Benzoic acid

• BPBenzoic Acid
• JPBenzoic Acid
• Ph. Eur.Benzoic Acid
• USP–NFBenzoic Acid

Acidum benzoicum; benzenecarboxylic acid; carboxybenzene; dracylic acid; phenylcarboxylic acid; phenylformic acid; E210

Benzenecarboxylic acid · [65-85-0]

UNII 8SKN0B0MIM · PubChem CID 243

C7H6O2 · 122.12

Antimicrobial preservative

Typical concentrations: — · Dosage forms: Liquid, Semi-solid

Used as an antimicrobial preservative in oral, topical and some parenteral preparations, and widely in foods. It is effective only in its undissociated form, so it is used in products with a pH below about 4.5. Typical concentrations: oral solutions 0.01–0.1%; oral syrups about 0.15%; topical and vaginal preparations 0.1–0.2%; injections about 0.17%. It has also been used as a tablet lubricant and, with salicylic acid, as a keratolytic and antifungal.

White, lustrous crystalline plates, needles or powder, odourless or with a faint characteristic odour (of benzaldehyde or benzoin).

Melting point

≈ 122 °C; sublimes readily above about 100 °C

Boiling point

≈ 249 °C

pKa

4.2 (25 °C)

pH

about 2.8 (saturated aqueous solution)

Solubility

slightly soluble in water (about 1 in 300 at 20 °C), soluble in boiling water; freely soluble in ethanol, ether and chloroform; soluble in fixed and volatile oils

Stable. Aqueous solutions may be sterilised by autoclaving or filtration; some benzoic acid is lost with steam because it is volatile. Store in a well-closed container in a cool, dry place.

Reacts with alkalis and heavy-metal salts. Its preservative activity is reduced by nonionic surfactants and quaternary ammonium compounds and by raising the pH; it may be adsorbed by kaolin and some plastics and rubbers.

Produced commercially by liquid-phase air oxidation of toluene over a cobalt catalyst, followed by purification by sublimation, distillation or recrystallisation. It occurs naturally in gum benzoin and in many fruits.

Rapidly absorbed and conjugated with glycine in the liver to hippuric acid, which is excreted in the urine. At the levels used it is of low toxicity, but it can cause non-immunological contact urticaria and may provoke intolerance reactions in people sensitive to aspirin; benzoates can displace bilirubin and increase jaundice in neonates. JECFA has set a group ADI of 0–5 mg/kg body weight for benzoic acid and its salts.

Observe normal precautions for the quantity handled. The dust irritates the eyes, skin and respiratory tract; use eye protection, gloves and a dust mask, and avoid heating in confined spaces because the vapour is irritant.

GRAS listed. Accepted as a food additive in Europe (E210). Included in the FDA Inactive Ingredient Database (intramuscular and intravenous injections, irrigation solutions, oral, rectal, topical and vaginal preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Potassium benzoate; sodium benzoate; benzyl alcohol; benzyl benzoate.

Because of its low water solubility, sodium benzoate is often used instead and converted in situ to benzoic acid by the acidic pH of the formulation. The preservative is much more active against yeasts and moulds than against bacteria.