question about oxalic acid and stain removal
Bill Tindall, E.Tn.
I have never used it, so no hands- on experience.
Most chemicals that combine with iron make colored compounds. For example, the lignin in wood combines with iron ions from a corroded clamp surface and makes a blue colored iron compound that looks black when it is concentrated enough.
Oxalic acid and citric acid are the exceptions. They like to combine with iron and the result is a colorless compound. Oxalic acid will suck the iron out of the black lignin compound and make a water soluble colorless iron compound. Oxalic acid is, or at least was, an ingredient in commercial iron stain removal products for this reason.
Unlike chlorine bleach, oxalic acid does not de-color by destroying the chemicals that are making color, for example mold colors. The question: does oxalic acid remove stains other than iron? Might one need to know the kind of stain before attacking it with this or that chemical?
Oxalic acid is a two part chemical- and acid and oxalate. The acid part is an irritant. The acid part will be neutralized by any base- baking soda, borax, lye, etc. The oxalate part is a poison. Adding a base such as bicarbonate does not diminish the toxicity of the oxalate. What dose of oxalic acid causes harm is a topic too complex to be settled here. Look up the MSDS for oxalic acid and draw your own conclusions.
