694 



passivity. If a metal is once passive, it can undoubtedly be covered 

 by an oxide coat on anodic polarisation, but the formation of this 

 coat is a secondary phenomenon. 



Leaving apart whether on anodic pohirisation oxygen charges 

 give rise to a certain rise of the potential, it should be borne in 

 mind that it is exactly the ork/i?i of these gas charges that is to be 

 explained. Only when the metal during the passage of the current 

 undergoes a rise of the potential and the tension of generation of 

 the O2 is reached, these gas charges can arise, and so a theory 

 which purposes to explain the phenomenon of passivity, will have 

 to account for this potential rise. 



It follows from this that the theories of Fredeinhagen, Muthmann, 

 Frauenberger and others leave the essential part of the passivity 

 phenomenon an open question. 



3. Our experiments have proved that the phenomenon of 

 passivity resides in the metal itself, and that though this phenomenon 

 is decidedly a phenomenon of retardation, this retardation is not a 

 retardation of the ion hydiatation in the electrolyte, as Le Blanc 

 thinks, but a retardation oi' the ion transformations in the metal- 

 surface. 



4. It is perfectly true, as Grave states, that hydrogen accelerates 

 the setting in of the electromotive equilibrium. That the hydrogen 

 would accelerate the setting in of the Aö^^m/é/ié^oï^ó' equilibrium metal- 

 electrolyte, is an untenable supposition. 



The hydrogen accelerates the establishment of the homogeneous 

 internal equilibrium, but has often appeared to be inadequate to 

 neutralize the disturbance of the equilibrium brought about by etching. 



5. With regard to Finkelstein's (Khüger's) view it might be said 

 to be implied in the new conceptions to which the theory of allo- 

 tropy has led, but that the said observers, not understanding the 

 deeper signiücation and the drift of their assumption, were not 

 able to embody their view in a theory. 



6. W. J. Müller's views, which are only distinguished from 

 those of FiNKELSTEiN (Krügek) by the assumption that the states of 

 different valence formed different phases, are theoretically incorrect, 

 and have therefore not led to any result either. 



7. The trustworthy experimental data about passivity mentioned 

 in the literature, just as the new results in this department described 

 here, can all be easily explained by the application of the theory of 

 allotropy to the electromotive equilibria. 



Anorg. Chem. Lab. of the University. 

 Amsterdam, Sept. 25, 1914. 



