[ 4" ] 



add a few additional remarks on the principal che- 

 mical tcfts mentioned in the firft eflay, by way of 

 illuitration. 



ift. The moft exquifite ted of the prefence of 

 copper is the Volatile Alkali^ or Spirit of Sal Ammo- 

 mac. If ten or twelve drops of this fpirit be added 

 to any liquor impregnated with copper, it inftantly 

 exhibits a blue colour, in proportion to the quantity 

 contained. This elegant experiment has been car- 

 ried to an almoft inconceivable degree of minute- 

 nefs by the Honourable Mr. Boyky fo as to afford at 

 once, a ftriking exaipple of the excellence of the 

 teft, and the extrc:me divifibility of this metal. 



2dly. Another method is by precipitation with 

 iron. Thus if a piece of polifhed iron be immerfed 

 fome time in any fluid wherein copper is held in fo- 

 lution by the intervention of an acid, the acid, having 

 a ftronger attra6tion to iron, lets go the copper to 

 unite with it, and the copper is afterwards found 

 adhering to its furface in its Ihinlng coppery form, 

 as has been already mentioned. 



^dly. By evaporation of a large quantity of the li- 

 quor, and fubfequent calcination and reduSiion^ as 

 propofcd concerning lead.* 



• Eflay ii. p. 381. 



Thu& 



