Contents

Monosodium phosphate

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 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37585 Y
ChEMBL	ChEMBL1368 Y
ChemSpider	22626 Y
ECHA InfoCard	100.028.591
E number	E339(i) (antioxidants, ...)
PubChem CID	24204
UNII	KH7I04HPUU N
CompTox Dashboard (EPA)	DTXSID7035222
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	119.976 g·mol−1
Appearance	White powder or crystals
Density	2.36 g/cm3 (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 [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chemical compound

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 saltofphosphoric 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).^[1]

Production and reactions[edit]

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).^[2]

Heating this salt above 169 °C gives disodium pyrophosphate:

2 NaH₂PO₄ → Na₂H₂P₂O₇ + H₂O

When heated at 550 °C, anhydrous trisodium trimetaphosphate is formed:^[3]

3 NaH₂PO₄ → Na₃P₃O₉ + 3 H₂O

Uses[edit]

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.^{[clarification needed]} It is soluble in 4.5 parts water.^{[clarification needed]}

Food additive[edit]

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

Detection of magnesium[edit]

Monosodium phosphate is used to detect the presence of magnesium ionsinsalts. 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[edit]