380 



disturbance, passes fhrough the point c'' , ov in other words at the 

 moment that the distin'bance of tiie platinum electrode has increased 

 to such an extent that the potejitial ditference is indicated by a 

 horizontal line passing Ihi'ongh c". 



'_L-A'-0 



A + 



This would, however, be the case when the hydrogen could have 

 assumed internal equilibrium in the metal surface, and when there 

 was, therefore, no supertension. As was already said the supertension 

 is just to be explained by this that also the establishment of the 

 internal equilibrium of the hydrogen cannot keej) pace with the 

 ion-separation. Hence the hydrogen appears as second phase for the 

 first time not when the potential difference of the metal phase has 

 risen to c", but to a higher point, e.g. c'. In correspondence with 

 the concentration of the electrolyte, the curves <i'c and b"c intersect 

 in this point, which curves refer to the electrolytes which can 

 coexist with a disturbed hydrogen phase, resp. platinum phase. 



The hydi-ogen phase (/', which therefore is generated, is a disturbed 

 hydrogen phase, as it contains more hydrogen-ions and electrons 

 than corresponds with the state of internal equilibrium. 



The supei'tension can now directly be read from the figure; it 

 is equal to the distance c'c". 



Now it should be borne in mind that the point c practically 

 coincides with the hydrogen axis, and that when a platinum elec- 



