sp available from hydrazine thrusters (monopropellant or bipropellant with dinitrogen tetroxide), the decreased toxicity makes nitrous oxide an option worth investigating.

Nitrous oxide is said to deflagrate at approximately 600 °C (1,112 °F) at a pressure of 309 psi (21 atmospheres). At 600 psi, for example, the required ignition energy is only 6 joules, whereas N
₂O at 130 psi a 2,500-joule ignition energy input is insufficient.

Internal combustion engine

Main article: Nitrous oxide engine

In vehicle racing, nitrous oxide (often referred to as just "nitrous") allows the engine to burn more fuel by providing more oxygen during combustion. The increase in oxygen allows for an increase in the injection of fuel, allowing the engine to produce more engine power. The gas is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures, about 570 degrees F (~300C). Therefore, it often is mixed with another fuel that is easier to deflagrate. Nitrous oxide is a strong oxidising agent, roughly equivalent to hydrogen peroxide, and much stronger than oxygen gas.

Nitrous oxide is stored as a compressed liquid; the evaporation and expansion of liquid nitrous oxide in the intake manifold causes a large drop in intake charge temperature, resulting in a denser charge, further allowing more air/fuel mixture to enter the cylinder. Sometimes nitrous oxide is injected into (or prior to) the intake manifold, whereas other systems directly inject, right before the cylinder (direct port injection) to increase power.

The technique was used during World War II by Luftwaffe aircraft with the GM-1 system to boost the power output of aircraft engines. Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to extremely high altitudes. Accordingly, it was only used by specialised planes such as high-altitude reconnaissance aircraft, high-speed bombers and high-altitude interceptor aircraft. It sometimes could be found on Luftwaffe aircraft also fitted with another engine-boost system, MW 50, a form of water injection for aviation engines that used methanol for its boost capabilities.

One of the major problems of using nitrous oxide in a reciprocating engine is that it can produce enough power to damage or destroy the engine. Very large power increases are possible, and if the mechanical structure of the engine is not properly reinforced, the engine may be severely damaged, or destroyed, during this kind of operation. It is very important with nitrous oxide augmentation of petrol engines to maintain proper operating temperatures and fuel levels to prevent "pre-ignition", or "detonation" (sometimes referred to as "knock"). Most problems that are associated with nitrous oxide do not come from mechanical failure due to the power increases. Since nitrous oxide allows a much denser charge into the cylinder, it dramatically increases cylinder pressures. The increased pressure and temperature can cause problems such as melting the piston or valves. It also may crack or warp the piston or head and cause pre-ignition due to uneven heating.

Automotive-grade liquid nitrous oxide differs slightly from medical-grade nitrous oxide. A small amount of sulfur dioxide (SO
₂) is added to prevent substance abuse.

Aerosol propellant

Food-grade N
₂O whipped-cream chargers

The gas is approved for use as a food additive (E number: E942), specifically as an aerosol spray propellant. Its most common uses in this context are in aerosol whipped cream canisters and cooking sprays.

The gas is extremely soluble in fatty compounds. In aerosol whipped cream, it is dissolved in the fatty cream until it leaves the can, when it becomes gaseous and thus creates foam. Used in this way, it produces whipped cream which is four times the volume of the liquid, whereas whipping air into cream only produces twice the volume. If air were used as a propellant, oxygen would accelerate rancidification of the butterfat, but nitrous oxide inhibits such degradation. Carbon dioxide cannot be used for whipped cream because it is acidic in water, which would curdle the cream and give it a seltzer-like "sparkling" sensation.

The whipped cream produced with nitrous oxide is unstable, and will return to a more liquid state within half an hour to one hour. Thus, the method is not suitable for decorating food that will not be served immediately.

During December 2016, some manufacturers reported a shortage of aerosol whipped creams in the United States due to an explosion at the Air Liquide nitrous oxide facility in Florida in late August. With a major facility offline, the disruption caused a shortage resulting in the company diverting the supply of nitrous oxide to medical clients rather than to food manufacturing. The shortage came during the Christmas and holiday season when canned whipped cream use is normally at its highest.

Similarly, cooking spray, which is made from various types of oils combined with lecithin (an emulsifier), may use nitrous oxide as a propellant. Other propellants used in cooking spray include food-grade alcohol and propane.

Medicine

Main article: Nitrous oxide (medication)

 

Medical-grade N
₂O tanks used in dentistry

Nitrous oxide has been used in dentistry and surgery, as an anaesthetic and analgesic, since 1844. In the early days, the gas was administered through simple inhalers consisting of a breathing bag made of rubber cloth. Today, the gas is administered in hospitals by means of an automated relative analgesia machine, with an anaesthetic vaporiser and a medical ventilator, that delivers a precisely dosed and breath-actuated flow of nitrous oxide mixed with oxygen in a 2:1 ratio.

Nitrous oxide is a weak general anaesthetic, and so is generally not used alone in general anaesthesia, but used as a carrier gas (mixed with oxygen) for more powerful general anaesthetic drugs such as sevoflurane or desflurane. It has a minimum alveolar concentration of 105% and a blood/gas partition coefficient of 0.46. The use of nitrous oxide in anaesthesia, however, can increase the risk of postoperative nausea and vomiting.

Dentists use a simpler machine which only delivers an N
₂O/O
₂ mixture for the patient to inhale while conscious. The patient is kept conscious throughout the procedure, and retains adequate mental faculties to respond to questions and instructions from the dentist.

Inhalation of nitrous oxide is used frequently to relieve pain associated with childbirth, trauma, oral surgery and acute coronary syndrome (includes heart attacks). Its use during labour has been shown to be a safe and effective aid for birthing women. Its use for acute coronary syndrome is of unknown benefit.

In Britain and Canada, Entonox and Nitronox are used commonly by ambulance crews (including unregistered practitioners) as rapid and highly effective analgesic gas.

Fifty percent nitrous oxide can be considered for use by trained non-professional first aid responders in prehospital settings, given the relative ease and safety of administering 50% nitrous oxide as an analgesic. The rapid reversibility of its effect would also prevent it from precluding diagnosis.

Recreational use

Main article: Recreational use of nitrous oxide

 

Aquatint depiction of a laughing gas party in the nineteenth century, by Thomas Rowlandson

 

Street sign indicating ban of nitrous oxide use near the Poelestraat in Groningen

 

Whippit remnants (the small steel canisters) of recreational drug use, the Netherlands, 2017

Recreational inhalation of nitrous oxide, with the purpose of causing euphoria and/or slight hallucinations, began as a phenomenon for the British upper class in 1799, known as "laughing gas parties".

Starting in the nineteenth century, widespread availability of the gas for medical and culinary purposes allowed the recreational use to expand greatly throughout the world. In the United Kingdom, as of 2014, nitrous oxide was estimated to be used by almost half a million young people at nightspots, festivals and parties.

Widespread recreational use of the drug throughout the UK was featured in the 2017 Vice documentary Inside The Laughing Gas Black Market, in which journalist Matt Shea met with dealers of the drug who stole it from hospitals.

A significant issue cited in London's press is the effect of nitrous oxide canister littering, which is highly visible and causes significant complaint from communities.

Recreational users often misperceive nitrous oxide as a route to a "safe high", and are unaware of its potential for causing neurological damage. In Australia, recreation use became a public health concern following a rise in reported cases of neurotoxicity and a rise in emergency room admissions, and in (the state of) South Australia legislation was passed in 2020 to restrict canister sales.

Safety

Nitrous oxide is a significant occupational hazard for surgeons, dentists and nurses. Because nitrous oxide is minimally metabolised in humans (with a rate of 0.004%), it retains its potency when exhaled into the room by the patient, and can pose an intoxicating and prolonged exposure hazard to the clinic staff if the room is poorly ventilated. Where nitrous oxide is administered, a continuous-flow fresh-air ventilation system or N
₂O scavenger system is used to prevent a waste-gas buildup.

The National Institute for Occupational Safety and Health recommends that workers' exposure to nitrous oxide should be controlled during the administration of anaesthetic gas in medical, dental and veterinary operators. It set a recommended exposure limit (REL) of 25 ppm (46 mg/m³) to escaped anaesthetic.

