Sodium Metabisulfite CAS 7681-57-4
Sodium Metabisulfite (CAS 7681-57-4) is an inorganic sulfite, a white to pale yellow powder with a sulfur dioxide smell. In water or acid it releases sulfur dioxide to reduce, bleach and block oxidation. Food plants use it as a preservative and color keeper under E223 in wine, dried fruit and seafood. Water plants use it to remove free chlorine, and it also serves leather, textile, photography and mining. UATChem supplies grades in 25 or 50 kg bags and ton bags, with COA, TDS and SDS on request.
- CAS: 7681-57-4
- EC Number: 231-673-0
- Type: Inorganic sulfite reducing agent
- Appearance: White to pale yellow powder
- Main Use: Preservative, bleaching, dechlorination
- Available Grades: Food / industrial
- Packaging: 25 or 50 kg woven bag
- Bulk Pack: FIBC ton bag
- Documents: COA, TDS and SDS on request
- Storage: Sealed, dry, away from air and moisture
- Samples: Available on request
What Sodium Metabisulfite Is
Sodium Metabisulfite is the disodium salt of disulfurous acid, formula Na2S2O5, CAS 7681-57-4, sold as white to pale yellow crystals. It dissolves in water, releases sulfur dioxide on contact with acid or heat and slowly oxidizes in air. SO2 reduces oxidants, bleaches color and protects food from browning and oxidation. In water treatment the sulfite removes free chlorine, while food uses E223. UATChem supplies it, with SO2 and assay on COA, TDS.
Food, Water, Leather and Industrial Uses
- Food (E223). It preserves, keeps color and bleaches in wine, dried fruit, juice and seafood.
- Water treatment. It removes free chlorine and reduces chromium in wastewater.
- Leather, textile and photo. It serves leather tanning, textile bleaching and photo developing.
- Mining and chemical. It acts as a reducing agent in ore processing and chemical synthesis.
Typical Specifications
SO2 content, assay, iron and heavy metal data vary by grade and are reported on the COA and TDS, while handling is covered by the SDS. The table below identifies the material.
| Parameter | Typical Value |
|---|---|
| CAS / EC | 7681-57-4 / 231-673-0 |
| Synonyms | Sodium Pyrosulfite; SMBS; Disodium disulfite |
| Molecular Formula | Na₂S₂O₅ |
| Molecular Weight | 190.11 |
| Appearance | White to pale yellow crystals, sulfur dioxide smell |
| Solubility | Dissolves in water |
| Function | Reducing, bleaching, preservative, antioxidant |
| Grades | Food (E223) / industrial |
| Transport | Classification per SDS |
Packaging, Documents and Ordering
- Orders ship in 25 or 50 kg woven bags, and larger volumes in FIBC ton bags, matching the photos. Keep the powder sealed, dry and away from air and moisture.
- Every lot comes with a COA, TDS and SDS covering SO2 and assay data.
- Samples are available for evaluation. To quote, UATChem needs the grade, quantity, packing and destination port.
FAQ
Q: What is sodium metabisulfite used for?
A: It preserves food under E223, removes free chlorine in water treatment, and serves leather, textile and mining.
Q: Is sodium metabisulfite a food preservative?
A: Yes, it releases SO2 that preserves, bleaches and stops browning in wine, dried fruit and seafood, listed as E223.
Q: How is sodium metabisulfite packed?
A: UATChem supplies the powder in 25 or 50 kg woven bags and FIBC ton bags, sealed, dry and away from air, with COA, TDS and SDS.
Q: Does sodium metabisulfite remove chlorine?
A: Yes, the sulfite reduces free chlorine in water for dechlorination, with assay and lot data on COA and TDS.
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