Potassium Metabisulfite is a common additive used to preserve and stabilize wines, ciders, and occasionally beers. When added to wine or must, it forms sulfur dioxide gas (SO2). This prevents most wild microorganisms from growing and acts as a potent antioxidant, protecting both the color and delicate flavors of wine. As a sanitizer - use 2 oz per 1 gallon of water. As an antioxidant and bactericide - use 1/4 teaspoon to 6 gallons. Dissolve sulphite in warm water before adding.