Sodium dithionite

Sodium dithionite (CAS 7775-14-6), also sold as sodium hydrosulfite, is a powerful reducing agent used industrially for bleaching, stripping color, and preventing oxidation.

Where is Sodium dithionite used?

• Textile manufacturing: primary reducing agent for vat dye application
• It reduces insoluble dyes to their soluble leuco form so they can penetrate fiber, then re-oxidize to fix color
• Pulp and paper: brightens mechanical pulp without chlorine-associated fiber degradation
• Food processing: antioxidant and preservative protecting dried fruits, starches, and wine from discoloration and oxidative spoilage
• Water treatment: dechlorination and oxygen removal in boiler feed systems and reverse osmosis pretreatment
• Reduces ketone, aldehyde, nitro, nitroso, quinone, alkyl halide and azo groups.
• Removes iron stains in water treatment.
• Additive in kraft pulping to improve yield.
• Chemical reactant and oxygen scavenger in synthetic rubber production.

Formulation notes

• Decomposes on contact with acids, producing toxic gases.
• For kraft cooking additive, the most promising conditions are pH 12.5, 0.4 M concentration, at 100 °C.

Typical specification

• Supplied at 85-87% assay.
• Maximum iron content is 0.01%.
• Maximum heavy metals content is 0.002%.
• Offered in purified grade.

Regulatory status

• Classified under RIDADR UN 1384 4.2/PG 2.
• Has EU CLP index number 016-028-00-1.
• Has WGK Germany 1 classification.

Storage, packaging and handling

• Should be stored dry, well closed, separated from strong oxidants and acids, in an area without drains or sewer access.

Frequently asked questions about Sodium dithionite

In which synthesis is sodium dithionite used as a reactant?

It is used in the synthesis of pyrithione.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.