Osmium Information
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Osmium Element
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.[3] The
element's abundance in the Earth's crust is among the rarest.
Pure osmium metal does not occur in nature. Osmium has a low
crustal abundance of about 0.001 part per million. Though rare, osmium is found
in native alloys with other platinum metals: in siserskite (up to 80 percent),
in iridosmine, in aurosmiridium (25 percent), and in slight amounts in native
platinum. Processes for isolating it are an integral part of the metallurgical
art that applies to all platinum metals.
The English chemist Smithson Tennant discovered the element
together with iridium in the residues of platinum ores not soluble in aqua
regia. He announced its isolation (1804) and named it for the unpleasant odour
of some of its compounds (Greek osme, odour).
Of the platinum metals, osmium is the most rapidly attacked by
air. The powdered metal, even at room temperature, exudes the characteristic
odour of the poisonous, volatile tetroxide, OsO4. Because solutions of OsO4 are
reduced to the black dioxide, OsO2, by some biological materials, it is
sometimes used to stain tissues for microscopic examinations.
Osmium is one of the densest elements in the world. It is a
lustrous, bluish white, hard metal and can be brittle even at a high
temperature. Within the platinum group, osmium has the highest melting point
and the lowest vapor pressure. Osmium tetroxide is a highly toxic powerful
oxidizing agent with a strong odor
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