Oxalic acid is a chemical that can be used, like many acids, as a cleaner for various things. For example, as a rust remover, a cleaning agent, on wood work as a stain lifter, as a bleaching agent, and many more. At high doses Oxalic acid can be dangerous, but at moderate doses it is safe for various useful functions. Use caution. Oxalic Acid Powders is often used to polish stone floors in conjuction with eiher steel wool pads or diamond dics and floor buffing machines. . When oxalic acid is applied on an old and graying wood floor, it brings back the wood floor’s natural white color. As a result, this acid is often used when preparing to stain old wood floors. It is also used by furniture manufacturers to lighten heavily stained areas of wood furniture in preparation for refinishing.