Oxalic acid is an important household chemical that can be used, like many acids, as a cleaner for various purposes; for example, as a rust remover, cleaning agent, a stain remover on wood, a bleaching agent, and more. This acid is a natural component of plants and vegetables such as buckwheat and rhubarb, and is available for purchase in powder form at your local home improvement depot. The oxalic powder is then mixed with water to form an oxalic acid solution. At high doses, oxalic acid is very dangerous, but in moderate doses, it is safe for various beneficial functions.