He called it "dephlogisticated muriatic acid air" since it is a gas (then called "airs") and it came from hydrochloric acid (then known as "muriatic acid"). He failed to establish chlorine as an element.

Common chemical theory at that time held that an acid is a compound that contains oxygen (the element's name is from the Greek roots ("acid") and ("producer", literally 'begetter'), so a number of chemists, including Claude Berthollet,