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Saturday, June 29, 2019

Democratic education

From Wikipedia, the free encyclopedia

A discussion class at Shimer College, a democratic college in Chicago
 
Democratic education is an educational ideal in which democracy is both a goal and a method of instruction. It brings democratic values to education and can include self-determination within a community of equals, as well as such values as justice, respect and trust. Democratic education is often specifically emancipatory, with the students' voices being equal to the teacher's.

History

Locke's Thoughts, 1693
 
The history of democratic education spans from at least the 1600s. While it is associated with a number of individuals, there has been no central figure, establishment, or nation that advocated democratic education.

Enlightenment era

In 1693, John Locke published Some Thoughts Concerning Education. In describing the teaching of children, he declares,
None of the things they are to learn, should ever be made a burthen to them, or impos'd on them as a task. Whatever is so propos'd, presently becomes irksome; the mind takes an aversion to it, though before it were a thing of delight or indifferency. Let a child but be order'd to whip his top at a certain time every day, whether he has or has not a mind to it; let this be but requir'd of him as a duty, wherein he must spend so many hours morning and afternoon, and see whether he will not soon be weary of any play at this rate.
Jean-Jacques Rousseau’s book of advice on education, Émile, was first published in 1762. Émile, the imaginary pupil he uses for illustration, was only to learn what he could appreciate as useful. He was to enjoy his lessons, and learn to rely on his own judgement and experience. “The tutor must not lay down precepts, he must let them be discovered,” wrote Rousseau, and urged him not make Émile learn science, but let him discover it. He also said that we should not substitute books for personal experience because this does not teach us to reason; it teaches us to use other people's reasoning; it teaches us to believe a great deal but never to know anything.

19th century

While Locke and Rousseau were concerned only with the education of the children of the wealthy, in the 19th century Leo Tolstoy set up a school for peasant children. This was on his own estate at Yasnaya Polyana, Russia, in the late 19th century. He tells us that the school evolved freely from principles introduced by teachers and pupils; that in spite of the preponderating influence of the teacher, the pupil had always had the right not to come to school, or, having come, not to listen to the teacher, and that the teacher had the right not to admit a pupil, and was able to use all the influence he could muster to win over the community, where the children were always in the majority.

20th century

Dom Sierot

In 1912, Janusz Korczak founded Dom Sierot, the Jewish orphanage in Warsaw, which was run on democratic lines until 1940, when he accompanied all his charges to the gas-chambers of the Treblinka extermination camp.

Influential democratic schools

Main building of the Summerhill School
 
The oldest democratic school that still exists is Summerhill, in Suffolk, England, founded in 1921. It features voluntary class attendance and a School Meeting with broad powers. 

Sudbury Valley School, founded in Framingham, Massachusetts in 1968, has full democratic governance: The School Meeting manages all aspects of the school, including staff hiring and facilities. A "Sudbury school" is now a general class of school modeled after this original. 

The term Democratic Education originates from The Democratic School of Hadera, the first school in the world called a democratic school. It was founded in Israel in 1987 by Yaacov Hecht. It is a public school. The term has been embraced by alternative/open schools all over the world, predominantly following the foundation of IDEC – the International Democratic Education Conference, which was first convened at the democratic school in Hadera.

Free schools movement

In the 1960s, hundreds of "free schools" opened, many based on Summerhill. However A.S. Neill, the founder of Summerhill, distanced himself from American Summerhill schools for not successfully implementing the philosophy of "Freedom, not license." Free school movement (including many schools based on Summerhill) became a broad movement in the 1960s and 1970s, but was largely renounced by the 1980s. Progressive education and Dewey's ideals did influence them, but only indirectly for the most part.

Networks

Networks supporting democratic education include:
  • The Alternative Education Resource Organization launched in 1989 to create a "student-driven, learner-centered approaches to education."
  • The annual International Democratic Education Conference, first held in 1993.
  • The Australasian Democratic Education Community, which held its first conference in 2002.
  • The European Democratic Education Community was founded in 2008, at the first European Democratic Education Conference.
  • The Réseau des écoles démocratiques au Québec, or RÉDAQ, was founded in 2012 in order to sponsor the creation of democratic schools in the province of Québec, Canada.
  • The Alliance for Self-Directed Education launched in 2016 to make Self-Directed Education a normal and accessible option for all families.
  • Democracy Matters, launched in 2009, is a UK alliance of organisations promoting education for citizenship, participation and practical politics
IDEC 2005 named two core beliefs: self-determination and democratic governance. EUDEC has both of these beliefs, and mutual respect is also in their belief statement. IDEN supports schools that self-identify as democratic.

