272 Dr. C. R. A. Wright on the Determination of 



" polarization " of the voltameter increases until it differs 

 from the E.M.F. of the electromotor by only a very minute 

 quantity. With boiled acid, and especially in voltameters 

 so constructed that neither the oxygen evolved at the + 

 electrode nor the external air can reach the — electrode 

 (saving by unavoidable diffusion), the rate of the diminution 

 of the current is much greater than is the case when these 

 conditions are not fulfilled. On trying experiments of this 

 class, however, it was found that even with the most carefully 

 constructed voltameters the current never became too small 

 to measure, even after many weeks ; it gradually subsided to 

 a limiting value, below which it never sank (i. e. as long as 

 the E.M.F. of the electromotor and the resistance of the 

 circuit remained the same). No trace of gas, however, was 

 evolved at either electrode ; which was evidently due to the fact 

 that, owing to " diffusion discharge," the hydrogen and oxygen 

 evolved by the current became reconverted into water just as 

 rapidly as they were generated, by the current ; so that the 

 particular final steady current attained with any given ap- 

 paratus measured the rate of diffusion discharge with that 

 apparatus under the particular conditions of the experiment. 



84. On comparing such results with different electromotors, 

 it was at once perceived that w r hen the resistance in circuit re- 

 mained the same, the greater the E.M.F. of the electromotor the 

 greater was the value of the final steady current that passed, 

 although as long as the E.M.F. of the electromotor did not exceed 

 a certain limiting value (different for each form of apparatus) 

 no visible evolution of gas took place in any case ; pari passu 

 with the increase in the strength of the current, the counter 

 E.M.F. setup was found to increase; that is, the value of 

 e = E — CR, where E is the difference of potential between the 

 electrodes, C the current, and R the resistance of the column 

 of fluid between the electrodes (Part III. § 57). Thus the 

 following values were obtained w r ith voltameter No. 1 above 

 described (§ 80), and precisely analogous ones with the others. 

 Final steady current. Value of e. 



0*1 microw r eber. 0*140 volt. 



0-13 



0-297 



0-24 



0-468 



0-5 



0-615 



0-8 



0-929 



1-2 



1-395 



2*3 microwebers 



1-523 



3-1 



1-564 



4-0 



1-663 



With this particular voltameter currents of greater magnitude 



