Zinc Thiophosphates

Zinc thio-orthophosphate, Zn₃(PS₄)₂, is obtained by heating zinc chloride and phosphorus pentasulphide together. It is a white crystalline powder that, when heated in the absence of air, decomposes into phosphoric and zinc sulphides. It can be purified by dilute hydrochloric acid but dissolves in the concentrated acid.

Pale yellow crystalline masses mixed with phosphorus pentasulphide are obtained by heating zinc, phosphorus, and sulphur together. Zinc thiohypophosphate, Zn₂P₂S₆, was obtained in transparent yellow plates, apparently hexagonal, of density 2.2, by heating the above mixture in sealed tubes imbedded in iron tubes filled with sand.

Though it is insoluble it slowly decomposes in water or moisture with the evolution of hydrogen sulphide. Nitric acid attacks it violently, but hydrochloric acid has no action.

Zinc thiopyrophosphate has been prepared in small crystalline needles, rapidly decomposed by water or moist air, by a similar method. The crystals are clear yellow, and are attacked violently by cold nitric acid.