Barium Thiophosphates

Several barium phosphates in which the oxygen has been partially or wholly replaced by sulphur have been separated. Barium trithiophosphate, Ba₃(PS₃O)₂.20H₂O, is obtained by the action of a solution of barium sulphide on sodium tetrathiophosphate. It is stable when dry, but is decomposed by water or dilute acids with the evolution of sulphuretted hydrogen. By substituting barium hydrogen sulphide for the sulphide, the compound Ba₃(PS₂O₂)₂.18H₂O, or 8H₂O, is formed. By the action of excess of barium sulphide on phosphorus pentasulphide the compound Ba₃(PS₄)₂.aq. has been prepared in microscopic needles.