Monosodium phosphate

(Redirected from Monobasic sodium phosphate)

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 (H2PO4). 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]

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 Edit this at Wikidata
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 diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
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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Production and reactions

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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

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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

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

Detection of magnesium

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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

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  1. ^ a b 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.