Oxalic acid

Ball-and-stick model of oxalic acid. White balls are hydrogen, red balls are oxygen, and black balls are carbon. Each line shows one chemical bond.

Oxalic acid (also known as ethanedioic acid) is a chemical compound made of carbon, hydrogen, and oxygen. Its chemical formula can be written as H
2C
2O
4 or (COOH)
2. It is the simplest dicarboxylic acid, a type of chemical which has two COOH functional groups. A salt of oxalic acid is called an oxalate.

Oxalic acid is found in many plants. It is named for the genus Oxalis, also known as wood sorrels, where it was first discovered in the 18th century.

Oxalic acid is a weak acid according to the chemical definition, meaning it does not completely separate into hydronium ions and oxalate when mixed with water, but it is one of the strongest carboxylic acids, with a pKa of 1.2. Stronger organic acids usually contain other elements like nitrogen, sulfur, or fluorine.

Oxalic Acid Media

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  Stems of Oxalis triangularis contain oxalic acid.

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  Honeybee coated with oxalate crystals