Sodium Metabisulfite is the main constituent of commercial dry Sodium Bisulfite, whose uses and properties are virtually identical. Aqueous solutions of Sodium Metabisulfite have a strongly acidic reaction.
When mixed, it gradually releases gaseous sulfur dioxide, during which an oxidation to Sodium Sulfate occurs. In acidic and hot environments, Sodium Metabisulfite releases sulfur dioxide. Sodium Metabisulfite reacts violently with oxidizing agents. It has reducing, bleaching, and preservative properties.
Sodium Metabisulfite is used in the food, chemical, and pharmaceutical industries. In the food industry, it is used as a food additive, with its most important applications including the treatment of: dried, syruped, and candied fruits; fruits and vegetables; onions and potatoes; dry starch, barley, edible gelatin; hard and soft candies; preservation of jellies and jams; fermentation of vinegar, citrus fruits, grapefruit juice, and orange juice; fish, shrimp, and other shellfish; in the production of certain types of wheat flour (pasta); and for bleaching pineapple and processing coffee beans.
It is used in drinking water treatment to neutralize excess chlorine and, in special cases, to remove oxygen and purify wastewater containing chromium. In the adhesives, arts, tanning, cleaning and maintenance, photographic, pulp, and paper industries, it is used as a reducing agent in the polymerization of synthetic fibers. In the textile industry, it is used for fabric bleaching, as an antichlor agent, and as a reducing agent in dyeing and printing processes.
