Sodium bisulfite

Sodium bisulfite (CAS 7631-90-5), also sold as sodium bisulphite and designated E222 in food applications, is an inorganic sulfite salt used commercially as a reducing agent, preservative, and oxygen scavenger.

Where is Sodium bisulfite used?

• Food and beverage: E222 prevents oxidative browning and microbial spoilage in fruit products, wines, dried foods, and seafood processing
• Water treatment: dechlorination of potable water
• Boiler feedwater: neutralizing residual chlorine before downstream processing or discharge
• Textile and paper: bleaching and reducing agent for pulp brightening and dye stripping
• In pharmaceutical manufacturing it functions as an antioxidant stabilizer in injectable formulations and oral liquid preparations.
• Photography: used as a reducing agent in development and fixing.
• Textile dyeing: used in reduction dyeing, for example indigo for jeans.
• Oil and gas: used for oxygen removal in pipeline and drilling systems.
• Latex and rubber production: used as a stabilizer and reducing agent.
• Chemical industry: used in the synthesis of various compounds and as a reducing agent in certain reactions.

Formulation notes

• Weak acid; attacks metals.
• Solution is corrosive to aluminum.

Typical specification

• Available as a 38–40% aqueous solution.

Regulatory status

• Aqueous solution is assigned UN number 2693 for transport.
• Aqueous solution has hazard label class 8 (corrosive).
• Occupational exposure limit is TLV 5 mg/m³ as TWA, with A4 classification (not classifiable as a human carcinogen).
• Harmonized-classified under EU Regulation 1272/2008 (CLP) with hazard statement H302.

Storage, packaging and handling

• Reacts with acids and strong oxidants, creating a fire hazard.
• Must be stored separately from acids, strong oxidants, and food and feedstuffs, in well-closed containers.
• IBC packing instruction IBC03 applies to aqueous solution.

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