Ammonium Dihydrogen Phosphate - Wikipedia

Ammonium dihydrogen phosphate[1]

Names
IUPAC name Ammonium dihydrogen phosphate
Other names Monoammonium phosphate
Identifiers
CAS Number	7722-76-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:62982
ChemSpider	22812 Y
ECHA InfoCard	100.028.877
EC Number	231-764-5
E number	E342(i) (antioxidants, ...)
PubChem CID	24402
UNII	09254QB17T
CompTox Dashboard (EPA)	DTXSID5029689
InChI InChI=1S/H3N.H3O4P/c;1-5(2,3)4/h1H3;(H3,1,2,3,4) YKey: LFVGISIMTYGQHF-UHFFFAOYSA-N Y InChI=1/H3N.H3O4P/c;1-5(2,3)4/h1H3;(H3,1,2,3,4)Key: LFVGISIMTYGQHF-UHFFFAOYAX
SMILES [O-]P(=O)(O)O.[NH4+]
Properties
Chemical formula	H6NO4P
Molar mass	115.025 g·mol−1
Appearance	white crystals
Odor	none
Density	1.80 g/cm3
Melting point	190 °C (374 °F; 463 K)
Solubility in water	(g/dL) 28 (10 °C)36 (20 °C)44 (30 °C)56 (40 °C)66 (50 °C)81 (60 °C)99 (70 °C)118 (80 °C)173 (100 °C) [2][3]
Solubility	insoluble in ethanol[2] insoluble in acetone
Refractive index (nD)	1.525
Structure
Crystal structure	tetragonal
Thermochemistry
Std enthalpy offormation (ΔfH⦵298)	−1445.07 kJ/mol[4]
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H319
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)	1 0 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	5750 mg/kg (rat, oral)
Related compounds
Other anions	Ammonium phosphateDiammonium phosphate
Other cations	Monosodium phosphatePotassium dihydrogen phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chemical compound

Ammonium dihydrogen phosphate (ADP), also known as monoammonium phosphate (MAP)[5] is a chemical compound with the chemical formula (NH4)(H2PO4). ADP is a major ingredient of agricultural fertilizers[6] and dry chemical fire extinguishers.[7] It also has significant uses in optics[8] and electronics.[9]

Chemical properties

[edit]

Monoammonium phosphate is soluble in water and crystallizes from it as the anhydrous salt in the tetragonal system, as elongated prisms or needles.[8] It is practically insoluble in ethanol.[2]

Solid monoammonium phosphate can be considered stable in practice for temperatures up to 200 °C, when it decomposes into gaseous ammonia NH3 and molten phosphoric acid H3PO4.[10] At 125 °C the partial pressure of ammonia is 0.05 mm Hg.[11]

A solution of stoichiometric monoammonium phosphate is acidic (pH 4.7 at 0.1% concentration, 4.2 at 5%).[12]

Preparation

[edit]

Monoammonium phosphate is industrially prepared by the exothermic reaction of phosphoric acid and ammonia in the correct proportions:[13]

NH3 + H3PO4 → NH4H2PO4

Crystalline MAP then precipitates.

Uses

[edit]

Agriculture

[edit]

The largest use of monoammonium phosphate by weight is in agriculture, as an ingredient of fertilizers. It supplies soil with the elements nitrogen and phosphorus in a form usable by plants. Its NPK label is 12-61-0 (12-27-0), meaning that it contains 12% by weight of elemental nitrogen and (nominally) 61% of phosphorus pentoxide P2O5, or 27% of elemental phosphorus.

Fire extinguishers

[edit]

The compound is also a component of the ABC powder in some dry chemical fire extinguishers.

Optics

[edit]

Monoammonium phosphate is a widely used crystal in the field of optics due to its birefringence properties. As a result of its tetragonal crystal structure, this material has negative uniaxial optical symmetry with typical refractive indices no = 1.522 and ne = 1.478 at optical wavelengths.[8]

Electronics

[edit]

Monoammonium phosphate crystals are piezoelectric, a property required in some active sonar transducers (the alternative being transducers that use magnetostriction). In the 1950s ADP crystals largely replaced the quartz and Rochelle salt crystals in transducers because they are easier to work than quartz and, unlike Rochelle salt, are not deliquescent.[9]

Toys

[edit]

Being relatively non-toxic[citation needed], MAP is also a popular substance for recreational crystal growing, being sold as toy kits mixed with dyes of various colors.

