Oxalic acid is an organic compound with the formula C₂H₂O₄. It is a colorless crystalline solid that forms a colorless solution in water. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C ₂O²⁻
₄), is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula C₂H₂O₄·2H₂O