Acetic acid (CH3COOH), also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. Pure water-free acetic acid is a colourless hygroscopic liquid (that is, it readily absorbs water) that freezes below 16.7 °C (62 °F) to a colourless crystalline solid. Acetic acid is corrosive, and its vapour is irritating to eyes and nose, although it is a weak acid based on its ability to dissociate in aqueous solutions.
Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical that is used in the production of polyethylene terephthalate mainly in soft drink bottles; cellulose acetate, mainly for photographic film; and polyvinyl acetate for wood glue, as well as many synthetic fibres and fabrics. In households diluted acetic acid is often used in descaling agents. In the food industry acetic acid is used under the food additive code E260 as an acidity regulator.
The global demand for acetic acid is around 6.5 million tonnes per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from petrochemical feedstocks or from biological sources.