ON FLUOR ACID 31 



hitherto formed concerning the earthy matter which appears 

 on this occasion. 



SECTION V. 



Mr. Scheele's explanation of the phenomena appeared to 

 me, on the first reading of his Essay, somewhat bold and 

 improbable. For we are not acquainted with any instance 

 in which water is thus changed into an earth by an acid, 

 and still less with a transmutation of this liquid into siliceous 

 earth. I endeavoured, therefore, to discover its origin by 

 experiment. Having therefore first repeated several experi- 

 ments in the way described by Mr. Scheele, accurately 

 observed all the phenomena that occurred, and thus fallen 

 upon a track which promised to lead to the solution of the 

 whole problem, I proceeded to something which Mr. Scheele 

 had neglected, and from which I hoped that it might be 

 ultimately determined whether the earth proceeded from the 

 fluor, or was formed of the acid and water. 



SECTION VI. 



For this purpose I first weighed the retort destined for 

 the experiment in a very accurate manner, and found that its 

 weight was 2 oz. 5 drms. I then put into it 2 oz. of calcined 

 fluor in powder, and added, by means of a glass tube, 2J oz. 

 of oil of vitriol. The retort was then placed on the furnace, 

 and a receiver, which, when empty, weighed 2 oz. 2 drms. and 

 30 grs., and now contained 2 oz. of distilled water, luted to 

 it. The distillation was conducted with all possible care, 

 and at last pushed till the retort grew red hot. A few 

 vapours could not be prevented from penetrating through 

 the lute. The next day, the retort being separated from the 

 receiver, was found to weigh, together with its contents, 



