LABORATORY PREPARATION OF HYDROFLUORIC ACID ARNOLD BOOKHEIM Williamson Central School. Williamson, New York LACKING a supply of hydrofluoric acid in our stock room, we found it necessary, in order to etch glass, to make hydrogen fluoride from calcium fluoride and snlfuric acid in a lead dish. Several members* of our chemistry class, in working out a project, found they had a considerable amount of etching to do. They decided to make some hydrofluoric acid. The apparatus used (see diagram) consisted of a retort made of about two feet of 11/4'' I.D. lead pipe. A lead bending spring was placed in the pipe and it was bent to the proper curve. The spring was removed by beating the sides of the curved pipe with a wooden paddle. The surplus on the ends was trimmed off and the discharge end was brought down to a smaller size by beating with the same paddle. No lead-burning outfit was available, so the reaction end of the retort was closed by flattening one inch of the pipe in a vise and folding over one half of the flattened portion.
Powdered calcium fluoride was placed in the retort by means of a long paper cone, and concentrated sulfuric acid was poured in through a funnel and rubber tube. The discharge end of the retort was placed inside a paraffin-coated bottle containing distilled water, and the bottle was surrounded by snow in a pneumatic trough. The retort was then heated for forty minutes.
LABORATORY PREPARATION OP HYDROPLUORIC Acm
The liquid was tested by allowing a microscope slide to stand in i t overnight. The slide was half dissolved the next morning. The necessary etching was then done with this home-made hydrofluoric acid.
