Osmium, 6 cycles Ⅷ group element periodic table, a member of platinum group metals. Element symbol Os, atomic number 76, relative atomic mass 190.2, belongs to heavy platinum group metal, which is the densest metal known at present.
Osmium platinum. Platinum-based elements almost completely exist in the elemental state and are highly dispersed in various ores, such as primary platinum ore, nickel sulfide copper ore, magnetite, etc. Platinum-based elements almost invariably co-exist to form natural alloys. In the ore containing platinum series elements, platinum is usually the main component, while the remaining platinum series elements, due to their small content, must be found through chemical analysis. Osmium, iridium, palladium, rhodium and ruthenium are all found in the residue of platinum extracted from platinum ore, because they are all composed of platinum ores. Platinum-based elements have stable chemical properties. Except for platinum and palladium, they are insoluble not only in ordinary acids but also in aqua regia. Palladium is also soluble in hot nitric acid. All platinum-based elements have a strong tendency to form coordination compounds.
Osmium metal elemental medium density is known, its density is 22.59 g/cm3, melting point 3045 ℃, boiling point at above 5300 ℃. Hexagonal dense lattice. Gray-blue metal, hard and brittle, in the iron mortar pound, it will be very easy to become a powder, osmium powder is blue-black, and osmium metal powder can be spontaneous combustion. The vapor of osmium has poisonous, can stimulate the eye ministry mucous membrane of the person strongly, can cause blindness badly.
The metal osmium is very stable in the air, the powdered osmium is easy to oxidize. Concentrated nitric acid, sulfuric acid, sodium hypochlorite solution can make its oxidation. Osmium oxide (OsO2) can be easily produced by reaction with oxygen at room temperature.
Osmium can be used as a catalyst in industry. Using osmium as catalyst for ammonia synthesis or hydrogenation can obtain high conversion rate at low temperature. If mixed with a little osmium in the platinum, it can be made into a hard and sharp osmium platinum alloy scalpel. The use of osmium and a certain amount of iridium can be made of osmiridium alloy, such as iridium pen nib that silver white dot that osmiridium alloy, osmiridium alloy hard wear resistant, can be used as a clock and important instrument bearings, long life.