REFINING OF COPPER AND LEAD. 211 



ing the installation. The foregoing demonstrates that the 

 management of the Oker Foundry would not sink such an 

 important capital as in the case of the works which we have 

 described. The electrolysed copper appears to be difficult of 

 refining, for the ' Electrotechnische Zeitschrift,' which first 

 described the Oker Works, makes the following remarks : 



"These figures relate to cupric solutions containing not 

 more than one-half per 100 of impurities. The polarisation 

 produced in the vats is greater in proportion to the degree of 

 impurity of the solution ; and the work required to overcome 

 this polarisation, which is at its maximum when liberation of 

 gas, that is to say, decomposition of water, occurs, is also 

 proportionally greater." 



ECONOMICAL CONDITIONS OF ELECTRIC REFINING. After 

 having given a general idea of the processes employed in 

 copper refining, and briefly described a few of the principal 

 installations in which these processes are in use, we think it 

 will be interesting to examine what are the conditions to be 

 fulfilled in the establishment of a factory working economically, 

 that is to say, in which copper is refined at the least possible 

 cost. 



In order to be in a position to formulate these conditions, it 

 is necessary to review a few accessory questions, such as the 

 maximum intensity of the current per metre of surface of 

 electrodes, the resistance of the baths of sulphate of copper, 

 the capital to be invested for a given production, &c., &c. The 

 first of these questions is of the greatest importance, as it is 

 the point of departure in all projects of installation for refining ; 

 we will therefore treat it with an exceptional development. 



M. GRAMME'S EXPERIMENTS. M. Gramme has carried out 

 various experiments on sulphate of copper baths with soluble 

 and insoluble anodes. The following is extracted from a note 

 presented by him to the Academy of Sciences on the 29th of 

 August, 1877. 



When, after the creation of industrial dynamo machines, it 

 was thought of using them for the operations of electrolysis, the 

 customs of the factories where it was proposed to change the 

 source of electricity had to be taken into consideration, and as 



P 2 



