New crystal data for silver sulphide sulphate, Ag₈S₃SO₄

The title compound was recognized from the new and unexpected powder pattern of aged precipitates obtained by mixing solutions of excess silver nitrate and sodium thiosulphate under specified conditions. The possible crystalline impurities were identified and conditions were established to yield a pure product. The brown microcrystalline material is tetragonal with a = b = 7.201; c = 10.220 Å. It is a solid electrolyte, has an irreversible transition point at 246°C and melts at 405°C. Method of preparation and powder data are given.