Oxalic acid is an organic compound with the formula H2C2O4. It is a colorless crystalline solid that dissolves in water to give colorless solutions. It is classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate, is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula H2C2O4·2H2O. Oral consumption of oxalic acid in excess or prolonged skin contact can be dangerous. Oxalic acid is mainly manufactured by the oxidation of carbohydrates or glucose using nitric acid or air in the presence of vanadium pentoxide. A variety of precursors can be used including glycolic acid and ethylene glycol. Anhydrous oxalic acid exists as two polymorphs; in one the hydrogen-bonding results in a chain-like structure whereas the hydrogen bonding pattern in the other form defines a sheet-like structure.
-V791.gif)