SILVER. 



263 



with common salt, in order to convert it into chloride. 

 Iron is subsequently employed to remove the chlorine, 

 and isolate the metallic silver. 



Give the com- 658. Mercury is added with the iron, in 

 piete process. orc j er ^^ j t ma y dj sso i ve the silver from 



the mass of roasted ore and iron, as fast as it is formed' 

 The materials are agitated with water for many hours 

 together. At the end of the process the mercury, with 

 its load of silver, is drawn off from the bottom of the 

 cask. The solution of silver in mercury is afterward 

 filtered through buckskin or closely woven cloth, which 

 allows a large part of the liquid metal to pass, while 

 the silver with a small portion of mercury is detained. 

 The silver is then freed of its remaining mercury by 

 heat. The above process is called amalgamation. 



659. SILVER OBTAINED FROM LEAD. 



Describe the 



process for Almost all lead, as produced from galena 



and its other ores ' contains a certain pro- 

 portion of silver. The latter metal may 

 be freed from a large part of the lead by melting the 

 alloy and then allowing it to cool slowly. Most of 

 the lead solidifies in small crystals, and may be skim- 

 med out with an iron cullender. An alloy containing 

 silver in large proportion remains in the liquid condi- 

 tion. It is afterwards solidified by further cooling. 

 The above is called Pattinson's process. 



660. CUPELLATION. The remainder of 

 How is the re- j eac [ j s separated from the silver by con- 



maimng lead 



separated? verting it into oxide, in a current of heated 



air. The silver does not oxidize under 



these circumstances, but retains the metallic form. 