Variety

Democratic education, same as a Democracy or a democratic government, comes in many different forms. These are some of the areas in which democratic schools differ.

Curriculum

Democratic schools are characterized by involving students in the decision-making process that affects what and how they learn. Democratic schools have no mandatory curriculum, considering forced learning to be undemocratic. Some democratic schools officially offer voluntary courses, and many help interested students to prepare for national examinations so they gain qualifications for further study or future employment. Some democratic schools have no official offering of courses, although courses can be offered or requested by school members.

Administrative structure

Democratic schools often have meetings open to all students and staff, where everyone present has a voice and sometimes an equal vote. Some include parents. These school meetings can cover anything from small matters to the appointment or dismissal of staff and the creation or annulment of rules, or to general expenditure and the structure of the school day. At some schools all students are expected to attend these meetings, at others they are voluntary. The main school meeting may also set up sub-committees to deal with particular issues, such as conflict resolution.

Conflict resolution

Within the purview of democratic values, there is wide scope for how conflicts are resolved. There may be a formal system, with due process and the rule of law. There may be rules but no punishments. Other possibilities include, but are not limited to, a consensus process, mediation, and informal dialogue.

Other

Finance: Some democratic learning environments are parent-funded, some charity-funded. Schools may have a sliding scale based on family income. Publicly funded democratic schools exist in Canada and Israel.

Size: Democratic schools vary in size from a few students to a few hundred. Even an individual unschooler can be described as learning democratically, if they are treated with democratic values. 

Age range: Age mixing is a deliberate policy in some democratic schools. It may include very young children, even babies. Some democratic schools only enroll older students.

Location: Democratic education is not limited to any particular setting. Settings for democratic learning communities include in an office building, on city streets, and in a rural area.

Theory

While types of democratic education are as numerous as types of democracy, a general definition of democratic education is "an education that democratizes learning itself." The goals of democratic education vary according to the participants, the location, and access to resources.

There is no unified body of literature, spanning multiple disciplines, on democratic education. However, there are theories of democratic education from the following perspectives:

Cognitive theory

During the practice theory movement, there was renewed interest in child development. Jean Piaget's theory of universal steps in comprehension and general patterns in the acquisition of knowledge was challenged by experiences at democratic schools. "No two kids ever take the same path. Few are remotely similar. Each child is so unique, so exceptional."

Jean Lave was one of the first and most prominent social anthropologists to discuss cognition within the context of cultural settings presenting a firm argument against the functionalist psychology that many educationalists refer to implicitly. For Lave, learning is a process undergone by an actor within a specific context. The skills or knowledge learned in one process are not generalizable nor reliably transferred to other areas of human action. Her primary focus was on mathematics in context and mathematics education. 

The broader implications reached by Lave and others who specialize in situated learning are that beyond the argument that certain knowledge is necessary to be a member of society (a Durkheimian argument), knowledge learned in the context of a school is not reliably transferable to other contexts of practice. 

John Locke argues that children are capable of reasoning at a young age: “It will perhaps be wonder’d, that I mention reasoning with children; and yet I cannot but think that the true way of dealing with them. They understand it as early as they do language; and, if I misobserve not, they love to be treated as rational creatures, sooner than is imagin’d,” Rousseau disagreed: “Use force with children and reasoning with men."

Humans are innately curious, and democratic education supports the belief that the drive to learn is sufficiently strong to motivate children to become effective adults.

Criticism based on cognitive theory

The human brain is not fully developed until adulthood. A disadvantage of teenagers being responsible for their own education is that "young brains have both fast-growing synapses and sections that remain unconnected. This leaves teens easily influenced by their environment and more prone to impulsive behavior".

Ethics

Democracy can be valued on ethical grounds.

Cultural theory

Democratic education is consistent with the cultural theory that "learning in school must be continuous with life outside of school" and that children should become active participants in the control and organization of their community.

Research on hunter-gatherer societies indicates that free play and exploration were effective transmitters of the societies' culture to children.