Natural occurrence

[edit]

The compound appears in nature as the rare mineral biphosphammite. It is formed in guano deposits.[14][15] A related compound, that is the monohydrogen counterpart, is the even more scarce phosphammite.[16][17]

References

[edit]

1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–40. ISBN 0-8493-0594-2.
2. ^ a b c Dejun Xu, Xing Xiong, Lin Yang, Zhiye Zhang, and Xinlong Wang (2016): "Determination of the Solubility of Ammonium Dihydrogen Phosphate in Water-Ethanol System at Different Temperatures from 283.2 to 343.2 K". Journal of Chemincal Engineering Data, volume 61, issue 1, pages 78–82. doi:10.1021/acs.jced.5b00224
3. ^ Chemical Book: "Ammonium dihydrogen phosphate". Accessed on 2018-08-14.
4. ^ National Bureau of Standards. Selected Values of Chemical Thermodynamic Properties. Technical note 270-3. 1968 [1]
5. ^ "Monoammonium Phosphate (MAP)" (PDF). www.mosaicco.com. Archived from the original (PDF) on 17 November 2015. Retrieved 5 June 2015.
6. ^ IPNI. "Monoammonium Phosphate (MAP)" (PDF). www.ipni.net. International Plant Nutrition Institute. Retrieved 21 July 2014.
7. ^ "Safety Data Sheet - Kidde 90 Multi-Purpose ABC Dry Chemical" (PDF). Mebane, NC: Badger Fire Protection. 28 September 2023. Retrieved 7 July 2025.
8. ^ a b c Amnon Yariv, Pochi Yeh (1984). Optical Waves in Crystals. Wiley, Inc.
9. ^ a b Willem Hackmann (1984). Seek and Strike: Sonar, Anti-Submarine Warfare and the Royal Navy, 1914–1954. Her Majesty's Stationery Office. ISBN 0-11-290423-8.
10. ^ G. O. Guerrant and D. E. Brown (196): "Thermal Decomposition of High-Analysis Fertilizers Based on Ammonium Phosphate". Journal of Agricultural and Food Chemistry, volume 13, issue 6, pages 493-497. doi:10.1021/jf60142a002
11. ^ John R Van Wazer (1958). Phosphorus And Its Compounds - Volume I: Chemistry. New York: Interscience Publishers, Inc. p. 503.
12. ^ Haifa Chemicals Ltd.: "Mono-Ammonium Phosphate 12-61-0 Archived 15 October 2022 at the Wayback Machine". Product fact sheet, accessed on 2018-08-13.
13. ^ Martin Bäckman, Martin Gunnarsson, Linnea Kollberg, Martin Müller, and Simon Tallvod (2016): "Production of Monoammonium Phosphate at Yara AB Archived 18 November 2017 at the Wayback Machine". Technical Report, Lund University.
14. ^ "Biphosphammite".
15. ^ "List of Minerals". 21 March 2011.
16. ^ "Phosphammite".
17. ^ "List of Minerals". 21 March 2011.

