216 ELECTROLYSIS. 



circuit is proportional to the number of baths; from wliich it 

 might be concluded that with a fixed expenditure of work 

 it is possible by means of suitable arrangements to almost 

 indefinitely increase the total deposition. 



Fourth Series of Experiments. In a last series of experiments 

 M. Gramme has studied the effects due to the substitution in 

 sulphate of copper of insoluble lead anodes for soluble copper 

 anodes. As was to be expected, the polarisation was consider- 

 able, and the deposition of copper much less than previously, 

 since the work of decomposition of the sulphate of copper was 

 no more compensated by the formation of an equal quantity of 

 sulphate, resulting from the attack of the anode by the acid. 



All these experiments have been carried out with the utmost 

 care, as M. Gramme explains in his report to the Academy of 

 Sciences: "I have," he said, "placed myself in conditions 

 which I believe to be favourable for the measurement of the 

 work expended in each experiment ; the constancy of the work 

 was nearly perfect during the three hours \vhich each experiment 

 lasted ; I constantly verified it by galvanometric observations. 



" At the termination of the experiment I opened the circuit 

 and placed a Prony brake on one of the fly-wheels of the gas- 

 engine, bringing it back to the speed at which it ran during 

 the electrolytic operation, and I concluded from it what had 

 been the expenditure of work. 



" I could easily afterwards, by disconnecting the gas-engine 

 from the dynamo, ascertain what proportion of the motive power 

 was absorbed by the passive resistances of the latter. This 

 quantity is given in the above three tables. 



" I wished to go further, and ascertain the loss of work cor- 

 responding to the heating of the baths, and have arrived at the 

 results by the following means : 



"In every experiment I took both the initial and final tem- 

 perature -of the baths; an inactive bath placed 'near at hand 

 served as a means of comparison. The difference between the 

 final temperatures of the active baths and of the inactive one 

 represented the rise of temperature due to the current. 



" Taking into account this difference, as also the quantity of 

 the liquid operated upon, and the specific heat of the liquor, 



