1 Acetic acid, CH3COOH, also known as ethanoic acid, is anorganic acidthat gives vinegar its sour taste and pungent smell. 2 It is a weak acid, in that it is only a partially dissociated acid in an aqueous solution. 3 Pure, water-free acetic acid (glacial acetic acid) is a colourless liquid that absorbs water from the environment (hygroscopy), and freezes at 16.5 °C (62 °F) to a colourless crystalline solid. 4 The pure acid and its concentrated solutions are dangerously corrosive.

5 Acetic acid is one of the simplest carboxylic acids.