Mental and manual impairment

Exposure to nitrous oxide causes short-term decreases in mental performance, audiovisual ability and manual dexterity. These effects coupled with the induced spatial and temporal disorientation could result in physical harm to the user from environmental hazards.

Neurotoxicity and neuroprotection

Nitrous oxide is neurotoxic and long-term or habitual use can cause severe neurological damage.

Like other NMDA receptor antagonists, it has been suggested that N
₂O produces neurotoxicity in the form of Olney's lesions in rodents upon prolonged (several hour) exposure. New research has arisen suggesting that Olney's lesions do not occur in humans, however, and similar drugs such as ketamine are now believed not to be acutely neurotoxic. It has been argued that, because N
₂O is rapidly expelled from the body under normal circumstances, it is less likely to be neurotoxic than other NMDAR antagonists. Indeed, in rodents, short-term exposure results in only mild injury that is rapidly reversible, and neuronal death occurs only after constant and sustained exposure. Nitrous oxide also may cause neurotoxicity after extended exposure because of hypoxia. This is especially true of non-medical formulations such as whipped-cream chargers (also known as "whippets" or "nangs"), which never contain oxygen, since oxygen makes cream rancid.

In heavy (≥400 g or ≥200 L of N₂O gas in one session) or frequent (regular, e.g. daily or weekly) users reported to poison control centers, signs of peripheral neuropathy have been noted: the presence of ataxia (gait abnormalities) or paresthesia (perception of abnormal sensations, e.g. tingling, numbness, prickling, mostly in the extremities). These are considered an early sign of neurological damage and indicates chronic toxicity.

Nitrous oxide at 75% by volume reduces ischemia-induced neuronal death induced by occlusion of the middle cerebral artery in rodents, and decreases NMDA-induced Ca²⁺ influx in neuronal cell cultures, a critical event involved in excitotoxicity.

DNA damage

Occupational exposure to ambient nitrous oxide has been associated with DNA damage, due to interruptions in DNA synthesis. This correlation is dose-dependent and does not appear to extend to casual recreational use; however, further research is needed to confirm the duration and quantity of exposure needed to cause damage.

Oxygen deprivation

If pure nitrous oxide is inhaled without oxygen mixed in, this can eventually lead to oxygen deprivation resulting in loss of blood pressure, fainting and even heart attacks. This can occur if the user inhales large quantities continuously, as with a strap-on mask connected to a gas canister. It can also happen if the user engages in excessive breath-holding or uses any other inhalation system that cuts off a supply of fresh air. A further risk is that symptoms of frostbite can occur on the lips, larynx and bronchi if the gas is inhaled directly from the gas container. Therefore, nitrous oxide is often inhaled from condoms or balloons.

Vitamin B₁₂ deficiency

Long-term exposure to nitrous oxide may cause vitamin B₁₂ deficiency. This can cause serious neurotoxicity if the user has preexisting vitamin B₁₂ deficiency. It inactivates the cobalamin form of vitamin B₁₂ by oxidation. Symptoms of vitamin B₁₂ deficiency, including sensory neuropathy, myelopathy and encephalopathy, may occur within days or weeks of exposure to nitrous oxide anaesthesia in people with subclinical vitamin B₁₂ deficiency.

Symptoms are treated with high doses of vitamin B₁₂, but recovery can be slow and incomplete.

People with normal vitamin B₁₂ levels have stores to make the effects of nitrous oxide insignificant, unless exposure is repeated and prolonged (nitrous oxide abuse). Vitamin B₁₂ levels should be checked in people with risk factors for vitamin B₁₂ deficiency prior to using nitrous oxide anaesthesia.

Prenatal development

Several experimental studies in rats indicate that chronic exposure of pregnant females to nitrous oxide may have adverse effects on the developing fetus.

Chemical/physical risks

At room temperature (20 °C [68 °F]) the saturated vapour pressure is 50.525 bar, rising up to 72.45 bar at 36.4 °C (97.5 °F)—the critical temperature. The pressure curve is thus unusually sensitive to temperature.

As with many strong oxidisers, contamination of parts with fuels have been implicated in rocketry accidents, where small quantities of nitrous/fuel mixtures explode due to "water hammer"-like effects (sometimes called "dieseling"—heating due to adiabatic compression of gases can reach decomposition temperatures). Some common building materials such as stainless steel and aluminium can act as fuels with strong oxidisers such as nitrous oxide, as can contaminants that may ignite due to adiabatic compression.

There also have been incidents where nitrous oxide decomposition in plumbing has led to the explosion of large tanks.

Mechanism of action

The pharmacological mechanism of action of N
₂O in medicine is not fully known. However, it has been shown to directly modulate a broad range of ligand-gated ion channels, and this likely plays a major role in many of its effects. It moderately blocks NMDAR and β₂-subunit-containing nACh channels, weakly inhibits AMPA, kainate, GABA_C and 5-HT₃ receptors, and slightly potentiates GABA_A and glycine receptors. It also has been shown to activate two-pore-domain K⁺
channels. While N
₂O affects quite a few ion channels, its anaesthetic, hallucinogenic and euphoriant effects are likely caused predominantly, or fully, via inhibition of NMDA receptor-mediated currents. In addition to its effects on ion channels, N
₂O may act to imitate nitric oxide (NO) in the central nervous system, and this may be related to its analgesic and anxiolytic properties. Nitrous oxide is 30 to 40 times more soluble than nitrogen.

The effects of inhaling sub-anaesthetic doses of nitrous oxide have been known to vary, based on several factors, including settings and individual differences; however, from his discussion, Jay (2008) suggests that it has been reliably known to induce the following states and sensations:

• Intoxication
• Euphoria/dysphoria
• Spatial disorientation
• Temporal disorientation
• Reduced pain sensitivity

A minority of users also will present with uncontrolled vocalisations and muscular spasms. These effects generally disappear minutes after removal of the nitrous oxide source.

Anxiolytic effect

In behavioural tests of anxiety, a low dose of N
₂O is an effective anxiolytic, and this anti-anxiety effect is associated with enhanced activity of GABA_A receptors, as it is partially reversed by benzodiazepine receptor antagonists. Mirroring this, animals that have developed tolerance to the anxiolytic effects of benzodiazepines are partially tolerant to N
₂O. Indeed, in humans given 30% N
₂O, benzodiazepine receptor antagonists reduced the subjective reports of feeling "high", but did not alter psychomotor performance, in human clinical studies.

Analgesic effect

The analgesic effects of N
₂O are linked to the interaction between the endogenous opioid system and the descending noradrenergic system. When animals are given morphine chronically, they develop tolerance to its pain-killing effects, and this also renders the animals tolerant to the analgesic effects of N
₂O. Administration of antibodies that bind and block the activity of some endogenous opioids (not β-endorphin) also block the antinociceptive effects of N
₂O. Drugs that inhibit the breakdown of endogenous opioids also potentiate the antinociceptive effects of N
₂O. Several experiments have shown that opioid receptor antagonists applied directly to the brain block the antinociceptive effects of N
₂O, but these drugs have no effect when injected into the spinal cord.

Apart from an indirect action, nitrous oxide, like morphine  also interacts directly with the endogenous opioid system by binding at opioid receptor binding sites.

Conversely, α₂-adrenoceptor antagonists block the pain-reducing effects of N
₂O when given directly to the spinal cord, but not when applied directly to the brain. Indeed, α_2B-adrenoceptor knockout mice or animals depleted in norepinephrine are nearly completely resistant to the antinociceptive effects of N
₂O.^[81] Apparently N
₂O-induced release of endogenous opioids causes disinhibition of brainstem noradrenergic neurons, which release norepinephrine into the spinal cord and inhibit pain signalling. Exactly how N
₂O causes the release of endogenous opioid peptides remains uncertain.

Properties and reactions

Nitrous oxide is a colourless, non-toxic gas with a faint, sweet odour.

Nitrous oxide supports combustion by releasing the dipolar bonded oxygen radical, and can thus relight a glowing splint.

