REFINING METALS. 



cible, unless great care be used ; nevertheless, this 

 method has its advantages, being much more expe- 

 ditious than cupellation. 



Separating Silver from Copper by Eliquation. 



When it is desired to separate, in the large way, 

 a small quantity of silver from much copper with 

 which it is alloyed, the process called eliquation is 

 resorted to. This operation is grounded on the 

 nearer affinity of silver with lead than with copper ; 

 in consequence of which it fuses, and combines with 

 lead at a degree of heat in which copper continues 

 unfused. 



Whitening Silver by Boiling. 



Whitening of silver by boiling is one of the me- 

 thods of parting copper from silver in the humid 

 way. For this purpose, silver wrought in any 

 shape is first ignited to redness, and afterwards 

 boiled in a ley of muriate of soda, and acidulous 

 tartrite of potash. By so doing, the copper is re- 

 moved from the surface, and the silver receives a 

 better appearance. 



Precipitating Silver by Copper. 



Copper has a much greater affinity with oxygen 

 than silver ; consequently, the silver is precipitated 

 from its solutions as a fine silver dust, by metallic 

 copper. This likewise affords a means to discover 

 what portion of silver may be contained in an alloy 

 of silver and copper. A quantity of the mixture 

 determined by weight is dissolved in nitric acid j 



