Benzoic Acid

Benzoic acid is a derivative of benzene with the chemical formula C₆H₅COOH. It consists of a carboxyl group attached to a phenyl group, and is thus the simplest aromatic carboxylic acid. It is also known as carboxybenzene, benzene carboxylic acid, and phenylformic acid.

In its pure form, benzoic acid exists as white needles or scales with a strong characteristic odor. It melts at 252.3°F (122.4°C), although it may also sublime at temperatures around 212°F (100°C). It dissolves only sparingly in cold water [0.4 g/100 g at 77°F (25°C)], but more completely in hot water [6.8 g/100 g at 203°F (95°C)].

Benzoic acid occurs naturally in gum benzoin, also known as benzoin resin or Benjamin gum, a brown resin found in the benzoin tree of Southeast Asia. It is also found naturally in many kinds of berries, where its concentration may reach 0.05%.

One of the most common uses of benzoic acid is as a food preservative. Both the acid and its sodium salt, sodium benzoate (usually listed on labels as benzoate of soda), are used to preserve many different kinds of foods, including fruit juices, soft drinks, pickles, and salad dressings. In fact, it is the acid rather than the sodium salt that is toxic to bacteria. Thus, the two additives can be used only in acidic solutions, where the sodium salt is converted to the acid form.

The acid and the sodium salt are both considered to be safe for human consumption in limited amounts. In the United States, foods may contain a maximum of 0.1% benzoic acid or sodium benzoate, although the limit in other nations may be as high as 1.25% in some types of prepared foods. Benzoic acid is also used in the manufacture of artificial flavors and perfumes and for the flavoring of tobacco.