N
₂O is inert at room temperature and has few reactions. At elevated temperatures, its reactivity increases. For example, nitrous oxide reacts with NaNH
₂ at 460 K (187 °C) to give NaN
₃:

2 NaNH
₂ + N
₂O → NaN
₃ + NaOH + NH
₃

The above reaction is the route adopted by the commercial chemical industry to produce azide salts, which are used as detonators.

History

The gas was first synthesised in 1772 by English natural philosopher and chemist Joseph Priestley who called it dephlogisticated nitrous air (see phlogiston theory) or inflammable nitrous air. Priestley published his discovery in the book Experiments and Observations on Different Kinds of Air (1775), where he described how to produce the preparation of "nitrous air diminished", by heating iron filings dampened with nitric acid.

Early use

"Living Made Easy": A satirical print from 1830 depicting Humphry Davy administering a dose of laughing gas to a woman

The first important use of nitrous oxide was made possible by Thomas Beddoes and James Watt, who worked together to publish the book Considerations on the Medical Use and on the Production of Factitious Airs (1794). This book was important for two reasons. First, James Watt had invented a novel machine to produce "factitious airs" (including nitrous oxide) and a novel "breathing apparatus" to inhale the gas. Second, the book also presented the new medical theories by Thomas Beddoes, that tuberculosis and other lung diseases could be treated by inhalation of "Factitious Airs".

Sir Humphry Davy's Researches chemical and philosophical: chiefly concerning nitrous oxide (1800), pages 556 and 557 (right), outlining potential anaesthetic properties of nitrous oxide in relieving pain during surgery

The machine to produce "Factitious Airs" had three parts: a furnace to burn the needed material, a vessel with water where the produced gas passed through in a spiral pipe (for impurities to be "washed off"), and finally the gas cylinder with a gasometer where the gas produced, "air", could be tapped into portable air bags (made of airtight oily silk). The breathing apparatus consisted of one of the portable air bags connected with a tube to a mouthpiece. With this new equipment being engineered and produced by 1794, the way was paved for clinical trials, which began in 1798 when Thomas Beddoes established the "Pneumatic Institution for Relieving Diseases by Medical Airs" in Hotwells (Bristol). In the basement of the building, a large-scale machine was producing the gases under the supervision of a young Humphry Davy, who was encouraged to experiment with new gases for patients to inhale. The first important work of Davy was examination of the nitrous oxide, and the publication of his results in the book: Researches, Chemical and Philosophical (1800). In that publication, Davy notes the analgesic effect of nitrous oxide at page 465 and its potential to be used for surgical operations at page 556. Davy coined the name "laughing gas" for nitrous oxide.

Despite Davy's discovery that inhalation of nitrous oxide could relieve a conscious person from pain, another 44 years elapsed before doctors attempted to use it for anaesthesia. The use of nitrous oxide as a recreational drug at "laughing gas parties", primarily arranged for the British upper class, became an immediate success beginning in 1799. While the effects of the gas generally make the user appear stuporous, dreamy and sedated, some people also "get the giggles" in a state of euphoria, and frequently erupt in laughter.

One of the earliest commercial producers in the U.S. was George Poe, cousin of the poet Edgar Allan Poe, who also was the first to liquefy the gas.

Anaesthetic use

Further information: Nitrous oxide (medication)

The first time nitrous oxide was used as an anaesthetic drug in the treatment of a patient was when dentist Horace Wells, with assistance by Gardner Quincy Colton and John Mankey Riggs, demonstrated insensitivity to pain from a dental extraction on 11 December 1844. In the following weeks, Wells treated the first 12 to 15 patients with nitrous oxide in Hartford, Connecticut, and, according to his own record, only failed in two cases. In spite of these convincing results having been reported by Wells to the medical society in Boston in December 1844, this new method was not immediately adopted by other dentists. The reason for this was most likely that Wells, in January 1845 at his first public demonstration to the medical faculty in Boston, had been partly unsuccessful, leaving his colleagues doubtful regarding its efficacy and safety. The method did not come into general use until 1863, when Gardner Quincy Colton successfully started to use it in all his "Colton Dental Association" clinics, that he had just established in New Haven and New York City. Over the following three years, Colton and his associates successfully administered nitrous oxide to more than 25,000 patients. Today, nitrous oxide is used in dentistry as an anxiolytic, as an adjunct to local anaesthetic.

Nitrous oxide was not found to be a strong enough anaesthetic for use in major surgery in hospital settings, however. Instead, diethyl ether, being a stronger and more potent anaesthetic, was demonstrated and accepted for use in October 1846, along with chloroform in 1847. When Joseph Thomas Clover invented the "gas-ether inhaler" in 1876, however, it became a common practice at hospitals to initiate all anaesthetic treatments with a mild flow of nitrous oxide, and then gradually increase the anaesthesia with the stronger ether or chloroform. Clover's gas-ether inhaler was designed to supply the patient with nitrous oxide and ether at the same time, with the exact mixture being controlled by the operator of the device. It remained in use by many hospitals until the 1930s. Although hospitals today use a more advanced anaesthetic machine, these machines still use the same principle launched with Clover's gas-ether inhaler, to initiate the anaesthesia with nitrous oxide, before the administration of a more powerful anaesthetic.

As a patent medicine

Colton's popularisation of nitrous oxide led to its adoption by a number of less than reputable quacksalvers, who touted it as a cure for consumption, scrofula, catarrh and other diseases of the blood, throat and lungs. Nitrous oxide treatment was administered and licensed as a patent medicine by the likes of C. L. Blood and Jerome Harris in Boston and Charles E. Barney of Chicago.

Production

Reviewing various methods of producing nitrous oxide is published.

Industrial methods

Nitrous oxide production

Nitrous oxide is prepared on an industrial scale by careful heating of ammonium nitrate at about 250 °C, which decomposes into nitrous oxide and water vapour.

NH
₄NO
₃ → 2 H
₂O + N
₂O

The addition of various phosphate salts favours formation of a purer gas at slightly lower temperatures. This reaction may be difficult to control, resulting in detonation.

Laboratory methods

The decomposition of ammonium nitrate is also a common laboratory method for preparing the gas. Equivalently, it can be obtained by heating a mixture of sodium nitrate and ammonium sulfate:

2 NaNO
₃ + (NH
₄)₂SO
₄ → Na
₂SO
₄ + 2 N
₂O + 4 H
₂O

Another method involves the reaction of urea, nitric acid and sulfuric acid:

2 (NH₂)₂CO + 2 HNO
₃ + H
₂SO
₄ → 2 N
₂O + 2 CO
₂ + (NH₄)₂SO₄ + 2 H
₂O

Direct oxidation of ammonia with a manganese dioxide-bismuth oxide catalyst has been reported: cf. Ostwald process.

2 NH
₃ + 2 O
₂ → N
₂O + 3 H
₂O

Hydroxylammonium chloride reacts with sodium nitrite to give nitrous oxide. If the nitrite is added to the hydroxylamine solution, the only remaining by-product is salt water. If the hydroxylamine solution is added to the nitrite solution (nitrite is in excess), however, then toxic higher oxides of nitrogen also are formed:

NH
₃OHCl + NaNO
₂ → N
₂O + NaCl + 2 H
₂O

Treating HNO
₃ with SnCl
₂ and HCl also has been demonstrated:

2 HNO
₃ + 8 HCl + 4 SnCl
₂ → 5 H
₂O + 4 SnCl
₄ + N
₂O

Hyponitrous acid decomposes to N₂O and water with a half-life of 16 days at 25 °C at pH 1–3.

H₂N₂O₂→ H₂O + N₂O

Atmospheric occurrence

Nitrous oxide (N₂O) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-billion.

 

Nitrous oxide atmospheric concentration since 1978.

 

Annual growth rate of atmospheric nitrous oxide since 2000.

 

Earth's nitrous oxide budget from the Global Carbon Project (2020).

