Sodium metabisulfite is an inorganic compound composed of sodium, sulfur and oxygen. Its chemical formula is Na2S2O5 . It typically comes in a white, or yellowish-white crystalline powder. It easily dissolves in water, which leaves that familiar sulfur (rotten egg) smell. Sodium Metabisulfite 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. However, those with allergies to sulfites — often exhibited by rashes, hives and wheezing – might try to steer clear of this preservative altogether. Main uses: Bleach agent (e.g.candies, cake, bamboo shoots, etc);Loose agent (e.g.bread, cracker etc);Antiseptic and germicide (e.g.fruit juice, tinned food ,brews, the cereals food is defended storage etc);Inhibitor and freshen agent (e.g.day lily, seafood, fruit and vegetable etc)