Chemical Affinity in terms of Electromotive Force. 



189 



throughout, and the U-tube being the same ; so that diffusion 

 must have gone on at as d early as possible the same rate 

 throughout. The numbers in the column headed " largest ' ' were 

 obtained with electrodes each exposing 27*5 square centims. 

 surface ; those in the columns headed " medium " and "small- 

 est " with electrodes exposing respectively 3'2 and 0*2 square 

 centims. of surface. In every case the value of CR was prac- 

 tically inappreciable. 



(I.) Value of E on breaking circuit =1*60 volt. 



Fall of E in volts. 



Time, in seconds. 



Largest. 



Medium. 



Smallest. 



5 



•05 



■09 



•19 



10 



•08 



•13 



•27 



20 



•10 



•17 



•37 



30 



•12 



•20 



•46 



60 



•15 



•26 



•61 



120 



•19 



•33 



•75 



180 



•22 



•35 



•8-1 



(II.) Value of E on breaking circuit = 1'05 volt. 



5 



less than '01 



•03 



•17 



10 



•01 



•04 



•25 



20 



•02 



•05 



•31 



30 



•03 



•06 



•37 



60 



•04 



•07 



•44 



120 



•06 



•09 



•49 



180 



•07 



•10 



•52 



It is evident from these numbers, specimens of many similar 

 experiments, that the predictions from the general theorem 

 mentioned in § 69 are completely verified by experiment. It 

 maybe noticed in passing that with the "largest" voltameter, 

 when the value of E on breaking circuit was below 1 volt, the 

 minimum rate of fall of polarization was so slow that no 

 visible motion of the spot of light occurred even during many 

 seconds, and with still lower values of E even after several 

 minutes. 



72. The following experiments are also of interest in con- 

 nexion with this subject, as indicating how the rate of fall of 

 polarization is affected not only by the removal of the auraa 

 of gas round the electrodes by diffusion from one to the other 

 of fluid containing dissolved gas, but also by the solution of 

 the aura in the fluid itself (if not saturated with the gas con- 

 stituting the aura), and also by the passage of gas into or out 

 from the interior of the electrode, thus causing a diminution in 

 the aura or vice versa. Platinum- or gold-foil electrodes of 

 various sizes being arranged in U-shapecl voltameters like those 

 just described, a gentle current was passed for some days, so as 



Phil Mag. S. 5. Vol. 11. No. 07. March 1881. ' P 



