Lactic acid, also known as milk acid, is a chemical compound that plays a role in several biochemical processes. It is a hydroxy carboxylic acid. It was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. It is a carboxylic acid, whose chemical formula C3H6O3 has its hydroxyl group adjacent to the carboxyl group, making it an alpha hydroxy acid (AHA). In solution, it can lose a proton from the acidic group, producing the lactate ion CH3CH(OH)COOâˆ’. It is miscible with water or ethanol, and is hygroscopic.