In the Know: Oxalic acid

Oxalic acid, also known as ethanedioic acid, is a colorless crystalline widely used as a bleaching or cleaning agent. It is a toxic organic compound with the formula C2H2O4 and may be present in some antirust products, bleaches, metal cleaners and rhubarb leaves.

The symptoms of oxalic acid poisoning include abdominal pains, burns and blisters, convulsions, kidney problems and shock. —Inquirer Research

Sources: www.britannica.com, www.nlm.nih.gov