Triamidophosphoric Acid, PO(NH₂)₃

Triamidophosphoric Acid or Phosphoryl Triamide, PO(NH₂)₃, was prepared by passing dry ammonia into dry phosphoryl chloride. After washing out the ammonium chloride, an insoluble white powder was left, which was scarcely affected by dilute acids or alkalies, but was decomposed by fusion with potash.

The preparation of this compound has not been confirmed by other investigators.

In metaphosphoric acid, O(PO)OH, or its polymers such as dimetaphosphoric acid, , the hydroxyl may be replaced by -NH₂, and the =O by =NH, giving amidometaphosphoric acids and imidometaphosphoric or metaphosphimic acids.

The action of ammonia on phosphorus pentoxide at low temperatures yielded a substance, or mixture, which was easily soluble in water and in alcohol.

The composition of the product corresponded to the formula NH(PO)OH, which may be regarded as derived from (NH₂)₂PO(OH) by loss of ammonia. It may also be represented as phosphoryl hydroxylamine, (PO)NHOH. The soluble salts gave precipitates with salts of the heavy metals.

When the products of the action of ammonia on phosphorus pentachloride (q.v.) were well washed, the residue was found to have the empirical composition of a phosphoryl imidoamide, NH(PO)NH₂, of which it is probably a polymer. On heating this compound, or other amides of phosphoric acid, ammonia is lost and phosphonitril, PNO, is left, thus

NH(PO)NH₂ = PNO + NH₃

This is a white powder which fuses at a red heat giving a black glass. It is not affected by aqueous acids and alkalies, nor even by hot nitric acid, but may be hydrolysed by fusion with caustic alkalies. On account of these properties it is represented as a polymer (PNO)_n of high molecular weight and probably cyclic structure.