Polarization at a Metallic Anode. 



665 



Time from start 



Current 



Current 



(mins.). 



(obs.). 



(calc). 







7*46x10-6 



7-4()Xl0-' 5 



30 



543 



5-59 



5*5 



520 



5-21 



140 



4(37 



462 



275 



4-23 



415) 



500 



3-88 



3-81 



82 



3-45 



350 



179 



2-95 



3-00 



250 



2-76 



2-78 



755 



205 



2-08 



In calculating the numerical values of the polarization from 

 (29), it must be remembered that mercury exists in solutions 

 of mercurous nitrate as a double ion Hg — Hg with twice 

 the usual ionic charge. This has been conclusively demon- 

 We must therefore put for e the value 



strated by Og^* 



6 = 2 x 9654 E.M. units per gramme-ion of Hg 2 . 



The 



ionic 



velocity U is not known with accuracy for 

 mercury, but judging by the conductivity it is slightly less 

 than that of silver. I have consequently taken it to be 



U = 5 x 10 -12 cm. per sec. per E.M. unit per cm. 



Since it only occurs after a logarithm sign, a fairly large 

 error in this value will only affect the result to a small extent. 

 The sectional area of the tube round A was 0*789 sq. cm.. 

 temperature 16° C, and the concentration of the mercurous 

 nitrate O'OOOl normal. Introducing these values into equa- 

 tion (29), we obtain 



V»ie ='0286 log 10 {1 + 2-34 x 10 5 (C + '395 x 10" 6 ) s/1} volt, 



where < 1 is expressed in amperes, and t in minutes. 



A comparison of the polarization calculated from this 

 equation with that obtained in the experiment is given in 

 the following tabic The numbers in the column headed 

 (V + CR AB )obs. are the observed differences of potential 

 between the electrodes A and B at the times given. Since 

 the resistance between A and B as measured by the tele- 

 phone and bridge was 1480 ohms, the true polarizations, 

 given under V,,,,.., are obtained by subtracting 1480 0" from 

 the numbers in the previous column. 



Zeit Vhys. Chem. xxvii. p. 285 ( 1898). 



