395 



As was already stated before, in this case we have to do with 

 the two following equilibria (in the liquid) 



Ni-^Ni- -\-2(9 

 and 



H^ ^ 2ff' + 2<9. 



When the electron concentration of the nickel equilibrium is 

 greater than that of the hydrogen equilibrium corresponding to a 

 hydrogen pressure of an atmosphere, hydrogen generation will have 

 to be found. 



We have : 



hence (//) must be > 10 -3. 



When therefore the hydrogen-ion concentration is more than 10'' 

 times the concentration in pure water, the metal nickel must give 

 hydrogen generation, which, however, is not the case. 



How to account for this will appear from what follows. 



For this purpose we consider here the equilibrium that we have 

 to do with in the system Ni — electrolyte, viz. : 



Nis'^Ais+ 2(9 s 



n n n 



Now we know that hydrogen generation occurs when the electrons 

 combine with the hydrogen-ions to hydrogen molecules. These 



26* 



