39 



tluit when a metal is hroiiulil lo soliuioii l»\- an eleclrolvlic wav, so 

 when it is inaile into an anode, the internal ecinilibrinni will be 

 disturbed, and the metal will become superficially onobled, at least 

 when the velocity of solution is greater than the velocity with which 

 the internal e(|uilibriuni sets in. In this case therefore the dissolving 

 metal will have to become positive with respect lo an auxiliary 

 electrode of the same metal which is superficially in internal equi- 

 librium. If reversely the metal is made to deposit electrolytically, 

 the reverse will take place, and the separating metal will be less 

 noble and therefore negative with lespect to the auxiliary electrode. 



The anodic disturbance of equilibrium being attended with a dimi- 

 nution of the more active kinds of molecules, this process will bring 

 about a diminution of the chemical activity. This is therefore the 

 reason that this anodic state of disturbance is a more or less passive 

 state of the metal. 



At the cathode the disturbance lies exactly in the other direction, 

 and a more active state will be brought abont. 



The degree in which a metal is thrown out of its state of equi- 

 librium in case of electrolytic solution or deposition, will depend 

 on the cnrrent density at constant temperature, and it was therefore 

 of importance to study the discussed phenomenon at different current 

 densities. 



What may be expected is this that the internal equilibrium will 

 generally be able to maintain itself for very small current densities. 

 Then the tension with respect to the auxiliary electrode will be 

 zero, both when the metal is anode and cathode. With greater 

 current densities the metal will get superficially more and more 

 removed from the state of internal equilibrium on increase of the 

 current density, and the tension with respect to the auxiliary elec- 

 trodes will greatly increase. 



As the metal surface gets further remoxed from the state of 

 internal equilibrium, so becomes more metastable, the velocity of 

 reaction which tries to destroy the raetastability, increases however 

 in consequence of the change of concentration in the homogeneous 

 phase; and we may therefore expect that the potential difference 

 between metal and auxiliary electrode will vary with the current 

 density in the way indicated in Fig. 1. 



When the velocity with which the internal equilibrium sets in, 

 is small, the part ah will lie at exceedingly small current densities, 

 and if the measurements are not exceedingly delicate, we shall get 

 the impression that this piece is entirely wanting. 



It is clear that the tension which is represented here as function 



