CHARGE OF A CONDENSER AND POLARIZATION OF ELECTRODES. 493 



electrode. The simplest method of measuring this constant will be 

 to connect it like a condenser with a battery of known electromotive 

 force less than the maximum electromotive force of polarization, and 

 then to measure the charge obtained, when the voltameter is closed 

 by a galvanometer. This method was used by Varley,* but it is 

 rendered difficult by this circumstance, that, as equilibrium is not 

 attained instantaneously either by charge or discharge, there is a 

 considerable loss owing to depolarization by diffusion. 



M. Blondlotf endeavoured to avoid this cause of error by first 

 investigating how polarization is set up as a function of the time of 

 charge. By means of a pendulum break (910), he connects the 

 voltameter with a known electromotive force for a very short time, 

 then short-circuits the voltameter by a very small resistance to de- 

 polarize it. The quantity of electricity corresponding to the charge 



Fig. 231. 



current is measured by the swing of the needle of a galvanometer. 

 By varying the time of contact, the curve of the changes as a func- 

 tion of the time may be constructed. This curve rises rapidly, and 

 without leakage would soon become horizontal ; it tends in short to 

 merge into the line AL (Fig. 231) the inclination of which with the 

 axis of the abscissae represents the leakage. The ordinate with the 

 origin OK measures the true charge which can give the electrodes a 

 difference of potential equal to that of the battery. 



The experiment being repeated with variable electromotive forces, 

 the curve representing the charges as a function of the electromotive 



VARLEY. Transactions of Royal Society, Vol. cvxi. p. 129. 1871. 

 BLONDLOT. Journal de Physique [i], Vol. x., pp. 277, 333, 434. 1881. 



