PARTING. 221 



washed, and may be melted into an ingot. It is 

 called parted silver. When this silver has been ob- 

 tained from a mass which had been refined by lead, 

 and when it has been well washed from the solution 

 of copper, it is very pure. Or the silver may be 

 separated from the nitric acid by adding to it mu- 

 riatic acid, with which it forms muriate of silver. 

 Muriate of silver may be decomposed by mixing it 

 with soda, and exposing it to a sufficient heat in a 

 crucible, whereby the soda unites to the muriatic 

 acid, and sets the silver free. 



The refiners frequently employ this solution of 

 copper obtained in the process of parting, for 

 making verditer ; which is prepared by adding 

 quick lime to the solution ; a precipitate takes 

 place, which is the blue pigment known by the 

 name of verditer. 



Parting gold from silver by cementatio7i. — This 

 is also called parting by concentration, and is 

 usually employed when the quantity of gold is so 

 great to that of the silver, as to render it a difficult 

 task by aqua fortis. The mixed metal to be 

 cemented is to be reduced to plates, as thin as 

 small pieces of money. At the bottom of the cru- 

 cible, or melting-pot, is to be laid a stratum of 

 cement, composed of four parts of bricks powdered 

 and sifted, one part of green copperas (sulphate of 

 iron) calcined to redness, and one part of common 

 salt, about the thickness of a finger in depth. Upon 

 this stratum a layer of plates of the metal is to be 

 placed, and then another stratum of cement, and 

 so on till the crucible is filled. It is now to be 

 placed in a furnace, or oven (after a top has been 

 luted on the crucible,) and exposed for twenty- 

 four hours, till it is gradually made red hot, but 

 by no means to be melted. The fire is now left to 



