Wikipedia; 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. 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 (C2O42?), is a chelating agent for metal cations. Used as a rust and stain remover, concentrated cleaner, and to make metal oxalates for pyrotechnic applications. Vaporized oxalic acid, or a 3.2% solution of oxalic acid in sugar syrup, is used by some beekeepers as a miticide against the parasitic varroa mite. Soluble in water, ethanol and diethyl ether.