Sodium phosphate, monobasic

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White, crystalline powder. Monobasic sodium phosphate, or MSP, is primarily used in baking powder. It also has applications in textile dyeing, electroplating and as a cleaner and emulsifier. In conservation, MSP has been used as a pH buffer in some enzyme-based cleaning gel mixtures (Chapman 1986).

Synonyms and Related Terms

MSP; sodium acid phosphate; sodium biphosphate; sodium orthophosphate; sodium dihydrogen phosphate; monosodium dihydrogen phosphate


  • May be harmful by ingestion.
  • Contact may cause irritation.

Physical and Chemical Properties

Soluble in water forming sodium metaphosphate at 350-400 C. pH =4.4 - 4.5 for a 1% solution. Insoluble in ethanol.

Composition NaH2PO4 - H2O
CAS 7558-80-7
Density 2.040 g/ml
Molecular Weight mol. wt. = 119.98
Refractive Index 1.4401, 1.4629, 1.4815

Resources and Citations

  • V. Chapman, "Amylase in a viscous medium: textile applications", The Conservator, no. 10 1986, pp. 7-11.
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8806
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: ref. index = 1.4401, 1.4629, 1.4815