| Phosphine reacts with a solution of potassium in liquefied ammonia to form potassium dihydrophosphide, KH2P, white crystals decomposed by moist air with evolution of phosphine. On heating, it is converted into tripotassium phosphide, K3P. A solution of potassium in liquefied ammonia reacts with red phosphorus to form potassium pentaphosphide, KP5. The black product formed from potassium and phosphorus loses its excess of metal in vacuum at 400° to 450° C., yielding dipotassium pentaphosphide, K2P5. It is a lemon-yellow substance with a density of about 2, is unstable in air, and is decomposed by water with formation of solid phosphorus hydride. |