シュウ酸
Oxalic acid is an organic acid with the IUPAC name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early investigators isolated oxalic acid from flowering plants of the genus "Oxalis", commonly known as wood-sorrels. It occurs naturally in many foods, but excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.