The first one is acetic acid, which is also called ethanoic acid. It is the second simplest carboxylic acid (after formic acid) and is a sour-tasting, foul-smelling liquid. Acetic acid is made up of a methyl group (CH₃-) bonded to a carboxylic acid group (-COOH), making it acidic. Glacial acetic acid is the pure form of acetic acid and gets its name because it crystallizes into ice-like solids at temperatures less than 16.6 °C (62 °F). It is miscible with water and a variety of organic solvents and is an important chemical intermediate.
Acetic acid occurs naturally in trace amounts in both plant and animal tissues and is involved in metabolic processes. Acetic acid, because it is a weak acid, only partially dissociates in water, which means it releases a moderate amount of protons compared to strong acids such as hydrochloric acid. Its multiplicity of properties makes it a common material in the food, pharmaceutical, chemical and agricultural industries.