Muriatic acid is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungent smell. It is effective for removing stains (including embedded oil stains) and mold from masonry and concrete (even in basements) with a solution of 1 cup of muriatic acid to 1 gallon of water. Removing stains and mold from tiled or concrete swimming pool surfaces. Removing rust from stainless steel.