v t e Ammonium salts
Inorganic salts	monatomic anions NH4F (NH4)2S NH4Cl (NH4)2Se NH4Br NH4I oxyanions NH4NO2 NH4NO3 CaNH4PO4 (NH4)2CO3 (NH4)4UO2(CO3)3 (NH4)HCO3 NH4H2AsO4 NH4BrO3 NH4ClO NH4OCN NH4B5O8 (NH4)3PO4 NH4PH2O2 (NH4)2HPO4 (NH4)H2PO4 NH4IO4 (NH4PO4)n(OH)2 NH4NaHPO4 (NH4)2SO3 (NH4)2SO4 (NH4)Al(SO4)2·12H2O (NH4)2Fe(SO4)2·6H2O NH4Fe(SO4)2·12H2O NH4SO3NH2 (NH4)HSO4 (NH4)2S2O8 (NH4)2S2O3 NH4ClO3 NH4ClO4 (NH4)2Mg(SO4)2 NH4VO3 Nd(NH4)2(NO3)5 (NH4)2CrO4 (NH4)2Cr2O7 NH4MnO4 (NH4)3AsO4 NH4BrO4 (NH4)2MoO4 (NH4)6Mo7O24 (NH4)3Mo12PO40 NH4IO3 (NH4)2Ce(NO3)6 (NH4)8Ce2(SO4)8·4H2O (NH4)10H2W12O42·4H2O NH4ReO4 (NH4)2SeO4 (NH4)2TeO4 other anions NH4BF4 NH4N3 NH4CN NH4[Au(CN)2] (NH4)HF2 (NH4)2SeBr6 (NH4)3AlF6 NH4SbF6 NH4AsF6 (NH4)3CrF6 (NH4)3FeF6 (NH4)3GaF6 (NH4)2GeF6 (NH4)3InF6 NH4NbF6 (NH4)2PtF6 (NH4)2ReF6 (NH4)2SnF6 NH4TaF6 (NH4)2UF6 (NH4)3VF6 (NH4)SiF6 (NH4)HS NH4SCN (NH4)2ZnCl4 (NH4)2MoS4 NH4I3 (NH4)2PtBr6 (NH4)2SnBr6 (NH4)2TeCl6 (NH4)2IrCl6 (NH4)2OsCl6 (NH4)2PtCl6 (NH4)2ReCl6 (NH4)2PdCl6 (NH4)2PbCl6 (NH4)3RhCl6 (NH4)2SeCl6 (NH4)2SnCl6 (NH4)4[Fe(CN)6] (NH4)3VS4 (NH4)2S5 (NH4)4[HgBr6] (NH4)2[PtI6] NH4AuCl4 (NH4)2PdCl4 (NH4)3AsS4 (NH4)2WS4 (NH4)2[PtCl4]
Organic salts	Aluminon Ammonium acetate Ammonium adipate Ammonium alginate Ammonium benzoate Ammonium bituminosulfonate Ammonium butyrate Ammonium carbamate Ammonium caprylate Ammonium cinnamate Ammonium citrate Ammonium diethyl dithiophosphate Ammonium ferric citrate Ammonium formate Ammonium fumarate Ammonium glutamate Ammonium heptadecanoate Ammonium itaconate Ammonium lactate Ammonium lauryl sulfate Ammonium laurate Ammonium malate Ammonium malonate Ammonium mandelate Ammonium myristate Ammonium nicotinate Ammonium nonanoate Ammonium oleate Ammonium oxalate Ammonium picrate Ammonium palmitate Ammonium perfluorononanoate Ammonium picolinate Ammonium propionate Ammonium salicylate Ammonium stearate Ammonium succinate Ammonium tartrate Ammonium thioglycolate Ammonium valerate Cupferron Ferric ammonium oxalate Murexide

v t e Phosphates

H3PO4[HPO4]2−[H2PO4]− He Li3PO4 Be3(PO4)2 BPO4+BO3 C (NH4)3PO4(NH4)2HPO4NH4H2PO4-N O +F Ne Na3PO4Na2HPO4NaH2PO4 Mg3(PO4)2 AlPO4 Si3(PO4)4 P +SO4-S Cl Ar K3PO4K2HPO4KH2PO4 Ca3(PO4)2 ScPO4 Ti VPO4VOPO4 CrPO4 Mn3(PO4)2MnPO4 Fe3(PO4)2FePO4 Co3(PO4)2 Ni3(PO4)2 Cu3(PO4)2 Zn3(PO4)2 GaPO4 Ge As -Se Br Kr Rb3PO4 Sr3(PO4)2 YPO4 Zr3(PO4)4 Nb Mo Tc Ru Rh Pd Ag3PO4 Cd3(PO4)2 InPO4 Sn SbPO4-SbO4 Te I Xe Cs3PO4 Ba3(PO4)2 * LuPO4 Hf Ta W Re Os Ir Pt AuPO4 Hg Tl3PO4 Pb3(PO4)2 BiPO4 Po At Rn Fr Ra ** Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og   * LaPO4 CePO4 PrPO4 NdPO4 PmPO4 SmPO4 EuPO4 GdPO4 TbPO4 DyPO4 HoPO4 ErPO4 TmPO4 YbPO4 ** AcPO4 Th3(PO4)4 Pa (UO2)3(PO4)2 (NpO2)3(PO4)2 PuPO4(PuO2)3(PO4)2HPuO2PO4 AmPO4 CmPO4 Bk Cf Es Fm Md No