Sodium benzoate (E211), also called benzoate of soda, 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. It can also be found in cough syrups like Robitussin. [1] 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 imparts a whistling noise when compressed into a tube and ignited.

It is found naturally in cranberries, prunes, greengage plums, cinnamon, ripe cloves, and apples. Concentration as a preservative is limited by the FDA in the U. S. To 0.1% by weight though organically-grown cranberries and prunes can conceivably contain levels exceeding this limit. [citation needed] 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. Sodium benzoate is, however, allowed as an animal food additive at up to 0.1%, according to AFCO's official publication.