| Tetraphosphorus Triselenide, P4Se3, is readily prepared by the action of yellow phosphorus on powdered selenium in boiling tetrahydronaphthalene. The crude substance crystallises from the solution and may be purified by extraction with a mixture of light petroleum and carbon disulphide. The colour of the selenide varies from yellow to orange-red, according to the thickness of the layer under observation. The density at 22° C. is 3.161. On being heated the selenide exhibits distinct phosphorescence above 160° C. and melts at about 242° C.; at 280° C. the phosphorescence is very marked. The compound is slowly decomposed by moisture, and reacts with alkali hydroxides, sulphides and carbonates to form alkali selenide. |