Sodium sulfite

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White, crystalline powder. Sodium sulfite is primarily used as a reducing agent in photographic fixers and as a replacement for 'hypo' (Sodium thiosulfate). It is also used for bleaching Wool, Straw, and Silk. Sodium sulfite acts as an antichlor for the removal of Chlorine in bleached textiles and Paper, but it can leave a residual Sulfur odor. It is also used for silvering Glass and preserving food.

Synonyms and Related Terms

sodium sulphite; disodium salt of sulfurous acid; disodium sulfite

Chemical structure

Sodium sulfite.jpg


  • Emits toxic fumes when heated.
  • Inhalation of powder may cause asthmatic reactions.
  • ThermoFisher: SDS

Physical and Chemical Properties

  • Soluble in water, glycerol.
  • Solutions smell sulfurous.
  • Insoluble in ethanol.
Composition NaSO3
CAS 7757-83-7
Melting Point 600 C (dec)
Density 2.633 g/ml
Molecular Weight mol. wt. = 126.06
Refractive Index 1.565, 1.515

Resources and Citations

  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Book and Paper Group, Paper Conservation Catalog, AIC, 1984, 1989
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8831
  • Photographic chemical at
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: ref. index= 1.565, 1.515
  • 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 American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

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