Nitrous oxide is a minor component of Earth's atmosphere and is an active part of the planetary nitrogen cycle. Based on analysis of air samples gathered from sites around the world, its concentration surpassed 330 ppb in 2017. The growth rate of about 1 ppb per year has also accelerated during recent decades. Nitrous oxide's atmospheric abundance has grown more than 20% from a base level of about 270 ppb in year 1750. Important atmospheric properties of N
₂O are summarized in the following table:

Property	Value
Ozone depletion potential (ODP)	0.17 (CCl3F = 1)
Global warming potential (GWP: 100-year)	265 (CO2 = 1)
Atmospheric lifetime	121 years

In October 2020 scientists published a comprehensive quantification of global N
₂O sources and sinks. They report that human-induced emissions increased by 30% over the past four decades and are the main cause of the increase in atmospheric concentration. The recent growth has exceeded some of the highest projected emission scenarios.

Emissions by source

As of 2010, it was estimated that about 29.5 million tonnes of N
₂O (containing 18.8 million tonnes of nitrogen) were entering the atmosphere each year; of which 64% were natural, and 36% due to human activity.

Most of the N
₂O emitted into the atmosphere, from natural and anthropogenic sources, is produced by microorganisms such as denitrifying bacteria and fungi in soils and oceans. Soils under natural vegetation are an important source of nitrous oxide, accounting for 60% of all naturally produced emissions. Other natural sources include the oceans (35%) and atmospheric chemical reactions (5%).

A 2019 study showed that emissions from thawing permafrost are 12 times higher than previously assumed.

The main components of anthropogenic emissions are fertilised agricultural soils and livestock manure (42%), runoff and leaching of fertilisers (25%), biomass burning (10%), fossil fuel combustion and industrial processes (10%), biological degradation of other nitrogen-containing atmospheric emissions (9%) and human sewage (5%). Agriculture enhances nitrous oxide production through soil cultivation, the use of nitrogen fertilisers and animal waste handling. These activities stimulate naturally occurring bacteria to produce more nitrous oxide. Nitrous oxide emissions from soil can be challenging to measure as they vary markedly over time and space, and the majority of a year's emissions may occur when conditions are favorable during "hot moments" and/or at favorable locations known as "hotspots".

Among industrial emissions, the production of nitric acid and adipic acid are the largest sources of nitrous oxide emissions. The adipic acid emissions specifically arise from the degradation of the nitrolic acid intermediate derived from nitration of cyclohexanone.

Biological processes

Natural processes that generate nitrous oxide may be classified as nitrification and denitrification. Specifically, they include:

• aerobic autotrophic nitrification, the stepwise oxidation of ammonia (NH
  ₃) to nitrite (NO⁻
  ₂) and to nitrate (NO⁻
  ₃)
• anaerobic heterotrophic denitrification, the stepwise reduction of NO⁻
  ₃ to NO⁻
  ₂, nitric oxide (NO), N
  ₂O and ultimately N
  ₂, where facultative anaerobe bacteria use NO⁻
  ₃ as an electron acceptor in the respiration of organic material in the condition of insufficient oxygen (O
  ₂)
• nitrifier denitrification, which is carried out by autotrophic NH
  ₃-oxidising bacteria and the pathway whereby ammonia (NH
  ₃) is oxidised to nitrite (NO⁻
  ₂), followed by the reduction of NO⁻
  ₂ to nitric oxide (NO), N
  ₂O and molecular nitrogen (N
  ₂)
• heterotrophic nitrification
• aerobic denitrification by the same heterotrophic nitrifiers
• fungal denitrification
• non-biological chemodenitrification

These processes are affected by soil chemical and physical properties such as the availability of mineral nitrogen and organic matter, acidity and soil type, as well as climate-related factors such as soil temperature and water content.

The emission of the gas to the atmosphere is limited greatly by its consumption inside the cells, by a process catalysed by the enzyme nitrous oxide reductase.

Environmental impact

Greenhouse effect

Trends in the atmospheric abundance of long-lived greenhouse gases

Nitrous oxide has significant global warming potential as a greenhouse gas. On a per-molecule basis, considered over a 100-year period, nitrous oxide has 265 times the atmospheric heat-trapping ability of carbon dioxide (CO
₂). However, because of its low concentration (less than 1/1,000 of that of CO
₂), its contribution to the greenhouse effect is less than one third that of carbon dioxide, and also less than water vapour and methane. On the other hand, since 38% or more of the N
₂O entering the atmosphere is the result of human activity, control of nitrous oxide is considered part of efforts to curb greenhouse gas emissions.

A 2008 study by Nobel Laureate Paul Crutzen suggests that the amount of nitrous oxide release attributable to agricultural nitrate fertilisers has been seriously underestimated, most of which presumably, would come under soil and oceanic release in the Environmental Protection Agency data. Nitrous oxide is released into the atmosphere through agriculture, when farmers add nitrogen-based fertilizers onto the fields, and through the breakdown of animal manure. Approximately 79 percent of all nitrous oxide released in the United States came from nitrogen fertilization. Reduction of emissions can be a hot topic in the politics of climate change.

Nitrous oxide is also released as a by-product of burning fossil fuel, though the amount released depends on which fuel was used. It is also emitted through the manufacture of nitric acid, which is used in the synthesis of nitrogen fertilizers. The production of adipic acid, a precursor to nylon and other synthetic clothing fibres, also releases nitrous oxide. The total amount of nitrous oxide released that is of human origins is about 40 percent.

Ozone layer depletion

Nitrous oxide has also been implicated in thinning the ozone layer. A 2009 study suggested that N
₂O emission was the single most important ozone-depleting emission and it was expected to remain the largest throughout the 21st century.

Legality

In the United States, possession of nitrous oxide is legal under federal law and is not subject to DEA purview. It is, however, regulated by the Food and Drug Administration under the Food Drug and Cosmetics Act; prosecution is possible under its "misbranding" clauses, prohibiting the sale or distribution of nitrous oxide for the purpose of human consumption. Many states have laws regulating the possession, sale and distribution of nitrous oxide. Such laws usually ban distribution to minors or limit the amount of nitrous oxide that may be sold without special license. For example, in the state of California, possession for recreational use is prohibited and qualifies as a misdemeanor.

In August 2015, the Council of the London Borough of Lambeth (UK) banned the use of the drug for recreational purposes, making offenders liable to an on-the-spot fine of up to £1,000.

In New Zealand, the Ministry of Health has warned that nitrous oxide is a prescription medicine, and its sale or possession without a prescription is an offense under the Medicines Act. This statement would seemingly prohibit all non-medicinal uses of nitrous oxide, although it is implied that only recreational use will be targeted legally.

In India, transfer of nitrous oxide from bulk cylinders to smaller, more transportable E-type, 1,590-litre-capacity tanks is legal when the intended use of the gas is for medical anaesthesia.

Laughter

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Laughter 

Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter can rise from such activities as being tickled, or from humorous stories or thoughts. Most commonly, it is considered an auditory expression of a number of positive emotional states, such as joy, mirth, happiness, or relief. On some occasions, however, it may be caused by contrary emotional states such as embarrassment, surprise, or confusion such as nervous laughter or courtesy laugh. Age, gender, education, language, and culture are all indicators as to whether a person will experience laughter in a given situation. Some other species of primate (chimpanzees, gorillas and orangutans) show laughter-like vocalizations in response to physical contact such as wrestling, play chasing or tickling.

Laughter is a part of human behavior regulated by the brain, helping humans clarify their intentions in social interaction and providing an emotional context to conversations. Laughter is used as a signal for being part of a group—it signals acceptance and positive interactions with others. Laughter is sometimes seen as contagious, and the laughter of one person can itself provoke laughter from others as a positive feedback.

The study of humor and laughter, and its psychological and physiological effects on the human body, is called gelotology.

Nature

Laughter might be thought of as an audible expression or appearance of excitement, an inward feeling of joy and happiness. It may ensue from jokes, tickling, and other stimuli completely unrelated to psychological state, such as nitrous oxide. One group of researchers speculated that noises from infants as early as 16 days old may be vocal laughing sounds or laughter. However, the weight of the evidence supports the appearance of such sounds at 15 weeks to four months of age.

