Potential of Electrodes in Stationary Liquids. 41 



former value. If the first experiments are to be explained as 

 a result ot' local reduction of concentration at the cathode, 

 such reduction must therefore amount to at least 86 per 

 cent. 



Xow. in order to obtain an estimate of the magnitude of 

 depletion at the cathode that actually took place, we refer to 

 one of our experiments represented in fig. 11. Taking, for 

 example, curve 4, we have 



r=M84 mUam f . ''=«0", C„'= ^| m g" equiY - . 



cm.- rlo c.c. 



Employing equation (6), we find that if the liquid touching 

 the cathode is renewed completely after every second by 

 stirring, the loweriuo- of concentration could never go below 

 1*4 per cent. I have shown formerly"* that under more 

 unfavourable circumstances, viz.. when the cathode was 

 mercury contained in a cup, it is possible to prevent deple- 

 tion, which would require 0*4 sec. if the liquid were stationary: 

 it -eems improbable, therefore, that the lowering of concen- 

 tration in Haber's experiment went below the above value. 



By employing equations (5) and (7), we find that if the 

 concentration of the liquid be maintained continually at its 

 original value by stirring at ^ {) mm. distance from the cathode, 

 the utmost lowering that could take place would amount to 

 5J per cent. Brunnerf calculates the distance from the 

 electrode to which he was able to keep the concentration 

 unchanged in his experiments to have been 5 1 () to .} {) mm., 

 so that, adopting his values, we should conclude that the 

 lowering of concentration did not amount to more than about 

 H per cent. Starting from other curves on fig. 11, we 

 obtain similar values. In any case the results show that we 

 cannot assume changes of concentration amounting to <S6 per 

 cent, to have taken place in Haber's experiments, and that 

 the variations of electrode-potential with current-density 

 observed by him can therefore not be explained as the result 

 of concentration changes at the cathode. 



In carrying out the foregoing investigation the author has 

 been assisted by grants from the Chemical and Koyal Societies, 

 for which lie desires to express hi- indebtedness. 



Universitv College. Nottingham, 

 July 1904. 



* Loc. cit. p. 77. 



t Zeitschft. Vlnjs. Chem. xlvir. p. !>!> (1&04). 



