INDUSTRIAL ELECTRO-CHEMISTRY 149 



works in Newark. To-day there are in operation in this 

 country ten electrolysis refineries with a total daily copper out- 

 put of 764 tons, or 279,000 tons per year. At the same time 

 27,000,000 ounces of silver and 346,020 ounces of gold are 

 recovered per year in these refineries. 



There is a very peculiar difference in the details of oper- * 

 ation of the different refineries. Two plants use the series 

 arrangement of electrodes, all others the multiple system. 

 There is a considerable difference in the current density used ; 

 of two plants in the west, in close proximity, one uses 40, 

 the other 12 amperes per square foot. The list of variations in 

 the methods of operation could be easily enlarged. In other 

 words, the art of copper refining is far from being standard- 

 ized. Since it is known that for a number of years the differ- 

 ent refineries have very carefully and systematically studied 

 the best conditions of operation in their own case, the difference 

 in the methods of the different refineries may be attributed 

 to a difference in the given conditions in each case. If 

 this is so it emphasizes the complexity of the economical 

 working of even so simple an electrolytic problem as copper 

 refining. 



Recently the Betts process of lead refining has aroused 

 very great interest. The essential point is the electrolyte, 

 which is a solution of lead fluosilicate, containing an excess 

 of fluosilicic acid. It is easily prepared from inexpensive 

 materials, it conducts the current well and it dissolves other 

 metals but lead only in very small quantities. The last point 

 is of great importance in view of the fundamental require- 

 ment that the solution should remain pure during operation. 

 In a similar way, for copper refining, the possibility of con- 

 tinually renewing the electrolyte is essential. 



The Wohlwill process of gold refining is in operation at 

 the Philadelphia mint, using an electrolyte of gold chloride, 

 rather strongly impregnated with free hydrochloric acid. 

 The addition of the free hydrochloric acid in this case, like 

 that of fluosilicic acid in the Betts process, is necessary to 

 produce the proper corrosion of the anode and to maintain 

 the electrolyte in its original condition. Much special study 

 has been devoted in recent years to the question under what 



