Ammonium phosphate

Ammonium phosphate. The normal phosphate, (NH4)3PO4, is obtained as a crystalline powder, on mixing concentrated solutions of ammonia and phosphoric acid, or on the addition of excess of ammonia to the acid phosphate (NH4)2HPO4. It is soluble in water, and the aqueous solution on boiling loses ammonia and the acid phosphate NH4H2PO4 is formed. It is used as an ingredient in some fertilizers as a high source of elemental nitrogen, composing of 34% of total mass.

Diammonium hydrogen phosphate, or diammonium phosphate, (NH4)2HPO4, is formed by evaporating a solution of phosphoric acid with excess of ammonia. It crystallizes in large transparent prisms, which melt on heating and decompose, leaving a residue of metaphosphoric acid, (HPO3).

Ammonium dihydrogen phosphate, or monoammonium phosphate, NH4&bull;H2PO4, is formed when a solution of phosphoric acid is added to ammonia until the solution is distinctly acid. It crystallizes in quadratic prisms. Monoammonium phosphate is often used in the blending of dry agricultural fertilizers. It supplies soil with elemental nitrogen at 11% of total mass and phosphorus at 52%. The compound is also a component of the ABC powder in some dry powder fire extinguishers.