Date post: | 03-Aug-2015 |
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History Osmium and iridium were discovered at the same time by the
British chemist Smithson Tennant in 1803. Osmium and iridium were identified in the black residue remaining after dissolving platinum ore with aqua regia
Source
Obtained from the same ore with platinum.
Turkey, with 127,000 tonnes, has the world's largest reserves of osmium known.
Bulgaria also has large reserves of about 2500 tons.
These transition metals are also found in iridiosmium, a natural alloy of iridium and osmium, and platinum-bearing river sands in the Ural Mountains, North and South America.
Properties
Group Name: Platinum group
metal Block: Block D Period: 6
solid at 298 K
Colour: blue-gray
Boiling Point: 5285K (5012 ° C)
Melting Point: 3306K (3033 ° C)
Density : 22.61g / cm3
How to get
Metallic osmium is hard, brittle and very difficult to make.
Powdered osmium is easier to make but emits osmium tetroxide (OsO4) when it is exposed to the air. Unfortunately, osmium tetroxide smells bad and is very poisonous. Because of these problems, osmium is primarily used to make very hard alloys. Osmium alloys can be found in ball point pen tips, fountain pen tips, record player needles, electrical contacts and other devices where frictional wear must be minimized.
Compound
Fluorides
Osmium hexafluoride: OsF6
Osmium octafluoride: OsF8
Osmium tetrafluoride: OsF4
Osmium heptafluoride: OsF7
Osmium pentafluoride: [OsF5]4
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Chlorides Osmium trichloride3
Osmium tetrachloride: OsCl4 Osmium pentachloride: OsCl5 Bromides
Osmium tetrabromide: OsBr4
Reaction
Reaction of osmium with air
Osmium is largely immune to atmospheric attack. On heating with oxygen, osmium metal gives the rather volatile (melting point 30°C, boiling point 130°C) osmium (VIII) oxide, OsO4. Apparently, in air, finely divided osmium metal gives off a characteristic smell of OsO4 - bad news given that OsO4 is highly toxic.
Os(s) + 2O2(g) → OsO4(s)
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Reaction of osmium with water
Osmium does not react with water under normal conditions.
Reaction of osmium with the halogens
Osmium reacts with excess of fluorine, F2, at 600°C and 400 atmosphere pressure to form osmium(VII) fluoride, OsF7.
2Os(s) + 7F2(g) → 2OsF7(s) (yellow)
Application
Osmium has only a few uses. It is used to produce very hard alloys for fountain pen tips, instrument pivots, needles and electrical contacts. It is also used in the chemical industry as a catalyst.