Laughter researcher Robert Provine [es] said: "Laughter is a mechanism everyone has; laughter is part of universal human vocabulary. There are thousands of languages, hundreds of thousands of dialects, but everyone speaks laughter in pretty much the same way." Babies have the ability to laugh before they ever speak. Children who are born blind and deaf still retain the ability to laugh.

Provine argues that "Laughter is primitive, an unconscious vocalization." Provine argues that it probably is genetic. In a study of the "Giggle Twins", two happy twins who were separated at birth and only reunited 43 years later, Provine reports that "until they met each other, neither of these exceptionally happy ladies had known anyone who laughed as much as they did." They reported this even though they had been brought together by their adoptive parents, who they indicated were "undemonstrative and dour". He indicates that the twins "inherited some aspects of their laugh sound and pattern, readiness to laugh, and maybe even taste in humor".

Scientists have noted the similarity in forms of laughter induced by tickling among various primates, which suggests that laughter derives from a common origin among primate species.

The spotted hyena, another species of animal, was also known as the laughing hyena because of the way it sounds like when it communicates.

A very rare neurological condition has been observed whereby the sufferer is unable to laugh out loud, a condition known as aphonogelia.

Brain

A woman laughing

 

A man laughing

Neurophysiology indicates that laughter is linked with the activation of the ventromedial prefrontal cortex, that produces endorphins. Scientists have shown that parts of the limbic system are involved in laughter. This system is involved in emotions and helps us with functions necessary for humans' survival. The structures in the limbic system that are involved in laughter are the hippocampus and the amygdala.

The December 7, 1984, Journal of the American Medical Association describes the neurological causes of laughter as follows:

"Although there is no known 'laugh center' in the brain, its neural mechanism has been the subject of much, albeit inconclusive, speculation. It is evident that its expression depends on neural paths arising in close association with the telencephalic and diencephalic centers concerned with respiration. Wilson considered the mechanism to be in the region of the mesial thalamus, hypothalamus, and subthalamus. Kelly and co-workers, in turn, postulated that the tegmentum near the periaqueductal grey contains the integrating mechanism for emotional expression. Thus, supranuclear pathways, including those from the limbic system that Papez hypothesised to mediate emotional expressions such as laughter, probably come into synaptic relation in the reticular core of the brain stem. So while purely emotional responses such as laughter are mediated by subcortical structures, especially the hypothalamus, and are stereotyped, the cerebral cortex can modulate or suppress them."

Some drugs are well known for their laughter-facilitating properties (e. g. ethanol and cannabis), while the others, like salvinorin A (the active ingredient of Salvia divinorum), can even induce bursts of uncontrollable laughter.

A research article was published December 1, 2000, on the psycho-evolution of laughter (Panksepp 2000).

Health

A link between laughter and healthy function of blood vessels was first reported in 2005 by researchers at the University of Maryland Medical Center with the fact that laughter causes the dilatation of the inner lining of blood vessels, the endothelium, and increases blood flow. Drs. Michael Miller (University of Maryland) and William Fry (Stanford) theorize that beta-endorphin-like compounds released by the hypothalamus activate receptors on the endothelial surface to release nitric oxide, thereby resulting in dilation of vessels. Other cardioprotective properties of nitric oxide include reduction of inflammation and decreased platelet aggregation.

Laughter has various proven beneficial biochemical effects. It has been shown to lead to reductions in stress hormones such as cortisol and epinephrine. When laughing, the brain releases endorphins that can relieve some physical pain. Laughter also boosts the number of antibody-producing cells and enhances the effectiveness of T-cells, leading to a stronger immune system. A 2000 study found that people with heart disease were 40 percent less likely to laugh and be able to recognize humor in a variety of situations, compared to people of the same age without heart disease.

Anecdotally, journalist and author Norman Cousins developed in 1964 a treatment program for his ankylosing spondylitis and collagen disease consisting of large doses of Vitamin C alongside laughter induced by comic films, including those of the Marx Brothers. "I made the joyous discovery that ten minutes of genuine belly laughter had an anesthetic effect and would give me at least two hours of pain-free sleep," he reported. "When the pain-killing effect of the laughter wore off, we would switch on the motion picture projector again and not infrequently, it would lead to another pain-free interval."

Communication

A number of studies using methods of conversation analysis and discourse analysis have documented the systematic workings of laughter in a variety of interactions, from casual conversations to interviews, meetings, and therapy sessions. Working with recorded interactions, researchers have created detailed transcripts that indicate not only the presence of laughter but also features of its production and placement.

These studies challenge several widely held assumptions about the nature of laughter. Contrary to notions that it is spontaneous and involuntary, research documents that laughter is sequentially organized and precisely placed relative to surrounding talk. Far more than merely a response to humor, laughter often works to manage delicate and serious moments. More than simply an external behavior "caused" by an inner state, laughter is highly communicative and helps accomplish actions and regulate relationships.

Causes

Laughter is a common response to tickling

 

See also: Theories of humor

Common causes for laughter are sensations of joy and humor; however, other situations may cause laughter as well.

A general theory that explains laughter is called the relief theory. Sigmund Freud summarized it in his theory that laughter releases tension and "psychic energy". This theory is one of the justifications of the beliefs that laughter is beneficial for one's health. This theory explains why laughter can be used as a coping mechanism when one is upset, angry or sad.

Philosopher John Morreall theorizes that human laughter may have its biological origins as a kind of shared expression of relief at the passing of danger. Friedrich Nietzsche, by contrast, suggested laughter to be a reaction to the sense of existential loneliness and mortality that only humans feel.

For example: a joke creates an inconsistency and the audience automatically tries to understand what the inconsistency means; if they are successful in solving this 'cognitive riddle' and they realize that the surprise was not dangerous, they laugh with relief. Otherwise, if the inconsistency is not resolved, there is no laugh, as Mack Sennett pointed out: "when the audience is confused, it doesn't laugh." This is one of the basic laws of a comedian, referred to as "exactness". It is important to note that sometimes the inconsistency may be resolved and there may still be no laugh. Because laughter is a social mechanism, an audience may not feel as if they are in danger, and the laugh may not occur. In addition, the extent of the inconsistency (and aspects of its timing and rhythm) has to do with the amount of danger the audience feels, and how hard or long they laugh.

Laughter can also be brought on by tickling. Although most people find it unpleasant, being tickled often causes heavy laughter, thought to be an (often uncontrollable) reflex of the body.

Two laughing men by Hans von Aachen, circa 1574

Structure and anatomy

A normal laugh has the structure of "ha-ha-ha" or "ho-ho-ho". It is unnatural, and one is physically unable, to have a laugh structure of "ha-ho-ha-ho". The usual variations of a laugh most often occur in the first or final note in a sequence- therefore, "ho-ha-ha" or "ha-ha-ho" laughs are possible. Normal note durations with unusually long or short "inter-note intervals" do not happen due to the result of the limitations of our vocal cords. This basic structure allows one to recognize a laugh despite individual variants.

It has also been determined that eyes moisten during laughter as a reflex from the tear glands.

Negative aspects

Laughter is not always a pleasant experience and is associated with several negative phenomena. Excessive laughter can lead to cataplexy, and unpleasant laughter spells, excessive elation, and fits of laughter can all be considered negative aspects of laughter. Unpleasant laughter spells, or "sham mirth," usually occur in people who have a neurological condition, including patients with pseudobulbar palsy, multiple sclerosis and Parkinson's disease. These patients appear to be laughing out of amusement but report that they are feeling undesirable sensations "at the time of the punch line".

Excessive elation is a common symptom associated with bipolar disorder psychoses and mania/hypomania. Those with schizophrenic psychoses seem to experience the opposite—they do not understand humor or get any joy out of it. A fit describes an abnormal time when one cannot control the laughter or one's body, sometimes leading to seizures or a brief period of unconsciousness. Some believe that fits of laughter represent a form of epilepsy.

