Alternate Current Electrolysis. 407 



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" Alternate Current Electrolysis." By J. HOPKINSON, D.Sc., 

 F.R.S., E. WILSON, and F. LYDALL. Received November 2, 

 Read November 23, 1893. 



Our attention has been called to the interesting work of Messrs. 

 Bedell, Ballantyne, and Williamson on "Alternate Current Con- 

 densers and Dielectric Hysteresis," in the ' Physical Review ' for 

 September October, 1893. As experiments bearing upon an ana- 

 logous subject were carried out in the Siemens Laboratory, King's 

 College, London, we think it may be of interest to publish them. 

 Our experiments were commenced in June, 1892, and were discon- 

 tinued in the following July with the intention of resuming them at 

 a future time. They are therefore not exhaustive. 



Suppose an alternating current to be passed through an electrolyte 

 between electrodes, and that the current passing and the difference of 

 potential are measured at intervals during the phase. If the elec- 

 trolytic action were perfectly reversible, we should expect to find 

 the potential difference to have its maximum value when the current 

 was zero, that is to say, when the total quantity of electricity had 

 also a maximum value. One object we had in view was to ascertain 

 if this were the case, and, if not, to determine what amount of energy 

 was dissipated under different conditions. 



This is readily done, inasmuch as the work done on the voltameter 

 or by the voltameter in any short time is the total quantity of 

 current passed in the time multiplied by the potential difference. 

 Let a curve be drawn in which the ordinates are the coulombs and the 

 abscissae the volts at corresponding times : the area of this curve re- 

 presents the work dissipated in a cycle. 



It is, of course, well known that if a current is passed through an 

 electrolyte, the potential difference speedily attains a certain maxi- 

 mum value and there remains. If an alternate current is passed, we 

 should expect to find that as the number of coulombs passed in each 



VOL. LIV. 2 F 



