Potassium metabisulphite (K₂S₂O₅), also known as potassium pyrosulfite or potassium disulfite, is a white crystalline powder with a pungent odor of sulfur dioxide. It is a potassium salt of sulfurous acid.
Here's a breakdown of its key aspects:
Properties:
- Appearance: White crystalline powder or granules.
- Odor: Sharp, pungent odor of sulfur dioxide.
- Solubility: Freely soluble in water, insoluble in alcohol.
- Decomposition: Decomposes at around 150-190 °C, releasing sulfur dioxide gas.
- Antioxidant and Preservative: It acts as a reducing agent and releases sulfur dioxide (SO₂) in acidic solutions, which has antimicrobial and antioxidant properties.
Uses:
Potassium metabisulphite has a wide range of applications, primarily due to its ability to release sulfur dioxide:
- Food and Beverage Industry:
- Preservative: Inhibits the growth of bacteria, yeasts, and molds, extending the shelf life of various foods and beverages. It is commonly used in fruit juices, dried fruits, pickles, canned goods, and baked goods.
- Antioxidant: Prevents browning and discoloration in fruits and vegetables.
- Winemaking: Used for sterilizing equipment, inhibiting wild yeasts and bacteria, preventing oxidation, and stabilizing the wine.
- Brewing: Inhibits the growth of wild bacteria and fungi and neutralizes monochloramine in tap water.
- Water Treatment: Used to dechlorinate water. It reacts with chlorine and chloramine to neutralize them.
- Textile Industry: Used as a bleaching agent for textiles like wool and cotton.
- Photography: A component in some photographic developers and processing solutions.
- Gold Mining: Sometimes used to precipitate gold from solutions.
- Laboratory Reagent: Used in various chemical analyses.
- Pharmaceutical Industry: Used as an antioxidant and preservative in some pharmaceutical formulations.
