Chemical Properties of Osmium
Osmium oxidises when heated in air. The oxidation of the powdered metal begins at temperatures below 212° C. in air, and below 170° C. in oxvgen, volatile vapours of the tetroxide, OsO4, being evolved. These vapours are intensely poisonous, producing temporary blindness and other unpleasant symptoms. Osmium is also oxidised when heated in steam. It is readily dissolved by fuming nitric acid, and by aqua regia unless the osmium has previously been strongly heated.
Fluorine is without action in the cold, but upon warming combination takes place. Chlorine attacks osmium at high temperatures, the tetrachloride, OsCl4, resulting at 650° to 700° C. Bromine vapour, however, is without action upon the metal.
When fused with a mixture of peroxide and nitrate of barium or sodium, osmium is dissolved.
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