Sodium sulfite
CAS 7757-83-7
EC 231-821-4
Formula H2O3S.2Na
MW 126.04 g/mol
Salts & Minerals Water TreatmentFood & NutritionTextile, Leather & PaperPharmaceuticals & Healthcare Preservation & BiocideAntioxidant & StabilizerCatalysispH Regulation & Buffering
Description
Sodium sulfite (CAS 7757-83-7) is an inorganic sodium salt registered as food additive E 221, also known by the abbreviations Na2SO3 and S-WAT. It functions as a reducing agent by donating electrons to oxidising species, making it effective as an antioxidant, preservative, and oxygen scavenger across multiple industrial sectors.
In water treatment, sodium sulfite removes dissolved oxygen from boiler feedwater by reacting directly with O2, preventing corrosion in steam systems. In textile processing, it acts as a reducing agent in dye baths and as a delignification aid in pulp bleaching. Food and pharmaceutical manufacturers use it to inhibit oxidative spoilage and microbial growth in aqueous formulations.
Sodium sulfite is available in food-grade (E 221, FCC), pharmaceutical-grade (Ph.Eur.), and technical-grade forms, supplied as anhydrous powder or granules. It is registered under REACH and compliant with EU food additive regulations. Standard packaging includes 25 kg bags and 1000 kg big bags.
In water treatment, sodium sulfite removes dissolved oxygen from boiler feedwater by reacting directly with O2, preventing corrosion in steam systems. In textile processing, it acts as a reducing agent in dye baths and as a delignification aid in pulp bleaching. Food and pharmaceutical manufacturers use it to inhibit oxidative spoilage and microbial growth in aqueous formulations.
Sodium sulfite is available in food-grade (E 221, FCC), pharmaceutical-grade (Ph.Eur.), and technical-grade forms, supplied as anhydrous powder or granules. It is registered under REACH and compliant with EU food additive regulations. Standard packaging includes 25 kg bags and 1000 kg big bags.
Physical Properties
| Melting Point | 500 °C |
| Density | 2.63 g/cm³ |
| Appearance | Sodium sulfite is a white crystalline solid |
| Color | White to slightly yellow |
| Odor | Odorless |
| Form | Solid |
| Water Solubility | 23 g/100 mL (20 ºC) |
| Refractive Index | 1,484 |
| pH | 9.0-10.5 (25℃, 1M in H2O) |
Safety & Handling (Learn More)
Danger GHS05 GHS07
H
H302H314H315H318H319
P
P260P264P270P280P316P317P321P330P363P405P501P264+P265P301+P317P302+P352P304+P340P332+P317P337+P317P362+P364P301+P330+P331P302+P361+P354P305+P351+P338P305+P354+P338
Trade & Regulatory
| HS Code | 28321000 |
| Storage Class | 13 - Non Combustible Solids |
| WGK (Germany) | 1 |
Other Names
Na2SO3sodium sulphitedried sodium sulfiteE 221S-WATnatriumsulfidnatriisulphisnatriumsulfit
Related Products
Raw Materials
Derivatives
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