Sodium phosphate, dibasic

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White, crystalline, hygroscopic powder. Dibasic sodium phosphate, or DSP, occurs in several hydrated forms from anhydrous to dodecahydrate. It is used in the manufacture of dyes, fertilizers, detergents, ceramics, and enamels. DSP is used as a Sequestrant, Emulsifier, and fire retardant. It acts as a Mordant in dyeing and is used for weighting Silk. DSP is also used as a replacement for Borax in soldering and brazing. In addition, DSP is used in bleach baths for color photographs.

Synonyms and Related Terms

DSP; disodium phosphate; secondary sodium orthophosphate; disodium hydrogen phosphate; phosphate of soda; Sorensen's phosphate (dihydrate)

Chemical structure

Sodium phosphate, dibasic.jpg


Physical and Chemical Properties

Soluble in water, ethanol.

Composition Na2HPO4 - xH2O
CAS 7558-79-4
Melting Point 240 C
Density 2.07 g/ml
Molecular Weight mol. wt. = 141.96
Refractive Index 1.4412, 1.4424, 1.4526

Resources and Citations

  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
  • Thomas C. Jester (ed.), Twentieth-Century Building Materials, McGraw-Hill Companies, Washington DC, 1995
  • 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 8805
  • 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 = 1.4412, 1.4424, 1.4526