35 Pa. Stat. § 932
The word "caustic" shall, within the intent and purpose of this act, be construed to mean any acids or alkalies in liquid or powdered form, or preparations thereof, on containing free or chemically unneutralized hydrochloric acid in a concentration of ten (10) per centum, or sulphuric acid in a concentration of ten (10) per centum, or nitric acid in a concentration of five (5) per centum, or carbolic acid (phenol) in a concentration of five (5) per centum or oxalic acid in a concentration of ten (10) per centum, or acetic acid in a concentration of twenty (20) per centum, or hypochlorous acid (calx chlorinata, bleaching powder, or chloride of lime) in a concentration of one hundred per centum (100), or potassium hydrate (caustic potash, Vienna paste, pearlash, potassa carbonas) in a concentration of ten (10) per centum, or sodium hydrate (caustic soda, concentrated lye) in a concentration of twenty (20) per centum, or silver nitrate (lunar caustic) in a concentration of five (5) per centum.
35 P.S. § 932