Monosodium phosphate
Ball-and-stick model of the dihydrogenphosphate anion
  Phosphorus, P
  Oxygen, O
  Hydrogen, H
  Sodium, Na
Names
IUPAC name
Sodium dihydrogen phosphate
Other names
  • Monobasic sodium phosphate
  • Sodium biphosphate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.028.591
E number E339(i) (antioxidants, ...)
UNII
  • InChI=1S/Na.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+1;/p-1 checkY
    Key: AJPJDKMHJJGVTQ-UHFFFAOYSA-M checkY
  • [Na+].[O-]P(=O)(O)O
Properties
NaH2PO4
Molar mass 119.976 g·mol−1
Appearance White powder or crystals
Density 2.36 g/cm3 (anhydrous)
59.90 g/(100 mL) (0°C)
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
0
0
0
Flash point Non-flammable
Related compounds
Other cations
Related compounds
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 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).[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 disodium pyrophosphate:

2 NaH2PO4 → Na2H2P2O7 + H2O

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

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.[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

  1. 1 2 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. Inorganic Syntheses. Vol. 3. pp. 103–106. doi:10.1002/9780470132340.ch26. ISBN 9780470132340.
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