232 ELECTROLYSIS. 



not as cheap as some people fancy. The lubricating and main- 

 tenance of the motor, the repairs to the valves, the over-fall, 

 the canals of derivation and the mill race are the cause of an 

 annual expenditure which sometimes proves very important. 

 We know of some factories where the hydraulic power costs as 

 much as that supplied by a steam engine with fuel at 10 and 

 even 15 francs per ton. The flow of water is generally irregular, 

 and it often happens that the adjunction of a steam engine is 

 necessitated in order to prevent a partial stoppage of an esta- 

 blishment situate on a watercourse. This naturally increases 

 the cost of first establishment, and consequently the total ex- 

 penditure per ton. 



By combining together all the best possible arrangements 

 hydraulic power, large number of baths in tension, minimum of 

 copper under treatment, &c. we believe a manufacture could be 

 established in which the cost of refining copper would not ex- 

 ceed 150 francs per ton (6Z.) ; but it would be difficult, if not 

 impossible, to obtain it at a lower price, and especially if nothing 

 was neglected in order to obtain very pure copper of a high 

 electric conductivity. 



In conclusion, the refining of raw copper by means of elec- 

 trolysis necessitates much space, considerable sums of money, 

 and is a very expensive process. It is only just to add that 

 raw coppers generally contain a small proportion of gold and 

 silver, and that the cost of refining is often compensated, and 

 even more, by the value of the sub-products ; * on the other 

 hand, the copper is much purer than that obtained from metal- 

 lurgical treatment, and its high conductivity renders it a much 

 more valuable metal. 



REFINING or LEAD. 



The following is, we believe, the only process applied to the 

 industrial refining of lead. 



The inventor is Mr. Keith. The Company working his pro- 



* The sale price of raw copper to refining works has naturally been affected by 

 the knowledge that they contain a proportion of precious metals ; but in general 

 the industry benefits by this treatment, owing to which excellent coppers are 

 offered in the market at comparatively moderate prices. 



