08^ 



l'hese phenomena being only observed above a certain current 

 densitii, it is clear that we liave to do here with a disturbance 

 whicli makes its appearance when the electric current is passed 

 througli with too great velocity. 



We have, therefore, to do here with a question of velocity, and 

 as an explanation of the primary character of the passivity pheno- 

 menon Faraday's oxide theory is to be rejected from the beginning. 



Witii regard to Grave's theory we may remark that it seemed 

 very improbable already at a cursory examination. Nernst has 

 namely demonstrated that in the phenomenon of solution equilibrium 

 of saturation always prevails in the boundary layer solid-liquid. In 

 connection with this w^e may, therefore, expect that this continues 

 to hold for the phenomenon of solution by an electrolytic way. 

 There is no reason at all to make an exception here. 



With regard to the second theory it should be observed that the 

 valence hypothesis, on which it is founded, is implied in the con- 

 clusions to which the application to metals of the theory of allotropy 

 leads. This theory generally concludes, namely, as was already said 

 before, to the existence of different kinds of ions in the metal phases 

 and points out that one of the possibilities is this that the metal ions 

 loith the same composition only differ in valence. 



The a[)plication of the theory of allotropy to the heterogeneous 

 electrolytic equilibria has further shown that when the metal phase 

 is comple.i', apart from the nature of the difference between the ions, 

 the anodic and cathodic polarisation, and also the passivity of metals 

 can be explained. 



Diametrically opposed to this theory are the theories 3, 4 and 5, and 

 it is now clear what will have to be decided. By an experimental 

 way we must try to get an answer to the question as to whether 

 the phenomenon polarisation and passivity resides in the boundary 

 surface between metal and electrolyte, as the theories 3, 4 and 5 

 suppose, or in the metal surface itself, as the theory of allotropy 

 has rendered probable. 



For this purpose the investigation about the complexity is the 

 obvious way. When experiment has proved the complexity, we can 

 try to find out whether it possesses metal ions of different valence. 



Experimental part. 



1. To examine whether or no the phenomenon of polarisation and 

 that of passivity resides in the metal surface, it seemed to us the 

 simplest course to attack the metal surface by means of chemical 

 reagents, and to see if it has changed its properties in consequence 



