Acetic acid, systematically named ethanoic acid, is an acidic, colourless liquid and organic compound with the chemical formula CH3COOH (also written as CH3CO2H, C2H4O2, or HC2H3O2). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water. It has been used, as a component of vinegar, throughout history from at least the third century BC.Acetic acid glacial dried 99.8% AR is a high-purity, Analytical Reagent (AR) grade of acetic acid characterized by its extremely low water content, typically not exceeding 0.05%. Acetic acid glacial dried 99.8% AR (Analytical Reagent grade) is a high-purity, nearly water-free solvent and reagent. Because it is specifically “dried” (water content usually), its uses are focused on applications where even trace amounts of moisture can ruin a reaction or analysis.