According to George Dennison, democratic environments are social regulators: Our desire to cultivate friendships, engender respect, and maintain what George Dennison terms ‘natural authority’ encourages us to act in socially acceptable ways (i.e. culturally informed practices of fairness, honesty, congeniality, etc.).

Criticism based on cultural theory

Children are influenced by many curricula beyond the school curriculum: TV curricula, advertisers' curricula, curricula of religious communities, Girl Scouts and Boy Scouts, encyclopedias etc. and therefore "one of the most significant tasks any school can undertake is to try to develop in youngsters an awareness of these other curricula and an ability to criticize them…it is utter nonsense to think that by turning children loose in an unplanned and unstructured environment they can be freed in any significant way. Rather, they are thereby abandoned to the blind forces of the hucksters, whose primary concern is neither the children, nor the truth, nor the decent future of ... society."

Émile Durkheim argues that the transition from primitive to modern societies occurred in part as elders made a conscious decision to transmit what were deemed the most essential elements of their culture to the following generations. He concludes that modern societies are so complex—much more complex than primitive hunter-gatherer societies—and the roles that individuals must fill in society are so varied, that formal mass-education is necessary to instill social solidarity and what he terms ‘secular morality’.

Political theory

There are a variety of political components to democratic education. One author identifies those elements as inclusivity and rights, equal participation in decision-making, and equal encouragement for success. The Institute for Democratic Education's principles of democratic education identifies several political principles,

Effect on quality of education

The type of political socialization that takes place in democratic schools is strongly related to deliberative democracy theory. Claus Offe and Ulrich Preuss, two theorists of the political culture of deliberative democracies argue that in its cultural production deliberative democracy requires “an open-ended and continuous learning process in which the roles of both ‘teacher’ and ‘curriculum’ are missing. In other words, what is to be learned is a matter that we must settle in the process of learning itself."

The political culture of a deliberative democracy and its institutions, they argue, would facilitate more “dialogical forms of making one’s voice heard” which would “be achieved within a framework of liberty, within which paternalism is replaced by autonomously adopted self-paternalism, and technocratic elitism by the competent and self-conscious judgment of citizens."

As a curricular, administrative and social operation within schools, democratic education is essentially concerned with equipping people to make "real choices about fundamental aspects of their lives" and happens within and for democracy. It can be "a process where teachers and students work collaboratively to reconstruct curriculum to include everyone." In at least one conception, democratic education teaches students "to participate in consciously reproducing their society, and conscious social reproduction." This role necessitates democratic education happening in a variety of settings and being taught by a variety of people, including "parents, teachers, public officials, and ordinary citizens." Because of this "democratic education begins not only with children who are to be taught but also with citizens who are to be their teachers."

Preparation for life in a democracy

The "strongest, political rationale" for democratic education is that it teaches "the virtues of democratic deliberation for the sake of future citizenship." This type of education is often alluded to in the deliberative democracy literature as fulfilling the necessary and fundamental social and institutional changes necessary to develop a democracy that involves intensive participation in group decision making, negotiation, and social life of consequence.

Civic education

The concept of the hidden curriculum includes the belief that anything taught in an authoritarian setting is implicitly teaching authoritarianism. Thus civic education, if taught in a compulsory setting, undermines its own lessons in democracy. A common belief in democratic schools is that democracy must be experienced to be learned. This argument conforms to the cognition-in-context research by Lave

Another common belief, which supports the practice of compulsory classes in civic education, is that passing on democratic values requires an imposed structure.

Arguments about how to transmit democracy, and how much and how early to treat children democratically, are made in various literatures concerning student voice, youth participation and other elements of youth empowerment.

Standard progressive visions of education as collaboration tend to downplay the workings of power in society. If learners are to "develop a democracy," some scholars have argued, they must be provided the tools for transforming the non-democratic aspects of a society. Democracy in this sense involves not just "participation in decision making," a vision ascribed especially to Dewey, but the ability to confront power with solidarity.

Economic theory

Core features of democratic education align with the emerging consensus on 21st century business and management priorities. Such features include increased collaboration, decentralized organization, and radical creativity.

