Sodium sulfite (SS) is a white, odourless, crystalline powder with a sulfurous taste that has reducing properties. The compound is soluble in water (30.7/100 g/g at 25 °C), glycerol and slightly soluble in alcohol.

Uses

Its therapeutic use is related to the veterinary domain (as an antioxidant and antiseptic), its use in the food field is related to its antioxidant and preservative properties, and in the cosmetic field due to its preservative properties. Sulfites destroy vitamin B1 (thiamine) in food, and their use is restricted to products that are major sources of vitamin B1. An acceptable daily intake (ADI) of sulfites (expressed as sulfur dioxide) was defined as 0.7 mg/kg body weight, and products (food, beverages) containing more than 10 mg/kg or 10 mg/L are subject to mandatory labelling (European Commission, 2011). Industry uses are related to the following properties: antioxidant, brightener, corrosion inhibitor, fixing agent, oxidizing agent, plasticizer, preservative, reducing agent, solvent, surface active agent, and pH regulating agent. Consumer uses are based on the following: fixing agents, oxidizing/reducing agents, paint and coating additives, photosensitive chemicals, preservatives, softeners, and conditioners. Processes on an industrial scale with risk of exposure are glass manufacturing, petroleum production and refining, photographic processing, textiles, and using disinfectants or biocides.

Safety

Exposure to sodium sulfite, especially powder, can cause irritation to the skin, eyes, and respiratory tract. If inhaled, sulfites may cause sensitization (develop an allergic reaction). Breathing sulfite dust may aggravate asthma or other pulmonary (breathing) diseases and cause headaches, breathing difficulties, or heart irregularity. Ingestion may cause gastrointestinal irritation, nausea, vomiting and diarrhea. Overexposure may result in death.