Therapy

Laughter has been used as a therapeutic tool for many years because it is a natural form of medicine. Laughter is available to everyone and it provides benefits to a person's physical, emotional, and social well being. Some of the benefits of using laughter therapy are that it can relieve stress and relax the whole body. It can also boost the immune system and release endorphins to relieve pain. Additionally, laughter can help prevent heart disease by increasing blood flow and improving the function of blood vessels. Some of the emotional benefits include diminishing anxiety or fear, improving overall mood, and adding joy to one's life. Laughter is also known to reduce allergic reactions in a preliminary study related to dust mite allergy sufferers.

Laughter therapy also has some social benefits, such as strengthening relationships, improving teamwork and reducing conflicts, and making oneself more attractive to others. Therefore, whether a person is trying to cope with a terminal illness or just trying to manage their stress or anxiety levels, laughter therapy can be a significant enhancement to their life.

Ramon Mora-Ripoll in his study on The Therapeutic Value Of Laughter In Medicine, stated that laughter therapy is an inexpensive and simple tool that can be used in patient care. It is a tool that is only beneficial when experienced and shared. Care givers need to recognize the importance of laughter and possess the right attitude to pass it on. He went on to say that since this type of therapy is not widely practiced, health care providers will have to learn how to effectively use it. In another survey, researchers looked at how Occupational Therapists and other care givers viewed and used humor with patients as a means of therapy. Many agreed that while they believed it was beneficial to the patients, the proper training was lacking in order to effectively use It. Even though laughter and humor has been used therapeutically in medical conditions, according to Mora-Ripoll, there was not enough data to clearly establish that laughter could be used as an overall means of healing. It did suggest that additional research was still needed since "well-designed randomized controlled trials have not been conducted to date validating the therapeutic efficacy of laughter."

In 2017, an institution in Japan conducted an open-label randomized controlled trial to evaluate the effects of laughter therapy on quality of life in patients with cancer. The study used laughter yoga, comedy, clown and jokes. The result showed that laughter therapy was helpful in improving quality of life and cancer symptoms in some areas for cancer survivors. Improvements were seen in the area of depression, anxiety and stress levels. There were limited harmful side effects. Laughter therapy should be used in conjunction with other cancer treatment.

Research and philosophy

Main article: Gelotology

 

Late 19th-century or early 20th-century depiction of different stages of laughter on advertising cards

Laughter in literature, although considered understudied by some, is a subject that has received attention in the written word for millennia. The use of humor and laughter in literary works has been studied and analyzed by many thinkers and writers, from the Ancient Greek philosophers onward. Henri Bergson's Laughter: An Essay on the Meaning of the Comic (Le rire, 1901) is a notable 20th-century contribution.

Ancient

Herodotus

For Herodotus, laughers can be distinguished into three types:

• Those who are innocent of wrongdoing, but ignorant of their own vulnerability
• Those who are mad
• Those who are overconfident

According to Donald Lateiner, Herodotus reports about laughter for valid literary and historiological reasons. "Herodotus believes either that both nature (better, the gods' direction of it) and human nature coincide sufficiently, or that the latter is but an aspect or analogue of the former, so that to the recipient the outcome is suggested." When reporting laughter, Herodotus does so in the conviction that it tells the reader something about the future and/or the character of the person laughing. It is also in this sense that it is not coincidental that in about 80% of the times when Herodotus speaks about laughter it is followed by a retribution. "Men whose laughter deserves report are marked, because laughter connotes scornful disdain, disdain feeling of superiority, and this feeling and the actions which stem from it attract the wrath of the gods."

Modern

See also: Theories of humor

 

Comedian Harold Lloyd laughing.

There is a wide range of experiences with laughter. A 1999 study by two humor researchers asked 80 people to keep a daily laughter record, and found they laughed an average of 18 times per day. However, their study also found a wide range, with some people laughing as many as 89 times per day, and others laughing as few as 0 times per day.

Hobbes

Thomas Hobbes wrote, "The passion of laughter is nothing else but sudden glory arising from sudden conception of some eminency in ourselves, by comparison with the infirmity of others, or with our own formerly."

Schopenhauer

Philosopher Arthur Schopenhauer devotes the 13th chapter of the first part of his major work, The World as Will and Representation, to laughter.

Nietzsche

Friedrich Nietzsche distinguishes two different purposes for the use of laughter. In a positive sense, "man uses the comical as a therapy against the restraining jacket of logic, morality and reason. He needs from time to time a harmless demotion from reason and hardship and in this sense laughter has a positive character for Nietzsche." Laughter can, however, also have a negative connotation when it is used for the expression of social conflict. This is expressed, for instance, in The Gay Science : "Laughter -- Laughter means to be schadenfroh, but with clear conscience."

"Possibly Nietzsche's works would have had a totally different effect, if the playful, ironical and joking in his writings would have been factored in better"

Bergson

In Laughter: An Essay on the Meaning of the Comic, French philosopher Henri Bergson, renowned for his philosophical studies on materiality, memory, life and consciousness, tries to determine the laws of the comic and to understand the fundamental causes of comic situations. His method consists in determining the causes of the comic instead of analyzing its effects. He also deals with laughter in relation to human life, collective imagination and art, to have a better knowledge of society. One of the theories of the essay is that laughter, as a collective activity, has a social and moral role, in forcing people to eliminate their vices. It is a factor of uniformity of behaviours, as it condemns ludicrous and eccentric behaviours.

Ludovici

Anthony Ludovici developed the thoughts of Hobbes even further in The Secret of Laughter. His conviction is that there's something sinister in laughter, and that the modern omnipresence of humour and the idolatry of it are signs of societal weakness, as instinctive resort to humour became a sort of escapism from responsibility and action. Ludovici considered laughter to be an evolutionary trait and he offered many examples of different triggers for laughter with their own distinct explanations.

Bellieni

Carlo Bellieni examined laughterin an essay published in New Ideas in Psychology. He wrote we can strip back laughter to a three-step process. First, it needs a situation that seems odd and induces a sense of incongruity (bewilderment or panic). Second, the worry or stress the incongruous situation has provoked must be worked out and overcome (resolution). Third, the actual release of laughter acts as an all-clear siren to alert bystanders (relief) that they are safe.

Flirting

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Flirting 

 

A poster by Henri Gerbault depicting flirting between a man and a woman

Flirting or coquetry is a social and sexual behavior involving spoken or written communication, as well as body language, by one person to another, either to suggest interest in a deeper relationship with the other person, or if done playfully, for amusement.

Flirting usually involves speaking and behaving in a way that suggests a mildly greater intimacy than the actual relationship between the parties would justify, though within the rules of social etiquette, which generally disapproves of a direct expression of sexual interest in the given setting. This may be accomplished by communicating a sense of playfulness or irony. Double entendres (where one meaning is more formally appropriate, and another more suggestive) may be used. Body language can include flicking the hair, eye contact, brief touching, open stances, proximity, and other gestures. Flirting may be done in an under-exaggerated, shy or frivolous style. Vocal communication of interest can include, for example,

• alterations in vocal tone (such as pace, volume, and intonation),
• challenges (including teasing, questions, qualifying, and feigned disinterest), which may serve to increase tension, and to test intention and congruity
• adoration which includes offers, approval and tact, knowledge and demonstration of poise, self-assurance, smart and stylish, a commanding attitude.

Flirting behavior varies across cultures due to different modes of social etiquette, such as how closely people should stand (proxemics), how long to hold eye contact, how much touching is appropriate and so forth. Nonetheless, some behaviors may be more universal. For example, ethologist Irenäus Eibl-Eibesfeldt found that in places as different as Africa and North America, women exhibit similar flirting behavior, such as a prolonged stare followed by a nonchalant break of gaze along with a little smile.

Laurel (played by Marilyn Monroe) flirting with Dr. Fulton (played by Cary Grant) in the film Monkey Business

Etymology

The origin of the word flirt is obscure. The Oxford English Dictionary (first edition) associates it with such onomatopoeic words as flit and flick, emphasizing a lack of seriousness; on the other hand, it has been attributed to the old French conter fleurette, which means "to (try to) seduce" by the dropping of flower petals, that is, "to speak sweet nothings". While old-fashioned, this expression is still used in French, often mockingly, but the English gallicism to flirt has made its way and has now become an anglicism.

