Medically reviewed by Mary Choy, PharmD Oxalic acid, or oxalate, is a naturally occurring organic compound in plant foods like vegetables, fruits, grains, and nuts. Your body also produces small ...

Oxalic acid, or oxalate, is a compound in many plant foods. In large quantities, it can inhibit the absorption of some nutrients. Learn more.

A: Oxalic acid is a potent but toxic cleaner that removes rust and stains caused by iron, water and tannic acid. It's available in dry crystal form, to be dissolved in warm water for use.

To use oxalic acid, mix one-half cup of the powder in a gallon of warm water and mop it on the stain. Let it work for five to 10 minutes, keeping the stain wet, then scrub with a stiff-bristled ...

Make a solution of oxalic acid crystals (available in paint stores) to saturation in hot water in a plastic bucket; never use metal with oxalic acid. Apply it to the stains with a paintbrush.