401 



Ni — 0.630 V 

 Pt (/ƒ,) — 0.640 V 



and the nickel electrode had therefore again assumed the Hj-potential. 



That in this measurement the H-ion concentration must be smaller 

 than i()~-^ follows fiom an analogous determination with an NiSO^- 

 solution boiled out in vacuum and acidified with H^SO^ as electrolyte. 



The Ni-potential was now constant at — 0,317 F immediately 

 after the boiling. 



On conduction of H^ through the same solution — 0,315 V was 

 found later for the Hj-potential. 



4. When we consider the different determinations of the equili- 

 brium potential of Ni, the following facts are worth noticing : 



Neumann ^) finds — 0,538 V for electrolytic Ni, hence Ni charged 

 with H, and disturbed towards the base side. He does not speak 

 about the atmosphere in which the determination has been made. 



Pfanhauser '^) and Siemens ^), who worked in the same way as 

 Neumann, found values deviating comparatively little from the 

 real value. 



Muthman and Frauemberger *) find — 0,880 V as most negative 

 value for nickel charged with Hj, which value they took for the 

 equilibrium potential. The values found by Pfanhauser and Siemens 

 can probably be explained by this, that two counteracting influences, 

 the H, charge and the air atmosphere, compensated each other. 

 Pfanhauser could only obtain the most negative value — 0,466 V 

 found by him when the electrode was measured in the vessel in 

 which it was formed by electrolysis. Transmission through the air 

 always yielded less negative values. 



Rustere) found — 0,800 V as minimum value for the tension of 

 separation of nickel. 



Schweitzer ") carries out the measurement in the Hj-atmosphere, 

 because he wanted to exclude the influence of 0,. He finds — 0,616 F, 

 a value, which as was set forth above, is not the equilibrium potential, 

 but a value which is determined by the H-ion concentration in the 

 electrolyte used. 



^) Z. phys. Ghem. 14 []894J '21b. 

 2) Z. f. El. Chem. 7 [1901] 698. 



5) Z f. Anorg. Ghem 41 [1904] 249. 



4) Sitz.ber. Bayr. Akad. Wiss. 34 [1904] 201. 

 ») Z. f. El. Chem. 7 [1900] 257. 



6) Z. f. El. Chem. 15 [1909] 602. 



