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Monosodium phosphate

Phosphorus, P  Oxygen, O  Hydrogen, H  Sodium, Na
Names
IUPAC name Sodium dihydrogen phosphate
Other names Monobasic sodium phosphate Sodium biphosphate
Identifiers
CAS Number	7558-80-7
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37585
ChEMBL	ChEMBL1368
ChemSpider	22626
ECHA InfoCard	100.028.591
E number	E339(i) (antioxidants, ...)
PubChem CID	24204
UNII	KH7I04HPUU
CompTox Dashboard (EPA)	DTXSID7035222
InChI InChI=1S/Na.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+1;/p-1Key: AJPJDKMHJJGVTQ-UHFFFAOYSA-M
SMILES .P(=O)(O)O
Properties
Chemical formula	NaH2PO4
Molar mass	119.976 g·mol
Appearance	White powder or crystals
Density	2.36 g/cm (anhydrous)
Solubility in water	59.90 g/(100 mL) (0°C)
Hazards
NFPA 704 (fire diamond)	0 0 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 , 100 kPa). N verify (what is  ?) Infobox references

Monosodium phosphate (MSP), also known as monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound with the chemical formula NaH₂PO₄. It is a sodium salt of phosphoric acid. It consists of sodium cations (Na) and dihydrogen phosphate anions (H₂PO−4). One of many sodium phosphates, it is a common industrial chemical. The salt exists in an anhydrous form, as well as monohydrate and dihydrate (NaH₂PO₄·H₂O and NaH₂PO₄·2H₂O respectively).

Production and reactions

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

Heating this salt above 169 °C gives disodium pyrophosphate:

2 NaH₂PO₄ → Na₂H₂P₂O₇ + H₂O

When heated at 550 °C, anhydrous trisodium trimetaphosphate is formed:

3 NaH₂PO₄ → Na₃P₃O₉ + 3 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. 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

1. ^ Schrödter, Klaus; Bettermann, Gerhard; Staffel, Thomas; Wahl, Friedrich; Klein, Thomas; Hofmann, Thomas (2008). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3. ISBN 978-3527306732.
2. Salaun, F.: "Influence of mineral environment on the buffering capacity of casein micelles" Archived 2012-03-13 at the Wayback Machine, "Milchwissenschaft", 62(1):3
3. Bell, R. N. (1950). "Sodium Metaphosphates". Inorganic Syntheses. Vol. 3. pp. 103–106. doi:10.1002/9780470132340.ch26. ISBN 9780470132340.

• Phosphates
• Sodium compounds
• Edible thickening agents