Potassium Stibiothiosulphate, K₃Sb(S₂O₃)₃

Potassium Stibiothiosulphate, K₃Sb(S₂O₃)₃, forms silk-like, needle-shaped crystals resembling asbestos. It is very soluble in water, but decomposes on boiling, with formation of the orange-red oxysulphide Sb₆O₃S₆. The rubidium and barium salts have also been obtained. The salts of sodium, calcium and strontium exist only in solution. The potassium salt appears to have the constitution represented by the formula Sb[S.SO₂.OK]₃.

By the hydrolysis of these alkali stibiothiosulphates fairly stable sols of antimony pentasulphide may be obtained.