399 



fastened in a glass lube by means of sealing-wax], a platinized 

 Platinum electrode, which could be immersed in the liquid just 

 before the measurement, a bevel, which was in connection with 

 the calomel electrode, and a supply and exit tube for ihe hydrogen. 

 In the middle tube there was placed a stirrer with mercury closure 

 to make stirring possible if necessary. Yery pure hydrogen which 

 was obtained by leading the hydrogen from a cylinder oi- from an 

 electrolytic hydrogen apparatus (with nickel electrodes) through a 

 glass tube with Pt-asbestos, which was heated up to ± 500° in 

 a furnace, and then through two blown washing bottles with a 

 suspension of Fe(OH),, was tirst led through and later ovei- the 

 NiSO^ solution, while from time to time the potential differences of 

 the different electrodes were measured. 

 The result was: 



Ni- 0.640 V 1 electrolyte 2,hnNiS0,; potential 

 Pt — 640 V \ with respect to 1 n calomel-electrode. 



As folloios fro7n Wilsmore's ^) calculation and Schoch's determi- 

 nations '^), as also from determinations made hy us, the equilibrium 

 potential of Ni lies at ± — 0,48 V loith respect to 1 n calomel 

 electrode. Hence the above found nickel potential is not the eqidlibrium 

 potential, but the potential of a state disturbed superficially in the 

 base direction. We see here that the nickel has assumed the .same 

 potential as the H^-electrode, ivhich is in agreement with the above 

 given theoretical derivation. 



When we consider the solutions of NiSO^ with increasing H-ion 

 concentration by continually adding more H^SO^, we see that the 

 equality continues to exist also for other values of the H-ion con- 

 centration : 



On measurement in hydrogen atmosphere the found Ni- potential is 

 accordingly quite dependent on the H-ion concentration, and always 

 equal to the H^ potential. 



Before going on we will anticipate and mention already here that 

 according to the here given theoretical considerations the potential 

 of the unary nickel, or the nickel in internal equilibrium, 

 can only be measured in a solution in which the electron concen- 



1) Z. phys. Ghera. 35 [1900] 291. 



2) Amer. Ghem. J. 41 [1909] 208. 



