acetic acid, CH₃CO₂H, colorless liquid that has a characteristic pungent odor, boils at 118°C;, and is miscible with water in all proportions; it is a weak organic carboxylic acid (see carboxyl group). Glacial acetic acid is concentrated, 99.5% pure acetic acid; it solidifies at about 17°C; to a crystalline mass resembling ice. Acetic acid is the major acid in vinegar; as such, it is widely used as a food preservative and condiment. For industrial use concentrated acetic acid is prepared from the oxidation of acetaldehyde. Acetic acid is also a product in the destructive distillation of wood. It reacts with other chemicals to form numerous compounds of commercial importance. These include cellulose acetate, used in making acetate rayon, nonflammable motion-picture film, lacquers, and plastics; various inorganic salts, e.g., lead, potassium, and copper acetates; and amyl, butyl, ethyl, methyl, and propyl acetates, which are used as solvents, chiefly in certain quick-drying lacquers and cements. Amyl acetate is sometimes called banana oil because it has a characteristic banana odor.

Most important carboxylic acid (CH₃COOH). Pure (“glacial”) acetic acid is a clear, syrupy, corrosive liquid that mixes readily with water. Vinegar is its dilute solution, from fermentation and oxidation (see oxidation-reduction) of natural products. Its salts and esters are acetates. It occurs naturally as a metabolic intermediate in body fluids and plant juices. Industrial production is either synthetic, from acetylene, or biological, from ethanol. Industrial chemicals made from it are used in printing and as plastics, photographic films, textiles, and solvents.

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