Sodium benzoate (E211), also called benzoate of soda, has chemical formula NaC6H5CO2. It is the sodium salt of benzoic acid and exists in this form when dissolved in water.
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 Chinese food sauces (soy, mustard, and duck). It is also found in alcohol-based mouthwash and silver polish. Sodium benzoate is declared on a product label as 'sodium benzoate' or E211. The taste of sodium benzoate cannot be detected by around 25 percent of the population, but for those who can taste the chemical, it tends to be perceived as sweet, sour, salty, or sometimes bitter.