Curriculum theory

While democratic schools don't have an official curriculum, what each student actually does might be considered their own curriculum. Dewey was an early advocate of inquiry education, in which student questions and interests shaped curriculum, a sharp contrast to the "factory model" that began to predominate education during the 20th century as standardization became a guiding principle of many educational practices. Although there was a resurgence of inquiry education in the 1980s and 1990s  the standards movement of the 21st century and the attendant school reform movement have squashed most attempts at authentic inquiry-oriented democratic education practices. The standards movement has reified standardized tests in literacy and writing, neglecting science inquiry, the arts, and critical literacy. 

Democratic schools may not consider only reading, writing and arithmetic to be the real basics for being a successful adult. A.S. Neill said "To hell with arithmetic." Nonetheless, there is a common belief that people will eventually learn "the basics" when they develop internal motivation. Furthermore, an educator implementing inquiry projects will look at the "next steps" in a student's learning and incorporate basic subject matter as needed. This is easier to accomplish in elementary school settings than in secondary school settings, as elementary teachers typically teach all subjects and have large blocks of time that allow for in-depth projects that integrate curriculum from different knowledge domains. 

Allen Koshewa conducted research that highlighted the tensions between democratic education and the role of teacher control, showing that children in a fifth grade classroom tried to usurp democratic practices by using undue influence to sway others, much as representative democracies often fail to focus on the common good or protect minority interests. He found that class meetings, service education, saturation in the arts, and an emphasis on interpersonal caring helped overcome some of these challenges. Despite the challenges of inquiry education, classrooms that allow students to make choices about curriculum propel students to not only learn about democracy but also to experience it.

Democratic education in practice

Play

A striking feature of democratic schools is the ubiquity of play. Students of all ages — but especially the younger ones — often spend most of their time either in free play, or playing games (electronic or otherwise). All attempts to limit, control or direct play must be democratically approved before being implemented. Play is seen as activity every bit as worthy as academic pursuits, often even more valuable. Play is considered essential for learning, particularly in fostering creativity.

Reading, writing and arithmetic

It was Invented by Liam Doherty. Interest in learning to read happens at a wide variety of ages. Progressive educators emphasise students' choice in reading selections, as well as topics for writing. In addition, Stephen Krashen  and other proponents of democratic education emphasise the role of libraries in promoting democratic education. Others, such as children's author Judy Blume, have spoken out against censorship as antagonistic to democratic education, while the school reform movement, which gained traction under the federal initiative 'No Child Left Behind' and later under 'Race to the Top' and the Common Core Standards movement, emphasise strict control over curriculum.

Education in a democratic society

As English aristocracy was giving way to democracy, Matthew Arnold investigated popular education in France and other countries to determine what form of education suited a democratic age. Arnold wrote that "the spirit of democracy" is part of "human nature itself", which engages in "the effort to affirm one's own essence...to develop one's own existence fully and freely."

During the industrial age, John Dewey argued that children should not all be given the same pre-determined curriculum. In Democracy and Education he develops a philosophy of education based on democracy. He argues that while children should be active participants in the creation of their education, and while children must experience democracy to learn democracy, they need adult guidance to develop into responsible adults.

Amy Gutmann argues in Democratic Education that in a democratic society, there is a role for everyone in the education of children. These roles are best agreed upon through deliberative democracy.

The journal Democracy and Education investigates "the conceptual foundations, social policies, institutional structures, and teaching/learning practices associated with democratic education." By "democratic education" they mean "educating youth...for active participation in a democratic society."

Yaacov Hecht claims that the Democratic Education, being an education that prepares for life in a democratic culture, it is the missing piece in the intricate puzzle which is the democratic state.

Training programs

Israel's Institute for Democratic Education and Kibbutzim College in Tel Aviv collaborate to offer a Bachelor of Education (B. Ed.) degree with a Specialization Certificate in Democratic Education. Student teaching placements are in both regular schools and democratic schools.

Legal issues

The United Nations and democratic education

United Nations agreements both support and place restrictions on education options, including democratic education: 

Article 26(3) of the United Nations Universal Declaration of Human Rights states that "Parents have a prior right to choose the kind of education that shall be given to their children." While this in itself may allow parents the right to choose democratic education, Articles 28 and 29 of the United Nations Convention on the Rights of the Child place requirements on educational programs: Primary education is compulsory, all aspects of each student must be developed to their full potential, and education must include the development of respect for things such as national values and the natural environment, in a spirit of friendship among all peoples.

Furthermore, while Article 12(1) of the Convention mandates that children be able to have input on all matters that affect them, their input will have limited weight, "due weight in accordance with the age and maturity of the child."

