VERY toxic, especially to the kidneys. It is great as an electrolyte in electrolytic rust removal baths, but watch contact, vapors, and solutions. I keep a supplycoaledsweat wrote: ↑Tue. Nov. 20, 2018 10:10 amPlease note: Oxalic is toxic to humans. Citric is not.
"theWorks" toilet bowl cleaner is concentrated HCL. Nasty vapors, try in hidden area first. Works GREAT on water iron/rust stains, which many are results from coal seams in well water. Should be very similar "type" of stains.