Uranous Phosphide, U₃P₄

Uranous Phosphide, U₃P₄, is obtained in the form of a black microcrystalline powder by fusing together sodium uranous chloride and aluminium phosphide at 1000° C. in a stream of hydrogen; or by the aluminothermie process, using a mixture containing phosphorus and uranyl pyrophosphate or a higher oxide of uranium. Both processes yield a product contaminated with aluminium, which is difficult to remove. A purer crystalline product is obtained by the action of phosphine on sodium uranous chloride, but in this case the yield is poor. The phosphide is slowly oxidised in air to yellow uranyl phosphate. It is slowly decomposed by water, rapidly by nitric acid.