Diammonium phosphate

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.

Diammonium phosphate
Names
IUPAC name
diammonium hydrogen phosphate
Other names
ammonium monohydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate dibasic
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.079
E number E342(ii) (antioxidants, ...)
PubChem CID
UNII
  • InChI=1S/2H3N.H3O4P/c;;1-5(2,3)4/h2*1H3;(H3,1,2,3,4) Y
    Key: MNNHAPBLZZVQHP-UHFFFAOYSA-N Y
  • InChI=1/2H3N.H3O4P/c;;1-5(2,3)4/h2*1H3;(H3,1,2,3,4)/p-1
    Key: MNNHAPBLZZVQHP-REWHXWOFAG
SMILES
  • [NH4+].[NH4+].OP([O-])([O-])=O
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 in alcohol, acetone and liquid ammonia
Refractive index (nD)
 1.52
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 −1566.91 kJ/mol
Hazards
NFPA 704 (fire diamond)
2
0
1
Flash point Non-flammable
Safety data sheet (SDS) ICSC 0217
Related compounds
Other anions
 Monoammonium phosphate
Triammonium phosphate
Other cations
 Disodium phosphate
Dipotassium phosphate
Related compounds
 Ammonium nitrate
Ammonium sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

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.

According to the diammonium phosphate MSDS 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 and monoammonium phosphate at around 70 °C (158 °F). At 155 °C (311 °F), DAP emits phosphorus oxides, nitrogen oxides and ammonia."

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