Chemistry. — The Phenomenon after Anodic Polarisation.” 1. By 
Prof. A. Smits, G. L. C. La Bastipg, and J. A. vAN DEN ANDEL. 
(Communicated by Prof. P. Zreman). 
(Communicated in the meeting of March 29, 1919). 
Introduction. 
When the experimental electrical potential of iron is measured 
during the anodic polarisation, we observe that this potential becomes 
less negative as the density of the current increases. When this 
experiment is carried out in solutions containing few or no halogen 
ions, this phenomenon greatly increases above a definite density of 
current, and the iron then passes from the active into the passive 
state. Though this transition from the active into the passive state 
is not observed for all metals, all of them present, when they are 
anodes, a potential that is shifted more or less in the positive direction. 
This phenomenon of the anodic polarisation, like that of the cathodic 
polarisation, has been explained in a simple way by the recent 
views about the electromotive equilibria’). 
A new phenomenon, however, presented itself when somewhat 
more than two years ago Smits and Losry pe Bruyn made use of a 
rotating commutator according to Le Branc?) during the anodic 
polarisation of iron. 
This commutator is constructed so that the potential difference - 
is not measured during the passage of the current, but immediately 
after the current has been broken. With this method of procedure 
the remarkable phenomenon was discovered that when the current 
density was not so great that the iron became passive, the iron did 
not show a less negative, but a more strongly negative potential, 
which means that the iron exhibited a change of the potential after 
anodic polarisation in a direction opposite to that which was to be 
observed during the passage of the current. | 
At first it was supposed that this phenomenon had to be attributed 
to some mistake in the arrangement of the experiment, but it soon 
appeared that this was not the case, and that the same phenomenon, 
but slightly modified, also appeared for nickel, and as Dr. ATEN 
found afterwards, also for chromium *). 
1) Zeitschr. f. phys. Chem. 92, 1 (1916). 
2) Zeitschr. f. phys. Chem. 5, 469 (1890). 
8) These Proc. XX, 1119. 
