Monosodium phosphate

Monosodium phosphate

Names
IUPAC name Sodium dihydrogen phosphate
Other names anhydrous monobasic sodium phosphate sodium dihydrogen phosphate
Identifiers
CAS Number	7558-80-7 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:37585 Y
ChEMBL	ChEMBL1368 Y
ChemSpider	22626 Y
ECHA InfoCard	100.028.591
PubChem	24204
UNII	KH7I04HPUU N
InChI InChI=1S/Na.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+1;/p-1 Y Key: AJPJDKMHJJGVTQ-UHFFFAOYSA-M Y
SMILES [Na+].[O-]P(=O)(O)O
Properties
Chemical formula	NaH2PO4
Molar mass	119.98 g/mol
Appearance	White powder or crystals
Density	2.36 g/cm3 (anhydrous)
Solubility in water	59.90 g/100 mL (0°C)
Hazards
NFPA 704	0 1 0
Flash point	Non-flammable
Related compounds
Other cations	Monopotassium phosphate Monoammonium phosphate
Related compounds	Disodium phosphate Trisodium 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

Monosodium phosphate (MSP), also known as anhydrous monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound of sodium with dihydrogen phosphate (H₂PO₄⁻) anion. One of many sodium phosphates (such as NaPO3), it is a common industrial chemical. It exists as an anhydrous salt, as well as mono- and dihydrates.^[1]

Production and reactions

The salt is obtained by partial neutralization of phosphoric acid. The pKa of monosodium phosphate is 6.8-7.2 (depending on the physicochemical characteristics during pKa determination).^[2]

Heating this salt above 169 °C gives the corresponding sodium acid pyrophosphate:

2 NaH₂PO₄ → Na₂H₂P₂O₇ + H₂O

Uses

Phosphates are often used in foods and in water treatment. The pH of such formulations is generally adjusted by mixtures of various sodium phosphates, such as this salt.^[1] The sodium chloride equivalent value, or E-Value, is 0.49. It is soluble in 4.5 parts water.

Food additive

It is added in animal feed, toothpaste, and evaporated milk. It is used as a thickening agent and emulsifier.

Detection of magnesium

Monosodium phosphate is used to detect the presence of magnesium ions in salts. Formation of a white precipitate on the addition of ammonium chloride, ammonium hydroxide and monosodium phosphate to an aqueous or dilute HCl solution of the salt indicates presence of magnesium ions.

Notes