The word fleurette was used in the 16th century in some sonnets, and some other texts. The French word fleurette (small flower), and the language of old south France word flouretas (from the Latin flora (for flower)), are related to some little says where flowers are both at the same time a pretext and the comparison terms. In southern France, some usage were yet used in 1484, In French, some other words more or less related are derived from the word fleur: for instance effleurer (English: lightly touch) from 13th century esflourée; déflorer (English: deflower) from 13th century desflorer or (fleuret (English Foil) 18th century.

The association of flowers, spring, youth, and women is not modern and were yet considered in ancient culture, such as the Chloris in ancient Greece, or Flora (deity) in the ancient Roman Empire, including Floralia festival, and in other older poems, such as the Song of Songs.

History

During World War II, anthropologist Margaret Mead was working in Britain for the British Ministry of Information and later for the U.S. Office of War Information, delivering speeches and writing articles to help the American soldiers better understand the British civilians, and vice versa. She observed in the flirtations between the American soldiers and British women a pattern of misunderstandings regarding who is supposed to take which initiative. She wrote of the Americans, "The boy learns to make advances and rely upon the girl to repulse them whenever they are inappropriate to the state of feeling between the pair", as contrasted to the British, where "the girl is reared to depend upon a slight barrier of chilliness... which the boys learn to respect, and for the rest to rely upon the men to approach or advance, as warranted by the situation." This resulted, for example, in British women interpreting an American soldier's gregariousness as something more intimate or serious than he had intended.

Communications theorist Paul Watzlawick used this situation, where "both American soldiers and British girls accused one another of being sexually brash", as an example of differences in "punctuation" in interpersonal communications. He wrote that courtship in both cultures used approximately 30 steps from "first eye contact to the ultimate consummation", but that the sequence of the steps was different. For example, kissing might be an early step in the American pattern but a relatively intimate act in the English pattern.

Japanese courtesans had another form of flirting, emphasizing non-verbal relationships by hiding the lips and showing the eyes, as depicted in much Shunga art, the most popular print media at the time, until the late 19th century.

European hand fans

Further information: European hand fans in the 18th century

The fan was extensively used as a means of communication and therefore a way of flirting from the 16th century onwards in some European societies, especially England and Spain. A whole sign language was developed with the use of the fan, and even etiquette books and magazines were published. Charles Francis Badini created the Original Fanology or Ladies' Conversation Fan which was published by William Cock in London in 1797. The use of the fan was not limited to women, as men also carried fans and learned how to convey messages with them. For instance, placing the fan near the heart meant "I love you", while opening a fan wide meant "Wait for me".

In Spain, where the use of fans (called "abanicos") is still very popular today, ladies used them to communicate with suitors or prospective suitors without attracting the notice of their families or chaperons. This use was highly popular during the 19th and early 20th centuries.

Purpose

A woman flirts with a soldier by tickling him with a feather.

People flirt for a variety of reasons. According to social anthropologist Kate Fox, there are two main types of flirting: flirting just for fun and flirting with further intent.

In a 2014 review, Henningsen made a further distinction and identified six main motivations for flirting: sex, relational development, exploration, fun, self-esteem and instrumental. Henningsen found that often, many flirting interactions involve more than one of these motives. There also appears to be gender differences in flirting motivations.

Courtship

Many people flirt as a courtship initiation method, with the aim of engaging in a sexual relationship with another person. In this sense, flirting plays a role in the mate-selection process. The person flirting will send out signals of sexual availability to another, and expects to see the interest returned in order to continue flirting. Flirting can involve non-verbal signs, such as an exchange of glances, hand-touching, and hair-touching; or verbal signs, such as chatting, giving flattering comments, and exchanging telephone numbers in order to initiate further contact.

Many studies have confirmed that sex is a driving motivation for flirting behaviours. Additionally, Messman and colleagues' study provided support for this hypothesis; it demonstrated that, the more one was physically attracted to a person, the higher the chances one would flirt with them.

Flirting with the goal of signalling interest appears as a puzzling phenomenon when considering that flirting is often performed very subtly. In fact, evidence shows that people are often mistaken in how they interpret flirting behaviours. Logically, if the main purpose of flirting is to signal interest to the other person, then the signalling would be done clearly and explicitly. A possible explanation for the ambiguous nature of human flirting lies in the costs associated with courtship signals. Indeed, according to Gersick and colleagues, signalling interest can be costly as it can lead to the disturbance of the nature of a relationship. For instance, signalling sexual interest to a friend bears the risk of introducing uncertainty into the friendship, especially if the romantic advance is rejected by the recipient. For this reason, individuals prefer engaging in a flirting interaction that is more subtle to limit the risks associated with the expression of sexual interest.

More generally, human relationships are governed by social norms and whenever these are broken, one can suffer significant costs that can range from social, economic and even legal nature. As an illustration, a manager flirting with his subordinate can lead to strong costs such as being accused of sexual harassment, which can potentially lead to job loss.

Additionally, third parties can impose costs on someone expressing sexual interest. Expressing sexual interest to somebody else's romantic partner is a highly punishable act. This often leads to jealousy from the person's partner which can trigger anger and (possible) physical punishment, especially in men. Third parties can also impose costs through the act of eavesdropping. These can lead to damage to one's reputation leading to possible social, economic and legal costs.

A last point to consider is that the costs associated with interest signalling are magnified in the case of humans, when compared to the animal world. Indeed, the existence of language means that information can circulate much faster. For instance, in the case of eavesdropping, the information overhead by the eavesdropper can be spread to very large social networks, thereby magnifying the social costs.

Other motivations

Another reason people engage in flirting is to consolidate or maintain a romantic relationship with their partner. They will engage in flirting behaviours to promote the flourishing of their relationship with their partner. People will also flirt with the goal of 'exploring'. In this sense, the aim is not necessarily to express sexual or romantic interest but simply to assess whether the other might be interested in them before making any decision about what they would want from that individual.

Henningsen and Fox also demonstrated that flirting can sometimes be employed just for fun. For instance, studies have shown that flirting in the workplace was used mostly for fun purposes.

Another motive that drives flirting is developing one's own self esteem. People often feel highly valued when someone flirts with them. Therefore, often people flirt to encourage reciprocation and thereby increase their self esteem.

As a last point, people might flirt for instrumental purposes. For instance, they will flirt to get something out of the other person such as a drink in a nightclub or a promotion at work.

Gender differences in motivations

Certain types of flirting seem to be more common amongst males compared to females and vice versa.

To start with, Henningsen and colleagues' study demonstrated that flirting with sexual intent was found to be more prominent amongst men. On the other hand, flirting for relationship development purposes was more often employed by women.

These findings are not surprising when the parental investment theory is taken into account. First, it states that females are more choosy and men more competitive, therefore predicting that flirting as courtship initiation will be more commonly used amongst men. The theory also predicts that females invest more in their offspring, which makes them more prone to invest in their relationship as this can provide resources that can contribute to their offspring's survival. On the other hand, men have no guarantee that their mates' offspring is theirs, so have fewer incentives to seek long-term relationships; thereby explaining why men care less about flirting for relationship development.

Additionally, Henningsen found that flirting for fun was more common in females than males. A possible explanation for this could lie in the fact that women engage in what he calls "practice flirting". As women are more selective and want to attract the best partner to take care of their offspring, they might flirt for fun to practice and evaluate what flirting behaviours work the best.

