Ammonium phosphate

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Ammonium phosphate[1]
Ammonium phosphate.png
Ball-and-stick model of three ammonium cations and one phosphate anion
IUPAC name
ammonium phosphate
Other names
triammonium phosphate
3D model (JSmol)
ECHA InfoCard 100.030.709
EC Number 269-789-9
Molar mass 149 g/mol
Appearance White, tetrahedral crystals
58.0 g/100 mL (25 °C)
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Warning
H302, H319
P264, P270, P280, P301+312, P305+351+338, P330, P337+313, P501
NFPA 704
Flammability code 0: Will not burn. E.g., waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
−1671.9 kJ/mol
Related compounds
Other cations
Trisodium phosphate
Tripotassium phosphate
Related compounds
Diammonium phosphate
Monoammonium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Ammonium phosphate is the salt of ammonium and phosphate. It is a highly unstable compound with the formula (NH4)3PO4. Because of its instability, it is elusive and of no commercial value. A related "double salt", (NH4)3PO4.(NH4)2HPO4 is also recognized but is too unstable for practical use. Both triammonium salts evolve ammonia. In contrast to the fragile nature of the triammonium salts, diammonium phosphate (NH4)2HPO4 is a valuable material, mainly as a fertilizer. Also of value is monoammonium salt (NH4)H2PO4 which is also valued as a fertilizer. These two salts provide plants with fixed nitrogen and phosphorus.[2]

Preparation of triammonium phosphate[edit]

Triammonium phosphate can be prepared in the laboratory by treating 85% phosphoric acid with 30% ammonia solution:[3]

H3PO4 + 3 NH3 → (NH4)3PO4

(NH4)3PO4 is a colorless, crystalline solid. The solid, which has the odor of ammonia, is readily soluble in water. The salt converts to diammonium hydrogen phosphate (NH4)2HPO4.

Preparation of diammonium hydrogen phosphate (DAP)[edit]

DAP is a simple salt and a complex fertilizer.[4][5] It is also the source of nitrogen and phosphorus nutrients.[4][5]

H3PO4 + 2 NH3 → (NH4)2HPO4

On heating, (NH4)2 HPO4 evolves ammonia, giving colorless crystals of the monoammonium salt.

(NH4)2 HPO4 is a colorless, odorless, crystalline solid, which insoluble in water.[4]

See also[edit]


  1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–42, 5–19. ISBN 0-8493-0594-2.
  2. ^ Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in Ullmann’s Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_465.pub3
  3. ^ Smith, R. J.; Bryant, R. G. (1975-10-27). "Metal substitutions incarbonic anhydrase: a halide ion probe study". Biochemical and Biophysical Research Communications. 66 (4): 1281–1286. ISSN 0006-291X. PMID 3.
  4. ^ a b c Benckiser, R. Missing or empty |title= (help)
  5. ^ a b Ross, Wm. H.; Merz, Albert R.; Jacob, K. D. (March 1929). "Preparation and Properties of the Ammonium Phosphates". Industrial & Engineering Chemistry. 21 (3): 286–289. doi:10.1021/ie50231a029. ISSN 0019-7866.