Strontium Thioarsenates

Strontium Orthothioarsenate, Sr₃(AsS₄)₂.nH₂O, may be prepared by digesting strontium sulphide with an aqueous solution of strontium pyrothioarsenate and, after filtering, either adding alcohol or evaporating to crystallisation. Strontium pyrothioarsenate, Sr₂As₂S₇.nH₂O, is obtained by mixing aqueous solutions of a strontium salt and sodium pyrothioarsenate, and evaporating the liquid. Both salts resemble the analogous calcium salts in properties. A crystalline double salt containing orthothioarsenate and pyrothioarsenite, and of composition Sr₃(AsS₄)₂.Sr₂As₂S₅.8H₂O, has been obtained by evaporating in vacuo a saturated solution of arsenic pentasulphide in aqueous strontium hydrosulphide.