Oxalic acid is a colorless, crystalline organic compound with the formula C2H2O4. It is a dicarboxylic acid found in various plants, including rhubarb and spinach. In food, it can contribute a sour taste and is used in cleaning agents and as a bleaching agent. Oxalic acid plays a role in the metabolism of certain plants and can form insoluble salts with calcium, which is significant in dietary contexts. While it has applications in food processing, excessive consumption can lead to health issues due to its toxicity.