ESSAY II. 



examine the arguments adduced by both these chemists in 

 favour of their respective opinions. 



SECTION III. 



Mr. Boullanger maintains that fluor acid precipitates 

 the solutions of silver and quicksilver, yielding with the 

 former muriated silver (vulgo luna cornua} ; and he asserts 

 that, by subliming half an ounce of the second precipitate, 

 he obtained mereurius dulcis. It is indeed true that the 

 fluor acid percipitates silver and quicksilver, as I mentioned 

 likewise in my Dissertation on the Fluor Mineral ; but the 

 precipitate obtained is in very small quantity (for the 

 fluor mineral, as well as all other mineral substances of a 

 calcareous nature, is adulterated with a small quantity of 

 muriatic acid) ; but the greatest abundance of the remain- 

 ing acid will not precipitate the above-mentioned metallic 

 solutions ; which, however, should happen if Mr. Boullanger's 

 opinion was true. He must have also made use of a very 

 large quantity of fluor acid, in order to obtain such a con- 

 siderable precipitate ; for, from the quantity of acid which 

 I obtained from 2 oz. of perfectly pure fluor, I procured only 

 half a drachm of luna cornua ; but I shall show how to 

 separate this small quantity of muriatic acid from that of 

 the fluor. A solution of silver made with nitrous acid is 

 to be precipitated with alkali of tartar ; and upon the 

 precipitate, after being edulcorated, so much acid of fluor 

 is to be poured as is requisite for giving an excess of acid, 

 and then the solution is to be filtered. Of this solution 

 of silver, so much is dropped into the fluor acid till no 

 more precipitation ensues, then the acid is filtered through 

 grey paper, and afterwards evaporated to dryness in a 

 glass retort. Water first comes over into the receiver ; 



