Osmium Tetrasulphide, OsS₄

Osmium Tetrasulphide, OsS₄, is obtained as a brown precipitate when hydrogen sulphide is passed through an acidified aqueous solution of the tetroxide. It is not affected by solutions of the hydroxides or sulphides of the alkali metals, in which it is insoluble. It oxidises readily in the air, and at high temperatures it decomposes, yielding the free metal. When gently heated in vacuo it is stated to yield a sulphide of composition Os₂S₅.