Atomic number: 76
Year discovered: 1803
Discovered by: Smithson Tennant (1761-1815), a British chemist.
- Osmium was discovered, in 1803, by Smithson Tennant in the dark colored residue left when crude platinum was dissolved by aqua regia (a mixture of hydrochloric and nitric acid).
- This dark residue contains both osmium and iridium.
- Osmium metal is lustrous, bluish white, extremely hard, and brittle even at high temperatures.
- It has the highest melting point and lowest vapor pressure of the platinum group.
- The solid metal is not affected by air at room temperature, but the powdered or spongy metal slowly gives off osmium tetroxide, which is a powerful oxidizing agent and has a strong odor.
- Tetroxide is highly toxic and concentrations in air can cause lung congestion, skin damage, or eye damage.
- The industrial extraction of osmium is complex as the metal occurs in ores mixed with other metals such as ruthenium, rhodium, palladium, silver, platinum, and gold.
- Sometimes extraction of the precious metals such as iridium, rhodium, platinum and palladium is the main focus of a particular industrial operation while in other cases it is a by-product.
- The extraction is complex because of the presence of other metals and is only worthwhile because osmium is useful as a specialist metal and is the basis of some catalysts in industries.
- Because wires of the metal can be heated to high temperatures, they were used as filaments in early incandescent lamps; however, osmium was replaced by tungsten for this purpose.
- A hard alloy of osmium and iridium is used commercially for tips of fountain pens and phonograph needles.
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Information about other elements may be seen at this Chemical Elements List.
A special unit about words that include chemo-, chem- may be seen here.