Summerhill

In 1999, Summerhill received a 'notice of complaint' over its policy of non-compulsory lessons, a procedure which would usually have led to closure; Summerhill contested the notice and went before a special educational tribunal. Summerhill was represented by a noted human rights lawyer, Geoffrey Robertson QC. The government's case soon collapsed, and a settlement was offered. This offer was discussed and agreed at a formal school meeting which had been hastily convened in the courtroom from a quorum of pupils and teachers who were present in court. The settlement guaranteed that future inspections of Summerhill would be consistent with Summerhill's educational philosophy.

Theorists

  • Joseph Agassi - Israeli philosopher and proponent of democracy
  • Michael Apple - Social scientist, democratic education scholar, University of Wisconsin–Madison
  • Matthew Arnold - Wrote about education in an age of democracy
  • Sreyashi Jhumki Basu - Researcher at New York University and author of Democratic Science Teaching
  • Pierre Bourdieu - Anthropologist, social theorist, College de France
  • George Dennison - American writer, author
  • John Dewey - Social scientist, progressive education theorist, University of Chicago
  • Émile Durkheim - Sociologist, functionalist education theorist
  • Michel Foucault - Post-modern philosopher, University of California, Berkeley
  • Peter Gray - Psychologist, democratic education scholar, Boston College
  • Daniel Greenberg - One of the founders of the Sudbury Valley School
  • Amy Gutmann - Political scientist, democratic education scholar, President of the University of Pennsylvania
  • Yaacov Hecht – founder of the school in Hadera, the first in the world to be called a democratic school, and founder of IDEC.
  • John Holt - Critic of conventional education and proponent of un-schooling, which can be also done at home
  • Ivan Illich - Philosopher, priest, author of "Deschooling Society"
  • Lawrence Kohlberg - Professor, pioneer in moral and democratic education
  • Homer Lane - Democratic education pioneer, founder of the Ford Republic (1907–12) and the Little Commonwealth (1913–17)
  • Deborah Meier - Founder of democratic schools in New York and Boston, writer
  • A.S. Neill - Democratic education pioneer, founder of the Summerhill School
  • Claus Offe - Political Scientist, theorist of deliberative democratic culture, Hertie School of Governance
  • Karl Popper - Philosopher at the London School of Economics
  • Bertrand Russell - Philosopher, author of On Education and founder of Beacon House School

Osmium

From Wikipedia, the free encyclopedia

Osmium,  76Os
Osmium crystals.jpg
Osmium
Pronunciation/ˈɒzmiəm/ (OZ-mee-əm)
Appearancesilvery, blue cast
Standard atomic weight Ar, std(Os)190.23(3)
Osmium in the periodic table
Hydrogen
Helium
Lithium Beryllium
Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium
Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium
Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium

Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ru

Os

Hs
rheniumosmiumiridium
Atomic number (Z)76
Groupgroup 8
Periodperiod 6
Blockd-block
Element category  Transition metal
Electron configuration[Xe] 4f14 5d6 6s2
Electrons per shell
2, 8, 18, 32, 14, 2
Physical properties
Phase at STPsolid
Melting point3306 K ​(3033 °C, ​5491 °F)
Boiling point5285 K ​(5012 °C, ​9054 °F)
Density (near r.t.)22.59 g/cm3
when liquid (at m.p.)20 g/cm3
Heat of fusion31 kJ/mol
Heat of vaporization378 kJ/mol
Molar heat capacity24.7 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 3160 3423 3751 4148 4638 5256
Atomic properties
Oxidation states−4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8 (a mildly acidic oxide)
ElectronegativityPauling scale: 2.2
Ionization energies
  • 1st: 840 kJ/mol
  • 2nd: 1600 kJ/mol

