Sodium metabisulfite
Specifications
Chemical formula: Na2S2O5
Molecular weight: 190.13
Appearance: white to yellowish powder
20% solution: colorless and transparent or yellowish
Packaging: in 25 kg, double-layer polyethylene bags or 1 mt jumbo bags
Chemical analysis
| Technical grade | Food/Photographic grade* | |
|---|---|---|
| Purity (Min.) | 97%±0.5% | 97%±0.5% |
| SO2 percentage (Min.) | 65.4% | 65.4% |
| PH (solution 50 g/liter) | 4.0 - 4.8 | 4.0 - 4.8 |
| Sodium thiosulfate (Max.) | ---- | 0.04% |
| Iron (Max.) | 0.002% | 0.001% |
| Heavy metals (as Pb) (Max.) | ---- | 0.001% |
| Arsenic (Max.) | ---- | 0.0002% |
| Zinc (Max.) | ---- | 0.0005% |
| Selenium (Max.) | ---- | 0.0005% |
| Sodium chloride (Max.) | ---- | 0.005% |
| Insoluble matter (Max.) | ---- | 0.015% |
| Ammonia silver nitrate test | ---- | Passed |
* This product complies with Iran’s food sodium metabisulfite standard (No. 3377) and the American food standard (Chemical Food Codex) E233 and the photographic type sodium metabisulfite standard (ANSI PH 4.276).
Applications
Sodium metabisulfite acts as a reductant, a bleach, and a preservative .
- In food and brewing industries, it is used as a preservative and anti fermentative, for dried fruits, sea foods, juice, etc.
- The photography industry uses sodium metabisulfite to prepare developer solutions and to acidify fixing baths.
- In tanneries, tannin extract is solubilized by it.
- Sodium metabisulfite is used to detoxify solutions containing chromic acid in electroplating shops and tanneries and to remove excess chlorine after destruction of cyanide.
- The paper and pulp industry use it to bleach groundwood.
- In chemicals manufacturing, sodium metabisulfite is a reducing agent for purifying and isolating aldehydes and ketones,for production of sulfosuccinates (base of baby shampoo), and for preparing dyes.
- In the Textile industry, it can be used to clean and bleach jute, wool, and other vegetable fibers, for preparing indigo vat dyes, as an antichlor after bleaching nylon, and as an activator in the polymerization of acrylonitrile.
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