Zinc Thioarsenates

Zinc Orthothioarsenate, Zn₃(AsS₄)₂, is precipitated in yellow flakes from a cold solution of zinc sulphate by addition of an alkali orthothioarsenate. Zinc pyrothioarsenate, Zn₂As₂S₇, is also obtained by double decomposition. Zinc meta-thioarsenate, Zn(AsS₃)₂, is precipitated when hydrogen sulphide is passed into a solution containing zinc in the presence of an excess of arsenic acid and of sulphuric or hydrochloric acid; under these conditions the precipitation is quantitative.