| Diammonium phosphate[1] | |
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diammonium hydrogen phosphate |
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Other names
ammonium monohydrogen phosphate, ammonium phosphate dibasic |
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| Identifiers | |
| CAS number | 7783-28-0 |
| PubChem | 24540 |
| ChemSpider | 22946 |
| UNII | 10LGE70FSU |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | (NH4)2HPO4 |
| Molar mass | 132.07 g/mol |
| Appearance | white powder |
| Density | 1.619 g/cm3 |
| Melting point |
155 ºC decomp. |
| Solubility in water | 57.5 g/100 mL (10 ºC) 106.7 g/100 mL (100 °C) |
| Solubility | insoluble in alcohol, acetone and liquid ammonia |
| Refractive index (nD) | 1.52 |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
-1566.91 kJ/mol |
| Hazards | |
| MSDS | ICSC 0217 |
| EU Index | Not listed |
| NFPA 704 |
0
2
1
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| Flash point | Non-flammable |
| Related compounds | |
| Other anions | Monoammonium phosphate Triammonium phosphate |
| Other cations | Disodium phosphate Dipotassium phosphate |
| Related compounds | Ammonium nitrate Ammonium sulfate |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Diammonium phosphate (DAP) (chemical formula (NH4)2HPO4, IUPAC name diammonium hydrogen phosphate) is one of a series of water-soluble ammonium phosphate salts which 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:[2]
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where:
At 100ºC, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.[3]
DAP is used as a fertilizer. When applied as plant food, it temporarily increases the soil pH, but over a long term the treated ground becomes more acidic than before upon nitrification of the ammonium. It is incompatible with alkaline chemicals because its ammonium ion is more likely to convert to ammonia in a high-pH environment.
DAP can be used as a fire retardant. It lowers the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char.[4] These are important effects in fighting wildfires as lowering the pyrolysis temperature and increasing the amount of char formed reduces that amount of available fuel and can lead to the formation of a firebreak. It is the largest component of some popular commercial firefighting products.[5]
DAP is also used as a yeast nutrient in winemaking and brewing mead; as an additive in some brands of cigarettes purportedly as a nicotine enhancer; to prevent afterglow in matches, in purifying sugar; as a Flux for soldering tin, copper, zinc and brass; and to control precipitation of alkali-soluble and acid-insoluble colloidal dyes on wool. [1]