Uranium Oxysulphide, U₃O₂S₄

Uranium Oxysulphide, U₃O₂S₄ or UO₂.2US₂, is formed when uranous oxide, urano-uranic oxide, or ammonium uranate is heated in a stream of hydrogen sulphide or carbon disulphide vapour; when one of the oxides is heated with a mixture of ammonium chloride and sulphur; or when uranyl sulphate is heated in hydrogen or with potassium pentasulphide. It is a greyish-black powder, which is decomposed by nitric acid with deposition of sulphur.