Monosodium phosphate

Monosodium phosphate
Names
IUPAC name
Sodium dihydrogen phosphate
Other names
monobasic sodium phosphate;
sodium dihydrogen phosphate;
sodium biphosphate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.028.591
UNII
Properties
NaH2PO4
Molar mass 119.98 g/mol
Appearance White powder or crystals
Density 2.36 g/cm3 (anhydrous)
59.90 g/100 mL (0°C)
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored 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).
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Infobox references

Monosodium phosphate (MSP), also known as monobasic sodium phosphate and sodium dihydrogen phosphate, is an inorganic compound of sodium with a dihydrogen phosphate (H2PO4−) anion. One of many sodium phosphates, it is a common industrial chemical. The salt exists in an anhydrous form, 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

  1. 1 2 Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in Ullmann’s Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_465.pub3
  2. ↑ Salaun, F.: "Influence of mineral environment on the buffering capacity of casein micelles", "Milchwissenschaft", 62(1):3
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