Oxalic acid's main applications includes cleaning or bleaching, particularly for the removal of rust from metal. Its usefulness as a rust remover is due to its forming a stable, water-soluble ferric iron saline. Oxalic acid is also used as a bleach for wood and can easily remove black stains caused by dissolved iron that bonds with the wood. Beekeepers use it to keep mites off bees. Stone masons use it to polish marble and other stones. Oxalic acid has hundreds of different uses!