Osmium is a member of the platinum group of metals and is commonly found in conjunction with these elements. The mixed metals can be extracted from the ore with aqua regia, followed by treatment of the soluble and insoluble portions in various ways. Osmium is found in both portions and is removed as the volatile tetroxide, which can then be reduced. Pure osmium is silver in colour and is the densest of all metals. It has a pungent smell, due to the formation of osmium tetroxide. Applications for osmium include its use as an alloying constituent with other group metals, the resultant alloys being extremely hard (e.g. osmiridium, a naturally occuring alloy of osmium and iridium which is extremely hard and is used for the tips of pen nibs). Osmium can also be used as a powerful catalyst in gas reactions.


1803 by Smithson Tennant in London, England.

10-4 ppm in the earth’s crust.

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Atomic number 76 Clip
Atomic / Molecular Weight 190.2 gmol-1Clip
Density 22580 kgm-3Clip
Lattice constant 273 fmClip
Melting Point 3303 KClip
Boiling Point 5273 KClip
Specific heat capacity 130 Jkg-1K-1Clip
Thermal conductivity 88 Wm-1K-1Clip
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See also: Osmiridium, Periodic Table, Platinum.

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Subjects: Chemistry