ON FLUOR 



SECTION XII. 



That this siliceous earth was formed during the processes 

 themselves, appears from several experiments. 



(a) I poured vitriolic acid upon powdered fluor in a 

 cylinder of brass, which was closed by an exact cover, after 

 having suspended over the mixture an iron nail and a bit of 

 charcoal. Two hours afterwards I opened the vessel, and 

 found the nail and charcoal unchanged. I now moistened 

 them, and suspended them as before. The cover was put on 

 again, and, being removed in two hours, I found the nail, as 

 well as the coal, covered with a white powder, which had all 

 the properties of siliceous earth. In this experiment I made 

 no use of glass vessels. The siliceous earth, therefore, 

 obtained in the experiments (Sees, v., VI.) was not the 

 earth of the glass dissolved by the acid of fluor, and 

 afterwards precipitated, as one might otherwise suspect, 

 from the internal surface of the glass being so much 

 corroded. 



(6) The artificial fluor (Sec. x.) was treated in the same 

 manner, by means of vitriolic acid, as the native (Sec. vi.), 

 and distilled water was poured into the receiver for the 

 condensation of the acid. As soon as the fumes reached the 

 surface of the water, a white crust of siliceous earth was 

 formed. When no more acid came over, I filtered the liquor 

 contained in the receiver, and found it to be fluor acid 

 diluted with water. By means of lime-water, I obtained 

 a precipitate, which, like the former, was an artificial fluor, 

 and its acid was extricated by the vitriolic, with the same 

 phenomena as in the former experiment. Upon repeating 

 this experiment five times in the same manner, I constantly 

 found the siliceous earth and the acid diminish considerably, 



