Sodium Metabisulphite is commonly used as a food preservative for dried foods, like potato chips, raisins and apples, as well as fruit concentrate juices. As a food product, the safe daily intake of sodium metabisulfite has been determined to be about .7 grams per kilogram of body weight.
Sodium metabisulfite exists in both food-grade and non-food-grade forms. The non-food-grade form is an industrial bleaching and reducing agent; it is also used to remove excess chlorine from drinking water and as a photographic developing and fixing bath agent.
Sodium metabisulfite is an antioxidant additive in injectable medicines and is also used as a reducing agent in pharmaceuticals. Some medical lotions may contain sodium metabisulfite; even in topical preparations, however, sodium metabisulfite may induce allergic or sensitive reactions.
It is also used as an oxygen scavenger to eliminate the dissolved oxygen in waste water and in pipes. Bisulfite is a reductive bleaching agent. It reduces carbonyl and alcohol groups, which function as colorants of the substances. It is used in bleaching mechanical paper pulp, cotton, wool and kaolin clay. Additional applications include as a preservative (antioxidant), a hair waving agent, and Ensiling agent. Bisulfites are used in industries concerned with leather processing, food and beverage processing, gas purification, water treatment to remove excess chlorine, textiles and pulp processing, and many others. It is used as a reducing agent in chemical manufacturing. It is an alternative to sulfur dioxide which is used in sterlization of equipment.