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| Names | |
|---|---|
| IUPAC name diammonium hydrogen phosphate | |
| Other names ammonium monohydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate dibasic | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
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| ECHA InfoCard | 100.029.079 |
| E number | E342(ii)(antioxidants, ...) |
| UNII | |
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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) | |
| Solubility | insoluble inalcohol,acetone and liquidammonia |
Refractive index (nD) | 1.52 |
| Thermochemistry | |
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 | |
Otheranions | Monoammonium phosphate Triammonium phosphate |
Othercations | Disodium phosphate Dipotassium phosphate |
Related compounds | Ammonium nitrate Ammonium sulfate |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Diammonium phosphate (DAP;IUPAC namediammonium hydrogen phosphate; chemical formula (NH4)2(HPO4)) is one of a series ofwater-solubleammonium phosphatesalts that can be produced whenammonia reacts withphosphoric acid.
Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:[2]
At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.[3]
According to the diammonium phosphateMSDS from CF Industries, Inc., decomposition starts as low as 70 °C: "Hazardous Decomposition Products: Gradually loses ammonia when exposed to air at room temperature. Decomposes to ammonia andmonoammonium phosphate at around 70 °C (158 °F). At 155 °C (311 °F), DAP emits phosphorus oxides,nitrogen oxides and ammonia."
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DAP is used as afertilizer.[4] When applied as plant fertilizer, it temporarily increases thesoilpH, but over a long term the treated ground becomes moreacidic than before, upon nitrification of the ammonium. It is incompatible withalkaline chemicals because itsammonium ion is more likely to convert toammonia in a high-pH environment. The average pH in solution is 7.5–8.[5] The typicalNPK ratio is 18-46-0 (18% N, 46% P2O5, 0% K2O).[5]
DAP can be used as afire 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.[6] These are important effects in fightingwildfires as lowering thepyrolysis temperature and increasing the amount ofchar formed reduces that amount of available fuel and can lead to the formation of afirebreak.
DAP is also used as ayeast nutrient in winemaking andmead-making; as an additive in some brands of cigarettes purportedly as anicotine enhancer; to prevent afterglow in matches, in purifyingsugar; as aflux for soldering tin, copper, zinc and brass; and to controlprecipitation of alkali-soluble and acid-insoluble colloidal dyes onwool.[1]
The compound occurs in the nature as the exceedingly rare mineral phosphammite.[7][8] The related dihydrogen compound occurs as the mineral biphosphammite.[9][8] Both are related to guano deposits.[7][9]
