Oxalic acid is a white, crystalline solid, a dicarboxylic acid (dibasic carboxylic acid) that is slightly soluble in water. It is also known by the systematic name ethanedioic acid and has the chemical formula (COOH)₂, or C₂H₂O₄.

 

Oxalic acid is very poisonous and occurs in certain plants such as sorrel and the leaf blades of rhubarb. It is a mild reducing agent and is used as a standard in volumetric analysis. It is also used for metal and textile cleaning, and in tanning. Molecular weight 90.0, relative density 1.653, melting point 101.5°C (214.7°F).

 

Oxalic acid poisoning

Oxalic acid is a powerful local irritant; when swallowed it produces a burning sensation in the mouth and throat, vomiting of blood, breathing difficulties, and circulatory collapse. Treatment is with calcium lactate or other calcium salts, lime water, or milk.