174 
ME. G. GOEE ON HYDEOELUOEIC ACID. 
and 1^ part of crystallized chloride of calcium, through the open tube B. A platinum 
bottle, C, immersed in a similar freezing-mixture, was employed to receive the distil- 
late. The bottle was provided with a three-necked angle-tube of platinum (see fig. 2), 
through the narrow opening, D, of which the condensing-tuhe passed into the bottle, 
and the angle-tube had a long exit-tube of platinum, F, fixed upon its larger open- 
ing, E. The exit-tube had upon its upper end a short angle-tube of platinum, G, turned 
downwards to prevent attracted moisture running down into the bottle (see fig. 3)*. 
The tubes all fitted tightly, and the cold junctions were made gas-tight by means of a 
mixture of melted paraffin and lampblack f. 
Heat was now gradually ap- p. 3 
plied and the acid rapidly dis- 
tilled until (in about twenty 
minutes) the bottom of the re- 
tort became red-hot, indicating 
a completion of the process. 
The materials bumped consi- 
derably towards the end of the 
process (this may be dimi- 
nished by applying the heat to 
the side of the retort), and a 
small quantity of the salt was 
carried mechanically over. The freezing-mixture is indispensable, and careful manage- 
ment of the heat is required. Care must be taken to have all parts of the apparatus 
quite free from moisture, and also from traces of fluoride of potassium, which is 
highly deliquescent, and is acted upon with dangerous violence by the acid. The acid 
was redistilled without exposing it to the air, the retort being immersed in a bath of 
slightly warm water, kept at a temperature not exceeding 100° Fahr. ; under these 
circumstances any traces of water contained by the acid was retained in the retort by 
the small quantity of saline matter. 2800 grains of the acid usually carried over 
mechanically about 5 or 10 grains of saline matter in the first distillation. 
The acid thus obtained is a highly dangerous substance, and requires the most extreme 
care in its manipulation J : it left no fixed residue on evaporation; it was a perfectly 
* All the platinum apparatus used in this investigation was constructed for me with great care by Messrs. 
Matthey and Co., and without such apparatus the experiments could not possibly have been made. 
t Paraffin answers admirably for resisting hydrofluoric acid where heat is not applied ; it may easily be 
formed into stoppers, cups, plates, rods, and almost any desired shape ; it is, however, liable to become full of 
cracks when suddenly immersed in a freezing-mixture. Temporary stoppers were conveniently made by melting 
paraffin in a test-tube, and then breaking the tube. 
+ The highly dangerous nature of the anhydrous acid has received further confirmation in the recent sudden 
death of Professor Nickles of Nancy, which, according to the ‘ Moniteur Beige’ of April 14th, 1869, was occa- 
sioned by accidentally inhaling the vapour of the concentrated acid whilst engaged in making experiments to 
isolate fluorine. 
