Osmium and iridium were discovered in 1803 by British chemist Smithson Tennant in the black residue remaining after dissolving platinum ore with aqua regia. Osmium is a hard, brittle, blue-gray metal that is difficult to produce in pure form due to its tendency to form toxic osmium tetroxide when exposed to air. It is primarily used to make very hard alloys for applications requiring minimal frictional wear such as pen tips and electrical contacts. Turkey has the world's largest reserves of osmium.

2. 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

3. 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.

5. 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

6. 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.

7. Compound
 Fluorides
 Osmium hexafluoride: OsF6
 Osmium octafluoride: OsF8
 Osmium tetrafluoride: OsF4
 Osmium heptafluoride: OsF7
 Osmium pentafluoride: [OsF5]4

8. Continue…
 Chlorides
 Osmium trichloride3
 Osmium tetrachloride: OsCl4
 Osmium pentachloride: OsCl5
 Bromides
 Osmium tetrabromide: OsBr4

9. 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)

10. Continue…
 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)

11. 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.