385 



5 and 5a. The next ligiire G roters to the pheiioinenoii thai occurs 

 when the auxiliai'}' electrode is placed only 1 nun. under the liquid 

 level against the iron electrode, and from this we see how greatly 

 the activating intluence issuing from the iron at the level of the 

 liquid surface, disturbs the periodicity ; the regularity now consists 

 only in this that the most active state recurs at pretty regular times. 

 As might be expected the strength of the polarising current was 

 perfectly regularly periodic. 



Injiuence of the area of the surface on the periodic passivity. 



In conclusion we have examined what is the influence of an 

 enlargement of the immersed surface. For this purpose we have 

 made an experiment with a Spiral, of which 5 windings, with a 

 joint length of 60 cm. were immersed into the electrolyte. The 

 cathode was placed inside the windings, the auxiliary electrode being 

 placed against the second winding from above. While the strength 

 of the current was again regularly periodic, the potential difference 

 exhibited very irregular oscillations, as Fig. 7 clearly shows. The 

 irregularity was snch that even the most active state did not recur 

 regularly, and the whole curve, therefore, shows the periodicity 

 under the influence of great disturbances. Hence it could be clearly 

 perceived when observing the iron electrode, that this was never 

 passive resp active throughout the whole area at the same moment, 

 but that different parts were activated at different times. 



This curve is a very fine demonstration of the fact observed by 

 us already before that a piece of iron can be passivated with the 

 more difficulty as the surface is greater. 



Amsterdam, General and Anorg. Chemical 



June 27, 1918. Laboratory of the University. 



