and 



398 

 A^^ln~-\ (9) 



A=^t^ln—^' (10) 



' F i^ü 



From which follows that the electromotive force of a circuit con- 

 sisting of these two metals immersed in the corresponding salt 

 solutions is : 



Let us now apply the just found relation (8), then we get : 



A —A —-^ ^ ^ -' In^-^ . . . (12) 



Now ii'i) is the same for different solutions with the same sol- 

 vent, so that we get : 



A, - A, ='-^^^;— ^ — ^/n^ • • • (13) 



The term: 



F 

 represents the volta-efïect, viz. : the potential difference that appears 

 when the two metals are brought in contact in dry condition. Now 

 we know that this potential difference is very small, so that this 

 equation (13) tells us that when the electron concentrations (<9/^,) 

 and {Ol^) have become equal, Aj — A^ will be very small or zero, 

 so that then 



will hold in first approximation. 



This result tells us, therefore, that finally the potential difference 

 nickel-electrolyte will have become equal to the potential difference 

 hydrogen-electrolyte. The experiment was, in fact, entirely in accord- 

 ance with this. 



3. An NiSO^-solution, in which a slight cloudiness had been 

 brought about by the addition of a little NaOH, to make the solu- 

 tion as little acid as possible, was brought in a vessel with 5 tubes. 

 These were closed by means of rubber stoppers, through which were 

 led two nickel electrodes [very pure Kahlbaum Ni-wire 3 mm. thick, 



