Barium Thioarsenates

Normal barium orthothioarsenate, Ba₃As₂S₈.6H₂O, is formed by the action of barium hydrosulphide on arsenic pentasulphide as faintly yellow, thick, transparent needles. It is only slightly soluble in water, by which it is decomposed. When it is heated, water of crystallisation is given off and the colour deepens. At higher temperatures it is decomposed. A pyrothioarsenate has been isolated. There are also oxy-compounds, for example Ba₃(AsOS₃)₂.5H₂O, and Ba₃(AsO₃S)₂.6H₂O, Ba₃(AsO₂S₂)₂.7H₂O, and double salts, BaKAsS₄.6H₂O, BaNaAsO₃S.9H₂O, BaKAsOS₃. 7H₂O, and Ba₇Na₂As₅S₁₄O₇.12H₂O.