Water/20 cc This does not etch glass but removes a thin layer. It is especially good for removing silica, carbon, and metal films. As it is corrosive to the skin, it should be handled with care. Formula No.3 (Nonvolumetric Glass Hydrofluoric Acid/5 Nitric Acid/33 "Teepol" (Alkylaryl Sulfonate)/2 Water/60 b: Sulfuric Acid (Conc)/100 cc a: Sodium Dichromate/20 g Nitric Acid/33 Hydrofluoric Acid/5 Alkylaryl Sulfonate/2 Water/60