18 ESSAY I. 



vitriolic expelled the fluor acid in the form of vapour. The 

 same powder formed, by means of the blowpipe, a yellowish 

 glass, which, however, evaporated by degrees, leaving at the 

 end a small globule of fixed glass behind. 



(d) Lead was not dissolved ; but with its calx the acid 

 formed a sweet solution, from which the calx could be 

 precipitated by vitriolic or muriatic acid, as also by sal 

 ammoniac. After digesting a quantity of acid with calx 

 of lead, which, having been previously digested with the same 

 calx, of course held some of it already dissolved, a spon- 

 taneous precipitation took place. The vitriolic acid expelled 

 that of fluor from the precipitate, in the form of corrosive 

 vapours. It was easily brought into fusion by means of the 

 blowpipe, when the acid flew off, and the calx of lead was 

 reduced. Part, however, of the glass remained fixed in the 

 fire. 



(e) Copper was partly dissolved ; for the acid, after 

 digestion with this metal, grew bluish on the addition of 

 volatile alkali. The calx of copper was readily soluble. 

 This solution was gelatinous ; yielding, however, blue crystals, 

 partly of a cubic, partly of an oblong form, from which the 

 acid could not be separated but by heat. 



(/) Iron was attacked with violence. The vapours which 

 arose during the solution were inflammable. The solution 

 had a taste like vitriol of iron ; it congealed during the 

 evaporation, but was not reducible into crystals, forming 

 only a hard mass after all the liquid was evaporated. 

 Vitriolic acid expelled from this mass the fluor acid 

 under the form of vapours. The same effect was like- 

 wise produced by simple heat ; and in this case a red 

 ochre or calx of iron was left behind. The calx of iron 

 was likewise soluble in this acid ; the solution had a 

 taste like alum ; it could not be reduced to crystals ; upon 



