Hydrofluoric Acid: Fluorspar and Sulphuric Acid in a Lead Retort

The acid that etches glass. Thorpe (1912): powdered fluorspar with about twice its weight of strong sulphuric acid, gently heated in a lead retort, gives off hydrogen fluoride; led over water in a lead receiver it makes hydrofluoric acid. It eats glass, so lead or copper vessels are used throughout. Hydrogen fluoride is a deadly poison and its burns go deep: full protection, outdoors, never alone. The picture: our own drawing.