Examples

A study in body language: Haynes King's Jealousy and Flirtation

Flirting may consist of stylized gestures, language, body language, postures, and physiologic signs which act as cues to another person. Among these, at least in Western society, are:

• Blowing a kiss
• Casual touching; such as gently stroking, touching each other's arms, chest and neck during flirting/heavy, intimate make-out sessions in preparation for sexual activity
• Conversation (e.g. banter, small talk, pickup lines)
• Coyness, marked by cute, coquettish shyness or modesty, coquet or playful aggrandizement of a partner's importance
• Eye contact, batting eyelashes, or staring
• Eyebrow raising
• Flattery (e.g. regarding beauty, sexual attractiveness)
• Footsie, a form of flirtation in which one uses their feet to play with another's
• Hugging
• Imitating or mirroring another's behavior (e.g. taking a drink when the other person takes a drink, changing posture as the other does, foreshadowing or mimicking someone's reactions to successful attraction etc.)
• Laughing, giggling, chuckling encouragingly at any slight hint of intimacy in the other's behavior
• Maintaining close proximity, such as during casual talking
• Nicknames and other terms of endearment to describe a partner's personality, beauty or sexiness
• Chatting online, texting, and using other one-on-one and direct messaging services, while hinting affection
• Protean signals or indicators of interest, such as touching one's hair, side-ways glance, and pointing one's chest towards partner's chest
• Partner dancing
• Writing love letters and notes, poems, or presenting small gifts
• Singing specially selected love songs as a declaration of love and devotion in presence of one's partner
• Smiling or grinning at partner and/or holding them close
• Staging of "chance" encounters and romantic rendezvous
• Sexting
• Teasing
• Tickling
• Winking

The effectiveness of many of these interactions has been subjected to detailed analysis by behavioral psychologists, and advice on their use is available from dating coaches.

Cultural variations

Flirting varies a great deal from culture to culture. For example, for many Western cultures one very common flirting strategy includes eye contact. However, eye contact can have a very different meaning in some Asian countries, where women might get in trouble if they return a glance to men who stare at them. Furthermore, Chinese and Japanese women are sometimes not expected to initiate eye contact as it could be considered rude and disrespectful.

The Flirtation by Eugene de Blaas. A study of body language: a man flirting

The distance between two people is also important when flirting. People from the "contact cultures", such as those in the Mediterranean or Latin America, may feel comfortable with closer proximity, whereas a British or Northern European person may typically need more space. Although touching, especially of the hand or arm, can constitute flirting, touching is also often done without intentions of flirting, particularly in the contact cultures where it forms a natural part of communication.

In Japan, flirting in the street or public places is known as nanpa.

Philosophy of love

From Wikipedia, the free encyclopedia

 https://en.wikipedia.org/wiki/Philosophy_of_love

Philosophy of love is the field of social philosophy and ethics that attempts to explain the nature of love.

Current theories

There are many different theories that attempt to explain what love is, and what function it serves. It would be very difficult to explain love to a hypothetical person who had not himself or herself experienced love or being loved. In fact, to such a person love would appear to be quite strange if not outright irrational behavior.  Among the prevailing types of theories that attempt to account for the existence of love there are: psychological theories, the vast majority of which consider love to be very healthy behavior. Psychologists like Eric Erikson for example who believed that finding intimacy was a necessary part of human development. There are evolutionary theories that hold that love is part of the process of natural selection; there are spiritual theories that may, for instance consider love to be a gift from God; there are also theories that consider love to be an unexplainable mystery, very much like a mystical experience.

Western traditions

Classical roots

Setting aside Empedocles's view of Eros as the force binding the world together, the roots of the classical philosophy of love go back to Plato's Symposium. Plato's Symposium digs deeper into the idea of love and bringing different interpretations and points of view in order to define love. From its riches, we may perhaps single out three main threads that would continue to reverberate through the centuries that followed.

1. The idea of two loves, one heavenly, one earthly. As Uncle Toby was informed, over two millennia later, "of these loves, according to Ficinus's comment on Valesius, the one is rational - the other is natural - the first...excites to the desire of philosophy and truth - the second, excites to desire, simply".
2. Aristophanes's conception of mankind as the product of the splitting in two of an original whole: Freud would later draw on this myth - "everything about these primaeval men was double: they had four hands and four feet, two faces" - to support his theory of the repetition compulsion.
3. Plato's sublimation theory of love - "mounting upwards...from one to two, and from two to all fair forms, and from fair forms to fair actions, and from fair actions to fair notions, until from fair notions he arrives at the notion of absolute beauty".

Aristotle by contrast placed more emphasis on philia (friendship, affection) than on eros (love); and the relationship of friendship and love would continue to be played out into and through the Renaissance, with Cicero for the Latins pointing out that "it is love (amor) from which the word 'friendship' (amicitia) is derived" Meanwhile, Lucretius, building on the work of Epicurus, had both praised the role of Venus as "the guiding power of the universe", and criticised those who become "love-sick...life's best years squandered in sloth and debauchery".

Eros in greek, also known as Cupid, was the mischievous god of love. He was a companion of the goddess Aphrodite. Eros was known for sparking the flame of love in gods and men. He is known for being portrayed as being armed with a bow and arrows or a flaming torch. He is also known for being disobedient but a loyal child of Aphrodite.

Philia love is the type of friendship love. In Greek, this translated to brotherly love. Aristotle was able to describe three main types of friendships. These were Useful, Pleasurable, and Virtue. Useful was when a friendship has a benefit to it which is derived by desire. Pleasurable is based on pleasure that one receives. Lastly Virtue is when it is based on true friendship and not receiving anything from it.

Agape in Greek simply means love. The presence of agape love is when there is goodwill, benevolence, and willful delight in the object of love This type of love does not relate to that of romantic nor sexual. Nor does it refer to Philia type of love where it is a close friendship or brotherly love. What sets this love apart is how it is able to involve that of faithfulness, commitment, and an act of the will.

Petrarchism

Among his love-sick targets, Catullus, along with others like Héloïse, would find himself summoned in the 12C to a Love's Assize. From the ranks of such figures, and perhaps also under Islamic influences, would emerge the concept of courtly love; and from that Petrarchism would form the rhetorical/philosophical foundations of romantic love for the early modern world.

French skepticism

Alongside the passion for merging that marked Romantic love, a more sceptical French tradition can be traced from Stendhal onwards. Stendhal's theory of crystallization implied an imaginative readiness for love, which only needed a single trigger for the object to be imbued with every fantasised perfection. Proust went further, singling out absence, inaccessibility or jealousy as the necessary precipitants of love. Lacan would almost parody the tradition with his saying that "love is giving something you haven't got to someone who doesn't exist". A post-Lacanian like Luce Irigaray would then struggle to find room for love in a world that will "reduce the other to the same...emphasizing eroticism to the detriment of love, under the cover of sexual liberation".

Western philosophers of love

• Hesiod
• Empedocles
• Plato (Symposium)
• St Augustine
• Thomas Aquinas
• Leon Hebreo
• Baruch Spinoza
• Nicolas Malebranche
• Jean-Pierre Rousselot
• Antonio Caso Andrade
• Sigmund Freud
• Søren Kierkegaard - Works of Love
• Carl Jung
• Anders Nygren
• Martin D'Arcy
• Irving Singer - Philosophy of Love: A Partial Summing-Up
• Arthur Schopenhauer - "Metaphysics of Love"
• Thomas Jay Oord
• Friedrich Nietzsche
• Max Stirner "Egoistic Love"
• Max Scheler "The Nature of Sympathy"
• Erich Fromm, author of The Art of Loving
• C. S. Lewis, "The Four Loves"
• Michel Onfray, author of Théorie du corps amoureux : pour une érotique solaire (2000)
• Karl Popper
• Jean-Luc Marion, "The Erotic Phenomenon"
• Luce Irigaray, "The Way of Love"
• Bell Hooks - "All About Love: New Visions"
• Roger Scruton - Notes from Underground
• Carrie Ichikawa Jenkins

Eastern traditions

• Given what Max Weber called the intimate relationship between religion and sexuality, the role of the lingam and yoni in India, or of yin and yang in China, as a structuring form of cosmic polarity based on the male and female principles, is perhaps more comprehensible. By way of maithuna or sacred intercourse, Tantra developed a whole tradition of sacred sexuality, which led in its merger with Buddhism to a view of sexual love as a path to enlightenment: as Saraha put it, "That blissful delight that consists between lotus and vajra...removes all defilements".
• More soberly, the Hindu tradition of friendship as the basis for love in marriage can be traced back to the early times of the Vedas.
• Confucius is sometimes seen as articulating a philosophy (as opposed to religion) of love.