CAS #: 7647-01-0, Hydrochloric acid (HCl) is a clear, colourless, fuming and corrosive liquid that has a strong pungent odour. It is the aqueous solution of hydrogen chloride gas and a strong inorganic acid used in almost all sectors of different industries. Hydrochloric acid is used in the chemical industry as a chemical reagent in the large-scale production of vinyl chloride for PVC plastic, and MDI and TDI for polyurethane. It has numerous smaller-scale applications, including household cleaning, production of gelatin and other food additives, descaling, and leather processing.