Diammonium phosphate

Diammonium phosphate^[1]
Names
	IUPAC name diammonium hydrogen phosphate
	Other names ammonium monohydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate dibasic
Identifiers
CAS Number	7783-28-0 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:63051;
ChemSpider	22946 ;
ECHA InfoCard	100.029.079
E number	E342(ii) (antioxidants, ...)
PubChem CID	24540;
UNII	10LGE70FSU ;
CompTox Dashboard (EPA)	DTXSID6029705 ;
	InChI InChI=1S/2H3N.H3O4P/c;;1-5(2,3)4/h21H3;(H3,1,2,3,4) Key: MNNHAPBLZZVQHP-UHFFFAOYSA-N ; InChI=1/2H3N.H3O4P/c;;1-5(2,3)4/h21H3;(H3,1,2,3,4)/p-1 Key: MNNHAPBLZZVQHP-REWHXWOFAG;
	SMILES [NH4+].[NH4+].OP([O-])([O-])=O;
Properties
Chemical formula	(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
Solubility in water	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). verify (what is ?) Infobox references

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.

Solid diammonium phosphate shows a dissociation pressure of ammonia as given by the following expression and equation:^[2]

(NH₄)₂HPO₄(s) ⇌ NH₃(g) + (NH₄)H₂PO₄(s)

At 100 °C, the dissociation pressure of diammonium phosphate is approximately 5 mmHg.^[3]

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."

^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
^ John R Van Wazer (1958). Phosphorus And Its Compounds - Volume I: Chemistry. New York: Interscience Publishers, Inc. p. 503.
^ McKetta Jr, John J., ed. (1990). Encyclopedia of Chemical Processing and Design (Chemical Processing and Design Encyclopedia). New York: Marcel Dekker, Inc. p. 478. ISBN 0-8247-2485-2.

[hand-1] Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8

[2] John R Van Wazer (1958). Phosphorus And Its Compounds - Volume I: Chemistry. New York: Interscience Publishers, Inc. p. 503.

[3] McKetta Jr, John J., ed. (1990). Encyclopedia of Chemical Processing and Design (Chemical Processing and Design Encyclopedia). New York: Marcel Dekker, Inc. p. 478. ISBN 0-8247-2485-2.

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