REFINING OF COPPER AND LEAD. 209 



work for the past four years, the others have been installed 

 more recently. 



In order to give a low internal resistance and a great power 

 in amperes, the maker has surrounded the soft iron and the 

 bars of the electro-magnets with copper bars of rectangular 

 section, instead of winding them with wire, as in machines for 

 light or transmission of energy. 



The induced bobbin is provided with a single series of bars, 

 with the Hefner- Alteneck system of winding. The corresponding 

 bars are joined together by means of large spiral bands situate 

 on the face of the bobbin opposed to the collector. On the 

 anterior face of the bobbin, on the collector side, the bars are 

 connected to the latter by means of strong copper angle pieces 

 (Fig. 34). 



The inductor is also composed of a single layer of copper 

 bands coiled by series of seven on each branch, or twenty-eight 

 in all. The transversal section of these bars is 13 square 

 centimetres ; the junctions are bolted and soldered together in 

 order to secure good contacts. 



The insulation of the bars is" effected by means of asbestos, 

 which, owing to its non-conductivity, allows the machine to get 

 heated without danger. The machines used at Oker's reach to a 

 high temperature without any other inconvenience than that of 

 increasing their resistance, and consequently the motive power 

 necessitated for the precipitation of a given weight of copper. 



Each of these machines feeds ten to twelve large vats, and 

 refines from 240 to 300 kilogrammes of copper per day (about 

 1 kilogramme per hour per vat). The power required for 

 the production of the current is from 10 to 12 horse-power, 

 corresponding therefore to 1 horse-power per vat. 



The internal resistance of these machines is 00075 ohm, the 

 electromotive force from 3 to 6 volts, the intensity from 810 

 to 1000 amperes. The total resistance of the baths and of the 

 conductors is about 0055 ohm ; the relation between the 

 internal and external resistance of the machine therefore is 

 00075 _ 1 

 0055 = ~7' 



We do not possess any further detailed particulars respect- 



p 