Atomic radiusempirical: 135 pm
Covalent radius144±4 pm
Color lines in a spectral range
Spectral lines of osmium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for osmium
Speed of sound thin rod4940 m/s (at 20 °C)
Thermal expansion5.1 µm/(m·K) (at 25 °C)
Thermal conductivity87.6 W/(m·K)
Electrical resistivity81.2 nΩ·m (at 0 °C)
Magnetic orderingparamagnetic
Magnetic susceptibility11·10−6 cm3/mol
Shear modulus222 GPa
Bulk modulus462 GPa
Poisson ratio0.25
Mohs hardness7.0
Vickers hardness300 MPa
Brinell hardness293 MPa
CAS Number7440-04-2
History
Discovery and first isolationSmithson Tennant (1803)
Main isotopes of osmium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
184Os 0.02% stable
185Os syn 93.6 d ε 185Re
186Os 1.59% 2.0×1015 y α 182W
187Os 1.96% stable
188Os 13.24% stable
189Os 16.15% stable
190Os 26.26% stable
191Os syn 15.4 d β 191Ir
192Os 40.78% stable
193Os syn 30.11 d β 193Ir
194Os syn 6 y β 194Ir

Osmium (from Greek ὀσμή osme, "smell") is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with an experimentally measured (using x-ray crystallography) density of 22.59 g/cm3. Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. The element's abundance in the Earth's crust is among the rarest.

Characteristics

Physical properties

Osmium, remelted pellet
 
Osmium has a blue-gray tint and is the densest stable element; it is approximately twice as dense as lead and slightly denser than iridium. Calculations of density from the X-ray diffraction data may produce the most reliable data for these elements, giving a value of 22.587±0.009 g/cm3 for osmium, slightly denser than the 22.562±0.009 g/cm3 of iridium; both metals are nearly 23 times as dense as water.

Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility. Correspondingly, its bulk modulus is extremely high, reported between 395 and 462 GPa, which rivals that of diamond (443 GPa). The hardness of osmium is moderately high at 4 GPa. Because of its hardness, brittleness, low vapor pressure (the lowest of the platinum-group metals), and very high melting point (the fourth highest of all elements, after only carbon, tungsten, and rhenium), solid osmium is difficult to machine, form, or work.

Chemical properties

Osmium forms compounds with oxidation states ranging from −2 to +8. The most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element aside from iridium's +9 and is encountered only in xenon, ruthenium, hassium, and iridium. The oxidation states −1 and −2 represented by the two reactive compounds Na
2
[Os
4
(CO)
13
]
and Na
2
[Os(CO)
4
]
are used in the synthesis of osmium cluster compounds.

The most common compound exhibiting the +8 oxidation state is osmium tetroxide. This toxic compound is formed when powdered osmium is exposed to air. It is a very volatile, water-soluble, pale yellow, crystalline solid with a strong smell. Osmium powder has the characteristic smell of osmium tetroxide. Osmium tetroxide forms red osmates OsO
4
(OH)2−
2
upon reaction with a base. With ammonia, it forms the nitrido-osmates OsO
3
N
. Osmium tetroxide boils at 130 °C and is a powerful oxidizing agent. By contrast, osmium dioxide (OsO2) is black, non-volatile, and much less reactive and toxic. 

Only two osmium compounds have major applications: osmium tetroxide for staining tissue in electron microscopy and for the oxidation of alkenes in organic synthesis, and the non-volatile osmates for organic oxidation reactions.

Osmium pentafluoride (OsF5) is known, but osmium trifluoride (OsF3) has not yet been synthesized. The lower oxidation states are stabilized by the larger halogens, so that the trichloride, tribromide, triiodide, and even diiodide are known. The oxidation state +1 is known only for osmium iodide (OsI), whereas several carbonyl complexes of osmium, such as triosmium dodecacarbonyl (Os
3
(CO)
12
), represent oxidation state 0.

In general, the lower oxidation states of osmium are stabilized by ligands that are good σ-donors (such as amines) and π-acceptors (heterocycles containing nitrogen). The higher oxidation states are stabilized by strong σ- and π-donors, such as O2− and N3−.

Despite its broad range of compounds in numerous oxidation states, osmium in bulk form at ordinary temperatures and pressures resists attack by all acids, including aqua regia but is attacked by fused alkalis.

Isotopes

Osmium has seven naturally occurring isotopes, six of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. 186Os undergoes alpha decay with such a long half-life (2.0±1.1)×1015 years, approximately 140000 times the age of the universe, that for practical purposes it can be considered stable. Alpha decay is predicted for all seven naturally occurring isotopes, but it has been observed only for 186Os, presumably due to very long half-lives. It is predicted that 184Os and 192Os can undergo double beta decay but this radioactivity has not been observed yet.

187Os is the descendant of 187Re (half-life 4.56×1010 years) and is used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. This decay is a reason why rhenium-rich minerals are abnormally rich in 187Os. However, the most notable application of osmium isotopes in geology has been in conjunction with the abundance of iridium, to characterise the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the non-avian dinosaurs 65 million years ago.

