Sodium thiosulfate

Sodium thiosulfate (CAS 7772-98-7), also sold as sodium thiosulphate and approved as E539, is an inorganic salt used industrially as a reducing and dechlorinating agent.

It neutralizes excess oxidants in process streams and protects sensitive materials from chlorine damage across multiple manufacturing sectors. In water treatment, it dechlorinates municipal and industrial effluent.

This is a standard step where residual chlorine would interfere with biological treatment. Textile and paper manufacturers use it to neutralize chlorine bleach after whitening operations, preventing fiber or pulp degradation.

In pharmaceutical manufacturing, it functions as an antioxidant stabilizer in injectable formulations and as an active ingredient in antidote preparations for cyanide and heavy metal exposure.

Photographic and printing workflows historically relied on it as a fixing agent to clear unexposed silver halides, a use still relevant in specialty analog processes for high-quality imaging.

Sodium thiosulfate is supplied as pentahydrate crystals, the most common commercial form, and as anhydrous powder where lower moisture content is required for specific chemical reactions.

Standard grades include USP, BP, and Ph. Eur. for pharmaceutical applications, alongside technical and food-grade specifications for industrial and food-contact uses.

Bulk quantities are available in bags and intermediate bulk containers to meet the logistical needs of large-scale manufacturing facilities and chemical processing plants worldwide.