Oxalic Acid naturally occurs in vegetables & plants like rhubarb & buckwheat. The powder is mixed with water turning it into oxalic acid. There are many uses at moderate levels, manufacturers use it for refinishing by lightning heavily stained wood furniture. Other Oxalic Acid Uses: Rust Removal- kitchen countertops, tubs, metal rust stains and plumbing pipes. Bleaching - Oxalic acid is used as a bleaching agent for both stone & wood surfaces. Stain lifter/ Remover-removes ink removes stains from fabrics, stone, brick, linoleum, wood, and vinyl. Cleaning agent- It is incorporated as an ingredient in many cleaning compounds Grinding agent for marble polishing Reducing agent in developing photographic film Wastewater treatment Calcium removal from wastewater It can be corrosive and toxic use protective gear when mixing and mix in a well-ventilated area, high doses are dangerous contact a doctor if there is an intake or reaction.