History

Osmium was discovered in 1803 by Smithson Tennant and William Hyde Wollaston in London, England. The discovery of osmium is intertwined with that of platinum and the other metals of the platinum group. Platinum reached Europe as platina ("small silver"), first encountered in the late 17th century in silver mines around the Chocó Department, in Colombia. The discovery that this metal was not an alloy, but a distinct new element, was published in 1748. Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue. Joseph Louis Proust thought that the residue was graphite. Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed iridium in the black platinum residue in 1803, but did not obtain enough material for further experiments. Later the two French chemists Antoine-François Fourcroy and Nicolas-Louis Vauquelin identified a metal in a platinum residue they called ‘ptène’.

In 1803, Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids and obtained a volatile new oxide, which he believed was of this new metal—which he named ptene, from the Greek word πτηνος (ptènos) for winged. However, Tennant, who had the advantage of a much larger amount of residue, continued his research and identified two previously undiscovered elements in the black residue, iridium and osmium. He obtained a yellow solution (probably of cis–[Os(OH)2O4]2−) by reactions with sodium hydroxide at red heat. After acidification he was able to distill the formed OsO4. He named it osmium after Greek osme meaning "a smell", because of the ashy and smoky smell of the volatile osmium tetroxide. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.

Uranium and osmium were early successful catalysts in the Haber process, the nitrogen fixation reaction of nitrogen and hydrogen to produce ammonia, giving enough yield to make the process economically successful. At the time, a group at BASF led by Carl Bosch bought most of the world's supply of osmium to use as a catalyst. Shortly thereafter, in 1908, cheaper catalysts based on iron and iron oxides were introduced by the same group for the first pilot plants, removing the need for the expensive and rare osmium.

Nowadays osmium is obtained primarily from the processing of platinum and nickel ores.

Occurrence

Native platinum containing traces of the other platinum group metals
 
Osmium is one of the even-numbered elements, which puts it in the upper half of elements commonly found in space. It is, however, the least abundant stable element in Earth's crust, with an average mass fraction of 50 parts per trillion in the continental crust.

Osmium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium (osmium rich), and iridosmium (iridium rich). In nickel and copper deposits, the platinum group metals occur as sulfides (i.e., (Pt,Pd)S)), tellurides (e.g., PtBiTe), antimonides (e.g., PdSb), and arsenides (e.g., PtAs2); in all these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, osmium can be found naturally in alloys with nickel or copper.

Within Earth's crust, osmium, like iridium, is found at highest concentrations in three types of geologic structure: igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld Igneous Complex in South Africa, though the large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin in Canada are also significant sources of osmium. Smaller reserves can be found in the United States. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. The second large alluvial deposit was found in the Ural Mountains, Russia, which is still mined.

Production

 
Osmium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper and nickel, noble metals such as silver, gold and the platinum group metals, together with non-metallic elements such as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting material for their extraction. Separating the metals requires that they first be brought into solution. Several methods can achieve this, depending on the separation process and the composition of the mixture. Two representative methods are fusion with sodium peroxide followed by dissolution in aqua regia, and dissolution in a mixture of chlorine with hydrochloric acid. Osmium, ruthenium, rhodium and iridium can be separated from platinum, gold and base metals by their insolubility in aqua regia, leaving a solid residue. Rhodium can be separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os and Ir, is treated with sodium oxide, in which Ir is insoluble, producing water-soluble Ru and Os salts. After oxidation to the volatile oxides, RuO
4
is separated from OsO
4
by precipitation of (NH4)3RuCl6 with ammonium chloride. 

After it is dissolved, osmium is separated from the other platinum group metals by distillation or extraction with organic solvents of the volatile osmium tetroxide. The first method is similar to the procedure used by Tennant and Wollaston. Both methods are suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgy techniques.

Neither the producers nor the United States Geological Survey published any production amounts for osmium. In 1971, estimations of the United States production of osmium as a byproduct of copper refining was 2000 troy ounces (62 kg). In 2017, the estimated US import of osmium for consumption was 90 kg.

