Phosphorus Oxysulphides

The compound P₄O₆S₄ was prepared by heating together P₄O₆ and sulphur in an atmosphere of nitrogen or carbon dioxide:—

P₄O₆ + 4S = P₄O₆S₄

It appears as colourless rectangular prisms which melt at about 102° C. and boil at 295° C. The vapour density is 11.8 to 12.5 (air =1), which corresponds to the formula given. It is very easily soluble in CS₂. In moist air it decomposes as follows:—

P₄O₆S₄ + 6H₂O = 4HPO₃ + 4H₂S

Another oxysulphide, also a derivative of P₂O₅, was produced when H₂S dissolved in POCl₃ containing carbon disulphide was allowed to react for some weeks at 0° C. Small needle-shaped crystals having the composition P₂O₂S₃ then separated. They melted at about 300° C. and sublimed in a vacuum with decomposition. The compound was decomposed by moist air with production of H₂S.

2POCl₃ + 3H₂S = P₂O₂S₃ + 6HCl