Sodium Hydrosulphite

Sodium Hydrosulphite (better known as Sodium dithionite) is a white crystalline powder with a weak sulfurous odor. It is produced by various processes (conversion of sodium formate or sodiumborohydride with sulphur dioxide, reduction of sulphur dioxide with zinc powder or reduction of sodium sulphide with Sodium amalgam.


Molar Weight174.107 g/mol
Melting Point52°C
Boiling Pointdecomposes
Flash Point100°C
Density2.38 g/cm³
FormsPowder, White, Crystalline

Uses and Applications

Key applications

  • Water treatment
  • Reducing agent
  • Decoloring agent
  • Bleaching agent


  • Pharma
  • Cleaning
  • Chemical Processing
  • Food

Synonyms: Sodium dithionite, Hydrosulfite, disodium dithionite

Chemical Formula: Na2S2O4

CAS Number: 7775-14-6