Palladium Monosulphide, PdS

Palladous Sulphide, Palladium Monosulphide, PdS, results on heating together sulphur and ammonium chlor-palladate; it is also formed by passing pure hydrogen sulphide over palladosammine chloride at 70° to 80° C. The mass becomes black, and at higher temperatures ammonium chloride volatilises, leaving a residue, insoluble in individual mineral acids, but soluble in mixtures such as aqua regia.

As obtained in either of the foregoing ways, palladous sulphide is a hard, metallic-looking substance, melting at approximately 950° C., and insoluble in all ordinary solvents.

On passing hydrogen sulphide through a solution of a palladous salt, a dark brown precipitate is obtained, which is presumably another form of palladous sulphide.5 It is insoluble in ammonium sulphide and in hydrochloric acid, but it dissolves both in nitric acid and in aqua regia. When heated in air, a basic sulphate is produced, whilst in chlorine palladous chloride is formed. Potassium cyanide gradually effects its solution. With sulphides of the alkali metals, sulpho- or thio-palladites, M₂Pd₃S₄, are formed.