Ammonium phosphate is the salt of ammonia and phosphoric acid. It has the formula (NH4)3PO4 and consists of ammonium cations and phosphate anion. It is obtained as a crystalline powder upon mixing concentrated solutions of ammonia and phosphoric acid. It is soluble in water, and the aqueous solution on boiling loses ammonia. There are related acid salts, diammonium phosphate (DAP, (NH4)2HPO4) and monoammonium phosphate (MAP, NH4H2PO4). These can be interconverted by adding more ammonia or phosphoric acid as needed.
Ammonium phosphate is used as an ingredient in some fertilizers as a source of nitrogen. It is also used as a flame retardant in thermoplastic compositions. It is also used in bread making to promote the growth of the yeast.