WORK ABSORBED IN ELECTROLYSIS. 37 



another portion reduces a certain quantity of sulphate of copper, 

 with a precipitation of metallic copper.* 



The more constituents there are in the composition of com- 

 pound substances, the more causes of secondary actions there are 

 in a bath, and the comparatively smaller is the yield for any 

 given one of the said constituents. Thus with chloride of zino 

 we adopt a yield of 40 per 100, whereas with sulphate we will 

 not admit a yield of more than 30 per 100. 



Now as to the calculation of the electrolytical work. 



One equivalent of sulphate of copper is composed of 32 

 grammes of oxygen, 16 grammes of sulphur, and 31 "8 grammes 

 of copper ; 28 2 calories must therefore be expended for the 

 precipitation of 31 -8 grammes of copper. One kilogramme 

 would require 



1000 x 28-2 



31-8 



= 886 calories 



and W = 886 x 424 = 375664 kilogrammetres. 



To effect this work in one hour's time, with a yield of 30 per 

 100, an engine power of 



375664 



= 4 ' 33 horse - wer Wl11 be 



0-30 x 3600 x 75 



Theoretically 1'30 H.P. is sufficient. The number of 

 amperes must be 



_ looo __ R40 



0-00001036 x 31-8 x 3600 " 

 The number of volts is 



4-33x75x9-81 

 ~840~ 



So that 1"16 volt would have been sufficient for overcoming the 

 work of decomposition proper. 



OF THE CHEMICAL ACTIONS IN AN ELECTROLYTE. If it is 

 always easy to calculate the number of amperes required for the 

 liberation of a given weight of metal in a given electrolyte, and 

 when the chemical actions are known as also the useful work for 

 overcoming the counter electromotive force, it is, on the con- 



* Berthelot, Essai do mccanique cbiinique,' t. ii. p. 330. 



