REFINING OF COPPER AND LEAD. 225 



0-0020x5 



and for the 40 baths 0*0184 ohm. 



At Hamburg (we only take into consideration the last two 

 installations, as they constitute a progress on the first one), 

 we will determine the distance between the anodes and the 

 cathodes, knowing the resistance of one bath. 



This resistance is equal to that of a copper wire 5 milli- 

 metres diameter and 1 metre long, that is to say 00084 ohm 

 for one bath, and 1 ohm for 120 baths. 



The surface of anodes being 15 square metres per bath, the 

 resistance per square metre is 0*00084 ohm x 15 = 0-0126 

 ohm, the distance between the anodes and the cathodes is 

 therefore : 



0-0126 



* 

 u 



a 

 = 3 centimetres. 



At Birmingham the average distance between the electrodes 

 is 6 centimetres, and the surface of anodes per bath 2 raq 80 ; 

 the resistance of one bath is therefore : 



A X 6 = 0-00428 ohm per bath, 



'oil 



and 0-20544 ohm for the 48 baths. 



The electrical work performed by the passage of the current 

 through these various resistances is easy of calculation when 

 the intensity of the said current is known. For instance we 

 have seen that at Marseilles 10 '40 kilogrammes of copper were 

 precipitated per hour in 40 baths, that is to say, 260 grammes 

 per bath per hour ; at Hamburg the deposition per bath per 

 hour is 312 grammes, and at Birmingham 270 grammes. 



We also know that each ampere liberates 1 18 gramme of 

 copper per hour ; the intensity of the current therefore is : 



C = TTjo = 220 amperes, at Marseilles. 



312 

 G! = _ YQ = 265 amperes, at Hamburg. 



1 * lo 



270 

 ^2 = r~V6 == 230 amperes, at Birmingham. 



1 * lo 