Applications

Because of the volatility and extreme toxicity of its oxide, osmium is rarely used in its pure state, but is instead often alloyed with other metals for high-wear applications. Osmium alloys such as osmiridium are very hard and, along with other platinum-group metals, are used in the tips of fountain pens, instrument pivots, and electrical contacts, as they can resist wear from frequent operation. They were also used for the tips of phonograph styli during the late 78 rpm and early "LP" and "45" record era, circa 1945 to 1955. Osmium-alloy tips were significantly more durable than steel and chromium needle points, but wore out far more rapidly than competing, and costlier, sapphire and diamond tips, so they were discontinued.

Osmium tetroxide has been used in fingerprint detection and in staining fatty tissue for optical and electron microscopy. As a strong oxidant, it cross-links lipids mainly by reacting with unsaturated carbon–carbon bonds and thereby both fixes biological membranes in place in tissue samples and simultaneously stains them. Because osmium atoms are extremely electron-dense, osmium staining greatly enhances image contrast in transmission electron microscopy (TEM) studies of biological materials. Those carbon materials otherwise have very weak TEM contrast (see image). Another osmium compound, osmium ferricyanide (OsFeCN), exhibits similar fixing and staining action.

The tetroxide and its derivative potassium osmate are important oxidants in organic synthesis. For the Sharpless asymmetric dihydroxylation, which uses osmate for the conversion of a double bond into a vicinal diol, Karl Barry Sharpless was awarded the Nobel Prize in Chemistry in 2001. OsO4 is very expensive for this use, so KMnO4 is often used instead, even though the yields are less for this cheaper chemical reagent. 

In 1898 an Austrian chemist Auer von Welsbach developed the Oslamp with a filament made of osmium, which he introduced commercially in 1902. After only a few years, osmium was replaced by the more stable metal tungsten. Tungsten has the highest melting point among all metals, and its use in light bulbs increases the luminous efficacy and life of incandescent lamps.

The light bulb manufacturer Osram (founded in 1906, when three German companies, Auer-Gesellschaft, AEG and Siemens & Halske, combined their lamp production facilities) derived its name from the elements of osmium and Wolfram (the latter is German for tungsten).

Like palladium, powdered osmium effectively absorbs hydrogen atoms. This could make osmium a potential candidate for a metal-hydride battery electrode. However, osmium is expensive and would react with potassium hydroxide, the most common battery electrolyte.

Osmium has high reflectivity in the ultraviolet range of the electromagnetic spectrum; for example, at 600 Å osmium has a reflectivity twice that of gold. This high reflectivity is desirable in space-based UV spectrometers, which have reduced mirror sizes due to space limitations. Osmium-coated mirrors were flown in several space missions aboard the Space Shuttle, but it soon became clear that the oxygen radicals in the low Earth orbit are abundant enough to significantly deteriorate the osmium layer.

The only known clinical use of osmium is synovectomy in arthritic patients in Scandinavia. It involves the local administration of osmium tetroxide (OsO4), which is a highly toxic compound. The lack of reports of long-term side effects suggest that osmium itself can be biocompatible, though this depends on the osmium compound administered. In 2011, osmium(VI) and osmium(II) compounds were reported to show anticancer activity in vivo, it indicated a promising future for using osmium compounds as anticancer drugs.

Precautions

Metallic osmium is harmless but finely divided metallic osmium is pyrophoric and reacts with oxygen at room temperature, forming volatile osmium tetroxide. Some osmium compounds are also converted to the tetroxide if oxygen is present. This makes osmium tetroxide the main source of contact with the environment. 

Osmium tetroxide is highly volatile and penetrates skin readily, and is very toxic by inhalation, ingestion, and skin contact. Airborne low concentrations of osmium tetroxide vapor can cause lung congestion and skin or eye damage, and should therefore be used in a fume hood. Osmium tetroxide is rapidly reduced to relatively inert compounds by e.g. ascorbic acid or polyunsaturated vegetable oils (such as corn oil).

Price

Osmium is usually sold as a minimum 99.9% pure powder. Like other precious metals, it is measured by troy weight and by grams.The market price of osmium has not changed in decades, primarily because little change has occurred in supply and demand. In addition to so little of it being available, osmium is difficult to work with, has few uses, and is a challenge to store safely because of the toxic compound it produces when it oxidizes. 

While the price of $400 per troy ounce has remained steady since the 1990s, inflation since that time has led to the metal losing about one-third of its value in the two decades prior to 2019.

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