Osmium Tetrachloride, OsCl₄

Osmium Tetrachloride, OsCl₄, is obtained as a reddish brown sublimate when metallic osmium is heated in chlorine (Berzelius) between 650° and 700° C.

When resublimed in chlorine it condenses into a black mass of the same composition. On volatilisation it yields a yellow vapour. It is neither hygroscopic nor soluble in the usual solvents, save the powerful oxidising acids. Water has no action upon it unless the two are left in contact for a prolonged period, when hydrolysis gradually sets in, hydrochloric acid and osmium dioxide resulting.