ON FLUOR ACID 37 



40 grs. of an ammoniacal salt in thin prismatic crystals ; but, 

 upon examining the cup, I found all the glazing corroded, 

 and the bottom as rough as a file. During the evaporation, 

 the cup was covered with white paper, which, when dry, 

 appeared full of small crystals of an acid taste, easily 

 distinguishable with the naked eye. These, as well as the 

 ammoniacal salt, forcibly attracted moisture from the air. 



SECTION XVI. 



From the properties of fluor acid, with which we are now 

 become acquainted, all Mr. Scheele's other observations may 

 be quite naturally explained : as, for instance, that regenerated 

 fluor still continues to yield siliceous earth when it is distilled 

 with vitriolic acid ; that fluor acid, by being merely rectified, 

 always leaves behind siliceous earth, and yet passes over still 

 loaded with that earth ; that the ammoniacal salt, in the 

 formation of which the siliceous earth is separated by volatile 

 alkali, yet yields an acid, when it is mixed with vitriolic 

 acid and distilled, that contains this earth. But the know- 

 ledge of so singular an acid may lead to much further in- 

 struction, as we are already certain that it completely and 

 abundantly dissolves flint, quartz, and glass, the only refractory 

 bodies. From this quality, it must also be apparent to every 

 one that the present can neither be the acid of salt nor of 

 vitriol, but one totally different from all before known, and 

 peculiar to fluor. 



At the same time, we must perceive the almost insuper- 

 able difficulty of obtaining it pure, and ascertaining its effects 

 on other bodies. 



