Palladium Disulphide, PdS₂

Palladic Sulphide, Palladium Disulphide, PdS₂, has been prepared by igniting at bright red heat a mixture of ammonium chlor-palladate (1 part) with sulphur (12 parts) and sodium hydroxide (12 parts). The chlor-palladate may be replaced by palladous sulphide. The product is treated first with alcohol and then with dilute hydrochloric acid, when the disulphide is left as a dark brown crystalline powder, which readily dissolves in aqua regia. Exposure to air does not affect it, but ignition in an inert gas causes the loss of sulphur. With sulphides of the alkali metals, double sulphides are formed, known generally as sulpho- or thio-palladates, and having the general formula M₂PdS₃.