Overview
Potassium metabisulfite (CAS 16731-55-8 ), also sold as potassium pyrosulfite and approved as E224 , is an inorganic sulfite salt used industrially as a preservative, antioxidant, and reducing agent.
It releases sulfur dioxide upon contact with moisture or acids, making it effective for microbial control and oxidation prevention across food, beverage, and industrial applications.
In winemaking and brewing, it is the standard choice for sanitizing equipment, inhibiting wild yeast, and protecting finished products from oxidative spoilage during storage.
Food manufacturers use it to prevent enzymatic browning in dried fruits, potato products, and seafood processing. Water treatment operations rely on it to dechlorinate potable water.
It is also used for process streams before discharge or further treatment. In textile and leather processing, it functions as a bleaching and reducing agent during fabric preparation.
Potassium metabisulfite is supplied as a white crystalline powder or fine granules. Standard commercial grades include food-grade ( FCC ), pharmaceutical-grade ( USP , BP ), and technical-grade.
Purity levels typically range from 97% to 99%, with food and pharma grades carrying tighter sulfur dioxide content specifications to ensure safety and compliance for global distribution.
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Physical Properties
| Melting Point | 150 °C (decomp) |
| Density | 2.3 g/cm³ |
| Appearance | White to slightly yellowish fine cryst. powder |
| Color | White to slightly yellow |
| Odor | Odorless |
| Form | Powder/Solid |
| Water Solubility | Soluble in water. Insoluble in ethanol. |
| pH | 2.5-4.5 (25℃, 0.1M in H2O) |
Safety & Handling
Danger GHS05 GHS07 Hazard Statements H302 Harmful if swallowed H315 Causes skin irritation H318 Causes serious eye damage H335 May cause respiratory irritation Precautionary Statements P261 Avoid breathing dust/fume/gas/mist/vapours/spray. P264 Wash … thoroughly after handling. P270 Do not eat, drink or smoke when using this product. P271 Use only outdoors or in a well-ventilated area. P280 Wear protective gloves/protective clothing/eye protection/face protection. P317 Get emergency medical help. P319 Get medical advice/attention if you feel unwell. P321 Specific treatment (see … on this label). P330 Rinse mouth. P405 Store locked up. P501 Dispose of contents/container in accordance with local regulations. P264+P265 Wash … thoroughly after handling. P301+P317 Get emergency medical help. P302+P352 IF ON SKIN: Wash with plenty of water. P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing. P332+P317 Get emergency medical help. P362+P364 Take off contaminated clothing and wash it before reuse. P403+P233 Store in a well-ventilated place. Keep container tightly closed. P305+P354+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
Trade & Regulatory
| HS Code | 28322000 |
| Storage Class | 11 - Combustible Solids |
| WGK (Germany) | 1 |
Other Names
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Chemical Properties
- CAS Number
- 16731-55-8
- EC Number
- 240-795-3
- Mol. Weight
- 222.33
- HS Code
- 28322000
- Category
- Oxidizers & Peroxides