Diammonium phosphate (DAP)
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.
Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:
- (NH4)2HPO4(s) ⇌ NH3(g) + (NH4)H2PO4(s)
At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.
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Product Info
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| Names | |
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| IUPAC name
diammonium hydrogen phosphate
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| Other names
ammonium monohydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate dibasic
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| Identifiers | |
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3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.029.079 |
| E number | E342(ii) (antioxidants, …) |
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PubChem CID
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| UNII | |
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CompTox Dashboard (EPA)
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| Properties | |
| (NH4)2HPO4 | |
| Molar mass | 132.06 g/mol |
| Appearance | colorless monoclinic crystals |
| Density | 1.619 g/cm3 |
| Melting point | 155 °C (311 °F; 428 K) decomposes |
| 57.5 g/100 mL (10 °C) 106.7 g/100 mL (70 °C) |
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| Solubility | insoluble in alcohol, acetone and liquid ammonia |
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Refractive index (nD)
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1.52 |
| Thermochemistry | |
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Std enthalpy of
formation (ΔfH⦵298) |
−1566.91 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Safety data sheet (SDS) | ICSC 0217 |
| Related compounds | |
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Other anions
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Monoammonium phosphate Triammonium phosphate |
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Other cations
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Disodium phosphate Dipotassium phosphate |
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Related compounds
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Ammonium nitrate Ammonium sulfate |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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