What is "diammonium phosphate"

Diammonium phosphate (DAP) (chemical formula (NH)HPO, IUPAC name diammonium hydrogen phosphate) is one of a series of water- soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid. Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:

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(NH)HPO(s) NH(g) + NHHPO(s)

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log P = −3063 / T + 175 log T + 3.3

where:

P = the resultant dissociation pressure of ammonia T = absolute temperature (K)

At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.