Sodium Hydrosulfite

Sodium hydrosulfite or sodium dithionite (Na2S2O4) is a white powder with a very slight sulfur odor. Although stable under most conditions, it decomposes in hot water or an acidic solution.


Sodium hydrosulfite, also known as sodium dithionite (Na2S2O4), is a white, crystalline powder or a yellowish-white crystalline solid when commercially available. 


  • Appearance: Sodium hydrosulfite is typically found as a white or yellowish crystalline powder.
  • Solubility: It is soluble in water, and its solution is known as sodium dithionite solution.


  • Textile Industry: Sodium hydrosulfite is widely used as a reducing agent in the textile industry for vat dyeing and bleaching of fabrics.
  • Paper Industry: It is used in the pulp and paper industry to bleach wood pulp.
  • Food Industry: In some countries, sodium hydrosulfite is permitted for use as a food additive, mainly as a reducing agent.
  • Water Treatment: It is used in water treatment processes to remove excess chlorine and other oxidizing agents.
  • Chemical Industry: Sodium hydrosulfite finds applications in various chemical processes, including as a reducing agent in organic synthesis.

Reducing Agent:

  • Sodium hydrosulfite is known for its powerful reducing properties. It can donate electrons and is used to reduce other substances in chemical reactions, particularly those involving the removal of oxygen.

Safety Considerations:

  • Sodium hydrosulfite can release sulfur dioxide gas, which can be irritating to the respiratory system. Adequate ventilation is essential when handling it.
  • It is a skin and eye irritant, and contact with the skin or eyes should be avoided. Personal protective equipment, such as gloves and safety goggles, is recommended.


Sodium hydrosulfite is sensitive to air and moisture. It should be stored in a cool, dry place, away from oxidizing agents.

Data sheet

CAS Number
HS Code
Chemical Formula
Other names
Sodium dithionite
White powder
reducing agent
Storage conditions
Sodium dithionite is generally stored in perfectly airtight steel containers.
50kg drum

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