J^^luoric Acid of Gay Lussac. 355 



An ebullition was soon heard in the alembic, and occa- 

 sionally there was a puff of dense fluoric acid vapor, from 

 the mouth of the receiver, which, to avoid explosion, was 

 allowed to remain a little loose around the tube. We did 

 not measure the acid which we obtained, but judged that it 

 was about one ounce in quantity. 



The fumes that occasionally broke out from the appara- 

 tus, instantly and powerfully corroded some articles of glass 

 that were near by, and the contact of them with the skin 

 or lungs, was most anxiously avoided. For this purpose, 

 the hands were covered with very thick gloves, and the 

 acid was never poured from the bottle, except under the 

 flue. 



Whenever the bottle was opened, a dense cloud of 

 white vapor appeared, and when a drop of the acid was al- 

 lowed to fall into water, it produced much the same com- 

 motion and noise as red hot iron; exciting great heat and 

 ebullition. A few drops placed in a small concave copper 

 dish, instantly inflamed potassium, which burnt with a 

 bright light, and was immediately dissipated. 



A drop of the acid, let fall into a dry wine-glass, or upon 

 a dry glass plate, promptly corroded and dissolved the 

 surface, with as much energy as that with which sulphuric 

 acid acts on potash. 



For the purpose of procuring an acid adapted to the 

 purpose of etching on glass, the experiment was repeated, 

 with this difference, that half an ounce of water was placed 

 in the receiver. This acid however, proved too powerful 

 for this purpose, as it corroded and destroyed the varnish* 

 used to protect the glass. When it was diluted with three 

 or four parts of water, it acted in the happiest .manner. 

 Plates of glass being properly prepared, with the compo- 

 sition of bees' wax and turpentine, and surrounded at the 

 edge by a rim of the same substance, were perfectly etched in 

 the course of a minute or two. The progress of the corrosion 

 in the parts denuded by the graver, could be distinctlyseen. 

 The same portion of acid, by pouring it from one plate to 

 another, served to etch several in succession; and indeed with 



*The common engravers^ varnish is very apt to be destroyed, even by a 

 very vveakacid; but we found that the varnish or mastick recommended by 

 Gay Lussac and Thenard, made by melting together common turpentine 

 and bees' wax, formed a perfect protection while the acid was of proper 

 strength. 



