252 ELECTROLYSIS. 



Miest process. We have seen that by the Letrange process, 

 with the same power and in the same time, only 7 kilogrammes 

 could be precipitated. If things occurred exactly as the 

 inventors would have it, there would therefore be a great 

 advantage in using agglomerate ores ; unhappily, it is scarcely 

 possible to maintain the electrolyte at a certain degree of 

 saturation and composition, and the results are far from being 

 satisfactory. We believe that this treatment also has never 

 left the field of experiment and expectation to enter into that of 

 a really industrial practice. 



The principal defect of the preceding method is in the 

 neglect with which the composition of the electrolyte is 

 effected. In order to economise the motive power, Messrs. 

 Bias and Miest have taken soluble anodes without submitting 

 them to any preliminary chemical preparation. These anodes, 

 containing several soluble substances foreign to the body which 

 they had to precipitate, rapidly disturb the composition of the 

 bath. The laboratory experiments being particularly directed 

 towards the observation of the attack of the anode and the 

 metallic precipitation on the cathode, have been successful 

 enough ; but when the inventors attempted to produce on an 

 industrial scale they met with insuperable difficulties. 



The fact that it is the bath and not the anode which has to 

 be electrolysed should never be lost sight of. All the exertions 

 of the manufacturer must be concentrated upon that point : 

 ensure the constancy of the bath, and if they cannot obtain it 

 without incurring too considerable an expenditure, the best 

 plan is to abandon the electrolytic treatment and go back to the 

 ordinary metallurgical treatment. 



But before adopting such an extreme decision, they must 

 attempt to combine the two modes of treatment. For example, 

 instead of using the copper ores in their natural state, they 

 might be first reduced into mattes of an average percentage. 

 The purer pyrite Cu 2 S -f- Fe 2 S 3 contains 35 per cent, of copper, 

 but it is always mixed with iron pyrite which considerably re- 

 duces its percentage, the latter rarely reaching more than 7 to 

 8 per cent. An ore composed of sulphides, of sulphates and 

 oxides of the two metals, with a siliceous gangue, maybe obtained 



