Sodium Metabisulfite
Sodium Disulfite
- CAS
- 7681-57-4
- EC
- 231-673-0
- Food Code
- E223
- Sectors
- Food & Nutrition, Water & Wastewater Treatment, Textiles, Leather & Paper
Sodium Metabisulfite (CAS 7681-57-4) is an inorganic sulfite salt supplied as a white to slightly yellow crystalline powder that releases sulfur dioxide and acts as a strong reducing agent, serving as an antioxidant and preservative in food, drugs and wine and as a bleaching agent in textiles and pulp. It has a density of 1.48 g/cm³, decomposes above 150°C, and is highly soluble in water (up to 650 g/L at 20°C), releasing sulfur dioxide. With a pungent SO2 odor, it acts as a strong reducing agent and is produced by reacting sodium bisulfite with sulfur dioxide.
Typical Properties
| Molecular formula | H2O5S2.2Na |
|---|---|
| Molecular weight | 294.17 g/mol |
| Form | Powder/Solid |
| Color | White to slightly yellow |
| Odor | Sulphorous |
| Melting point | 150 °C (decomp) |
| Density | 1.4 g/cm³ |
| Water solubility | 540 g/L (20 °C) |
| pH | 3.5-5 (50g/l, H2O, 20°C) |
| GHS signal word | Danger · Corrosive, Irritant / harmful, Health hazard |
| HS code | 28323010 |
| Grades available | Food Grade |
Typical literature values for identification; lot-specific results are stated on the certificate of analysis (COA) and the safety data sheet (SDS) that accompany every delivery.
Sodium Metabisulfite
Applications
Used as an antioxidant and preservative in food, drugs, and wine; antimicrobial in water treatment; bleaching agent in textiles and pulp, and in chemical synthesis.
Safety & Risks
Corrosive; releases toxic SO2 gas with acids, causing irritation to eyes, skin, and respiratory system; avoid inhalation and acids. Hazard Class 8 with proper ventilation.
Packaging
In 25kg bags or drums with inner liners for moisture protection; rinse containers for recycling or puncture for sanitary landfill disposal.