PHYSICAL AND LITERARY. 223 



for the alkali is then immediately detached 

 from the acid : and agreeably to this I found, 

 upon trial, that a pure or cauftic volatile 

 alkali does not feparate a calcarious earth 

 from an acid. Yet, if we mix a mild volatile 

 alkali, which is a compound of alkali and 

 air, with a compound of. acid and calcarious 

 earth, thefe two laft, which attradt one an- 

 other mofl: ftrongly, do not remain united ; 

 but the acid is joined to the alkali and the; 

 earth to the air, as happens in the precipi- 

 tation of a calcarious earth from an acid,' 

 by means of the common or mild volatile 

 alkali. 



I remember likewife a parallel inftancc 

 with regard to quick-filver. This metal has 

 an attraction for the vitriolic acid, and when 

 joined to it appears under the form of turbith 

 mineral : but this attradtion is weaker than 

 that of the fixed alkali for the fame acid j 

 for if we mix a diffolved fait of tartar with 

 turbith mineral, the turbith is converted into 

 a brown powder, and the alkali into vitrio- 

 lated tartar; which change happens the 

 fooner, if the pure or cauftic alkali is ufed. 

 Yet, if to a compound of quick-filver and the 

 nitrous acid, we add a compound of the fixed 



alkali 



