30 ESSAY III. 



portion of the acid is condensed, and forms with the water 

 an acid liquor. 



SECTION III. 



Having, moreover, observed that the liquor separated by 

 nitration from the earthy crust, coagulated on the addition 

 of alkaline salts, and, when it was more diluted, yielded a 

 semitransparent, gelatinous, and viscid precipitate, he con- 

 sidered the coagulation as a property of the acid itself, not 

 imagining that there took place a separation of any earthy 

 substance that was combined with the proper acid. He 

 therefore looked upon the gelatinous matter, which, after 

 edulcoration and desiccation, was found to possess the most 

 distinguishing properties of siliceous earth, as newly formed 

 from the water and acid. In short, Mr. Scheele considers 

 both the crust which forms upon the water during the dis- 

 tillation of the spar and the siliceous earth obtained by pre- 

 cipitation as an earthy substance originating from the acid of 

 fluor arid water. 



SECTION IV. 



Since the appearance of Mr. Scheele's Essay, many hands 

 have been set in motion by the singular phenomena related 

 in it. Boullanger was probably led by the volatility of this 

 acid, and the strong smell of pure marine acid, which the 

 liquor emits after distillation, to look upon the acid of fluor 

 as an acid of sea-salt. Monnet and Priestley, on the other 

 hand, declared in favour of the vitriolic acid. With respect 

 to the earth, Margraaf and Achard supposed that it must 

 proceed from the fluor itself, and constitute an unknown 

 species. Professor Weigel maintains that it has its origin in 

 a decomposition of the acid. Such are the principal opinions 



