REFINING OF COPPER AND LEAD. 197 



power is contemplated exclusively of the space required, the 

 cost of installation, and the real cost price of the refining. 



The expenditure of power is, in fact, only one of the 

 economical elements of the question, and when waterfalls are 

 available it is often the least important one. The sizes of the 

 installations and the quantity of metal to be treated may be the 

 determining causes of the failure of a manufactory ; for the 

 interest on the capital absorbed may reach, and even exceed 

 the gross profits realised by the operation itself. When a 

 quantity of copper is refined with a given power, and it is pro- 

 posed to double the production without increasing the expendi- 

 ture of power, it becomes necessary to quadruple the quantity 

 of metal to be treated, which increases in a very great propor- 

 tion the cost of first establishment. The absorbed capital then 

 becomes considerable in proportion to the annual amount of 

 business. 



The limit beyond which it becomes necessary to increase 

 the capacity of the electric source is even much nearer than 

 would be at first imagined. A single really industrial installa- 

 tion has 120 baths, joined in series, worked from two dynamo- 

 electric machines, also joined in series, and we believe that this 

 proportion between the machines and the baths should not be 

 exceeded to remain in really economical conditions. 



It was Elkington, the inventor of industrial electro-silvering 

 and gilding, who first refined copper by means of alternating 

 rectified currents. The patents date from 1866, and do not 

 embody anything important as regards the composition of 

 baths or the use of electricity, but they are very explicit : 

 ' The raw copper," it is said, " constitutes the plate which 

 becomes dissolved in a suitable solution; pure copper is 

 deposited on thin surfaces connected to the negative pole as 

 the said plate is being dissolved. It is advisable to use a 

 series of vats, and to work the entire system with a magneto- 

 electric machine. The vats are charged with an almost saturated 

 solution of sulphate of copper." 



The electrolytic refining of copper has been practised for the 

 last ten years by the Norddeutsche Affinerie at Hamburg, by 

 Messrs. Oeschger & Mesdach at Biache, by M. Hilarion Koux 



