Sodium benzoate (E211) has the chemical formula NaC6H5CO2. It is the sodium salt of benzoic acid and exists in this form when dissolved in water. It can be produced by reacting sodium hydroxide with benzoic acid.

Sodium benzoate is a preservative. It is bacteriostatic and fungistatic under acidic conditions. It is used most prevalently in acidic foods such as salad dressings (vinegar), carbonated drinks (carbonic acid), jams and fruit juices (citric acid), pickles (vinegar), and condiments. It is also found in alcohol-based mouthwash and silver polish.[citation needed] It can also be found in cough syrups like Robitussin. Sodium benzoate is declared on a product label as ’sodium benzoate’ or E211.

It is also used in fireworks as a fuel in whistle mix, a powder which emits a whistling noise when compressed into a tube and ignited.

Sodium benzoate is produced by the neutralization of benzoic acid with sodium hydroxide.[2] Benzoic acid is a natural preservative found in cranberries, prunes, greengage plums, cinnamon, ripe cloves, and apples.[citation needed] Though benzoic acid is a more effective preservative, sodium benzoate is more commonly used as a food additive because benzoic acid does not dissolve well in water.[2] Concentration as a preservative is limited by the FDA in the U.S. to 0.1% by weight. The International Programme on Chemical Safety found no adverse effects in humans at doses of 647–825 mg/kg of body weight per day.

Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice.[5] Sodium benzoate is, however, allowed as an animal food additive at up to 0.1%, according to AFCO’s official publication.

Source: http://www.wikipedia.com