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Diammonium phosphate
Diammonium phosphate (DAP; IUPAC name diammonium hydrogen phosphate; chemical formula (NH4)2(HPO4) is one of a series of water-soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid.
Diammonium phosphate[1]NamesIUPAC name
diammonium hydrogen phosphate
Other names
ammonium monohydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate dibasic
Properties
Chemical formula
(NH4)2HPO4Molar mass132.06 g/molAppearancecolorless monoclinic crystalsDensity1.619 g/cm3Melting point155 °C (311 °F; 428 K) decomposes
Solubility in water
57.5 g/100 mL (10 °C)
106.7 g/100 mL (70 °C)Solubilityinsoluble
Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:[2]
(NH4)2HPO4(s) ⇌ NH3(g) + (NH4)H2PO4(s)
At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.[3]