﻿Mr. Gr. Gore on Hydrofluoric Acid. 471 



requires the most extreme degree of care in its manipulation. It is 

 a perfectly colourless and transparent liquid at 60° Fahr., very thin 

 and mobile, extremely volatile, and densely fuming in the air at or- 

 dinary temperatures, and absorbs water very greedily from the atmo- 

 sphere. It was perfectly retained in platinum bottles, the bottle 

 having a flanged mouth with a platinum plate secured with clamp- 

 screws, and a washer of paraffin. 



A number of attempts were made, finally with success, to deter- 

 mine the molecular volume of the pure anhydrous acid in the gaseous 

 state, the acid in these cases being prepared by heating pure anhy- 

 drous fluoride of silver with hydrogen in a suitable platinum apparatus 

 over mercury. Particulars are given of the apparatus employed and 

 of the manipulation. The results obtained show that one volume of 

 hydrogen, in uniting with fluorine, produces not simply one volume 

 of gaseous product as it does when uniting with oxygen, but two 

 volumes, as in the case of its union with chlorine. The gaseous 

 acid transferred to glass vessels over mercury did not corrode the 

 glass, or render it dim in the slightest degree during several weeks, 

 provided that moisture was entirely absent. 



The author concludes that the anhydrous acid he has obtained is 

 destitute of oxygen, not only from the various analyses and experi- 

 ments already referred to, but also, 1st, because the double fluoride 

 from which it was prepared, when fused and electrolyzed with pla- 

 tinum electrodes, evolved abundance of inflammable gas at the ca- 

 thode, but no gas at the anode, although oxides are by electrolysis 

 decomposed before fluorides ; 2nd, because the electrolysis of the 

 acid with platinum electrodes yielded no odour of ozone, whereas 

 the aqueous acid of various degrees of strength evolved that odour 

 strongly ; and, 3rd, because the properties of the acid obtained from 

 hydrogen and fluoride of silver agree with those of the acid ob- 

 tained from the double salt. He considers also that the acid obtained 

 from pure fluor-spar and monohydrated sulphuric acid heated to- 

 gether in a platinum retort is free from oxygen and water. 



The specific gravity of the anhydrous liquid acid was several times 

 determined, both in a specific-gravity bottle of platinum, and also by 

 means of a platinum float submerged and weighed in the acid. Con- 

 cordant and reliable results were obtained ; the specific gravity found 

 was 0*9879 at 55° Fahr., that of distilled water being= 1-000 at the 

 same temperature. 



The anhydrous acid was much more volatile than sulphuric ether. 

 Its boiling-point was carefully determined in a special apparatus of 

 platinum, and was found to be 67° Fahr. Not the slightest sign of 

 freezing occurred on cooling the acid to —30° Fahr. (= —34°- 5 C.) ; 

 and it is highly probable that its solidifying temperature is a very 

 great many degrees below this. Its vapour-tension at 60° Fahr. 

 was also approximately determined, and was found to be =7'58 lbs. 

 per square inch. On loosening the lid of a bottle of the acid at 

 60° Fahr., the acid vapour is expelled in a jet like steam from a 

 boiler ; this, together with the low boiling-point, the extremely dan- 

 gerous and corrosive nature of the acid, and its great affinity for 



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