1128 



After the cnrrent had been broken, the potential was more active 

 than before the polarisation viz. — 0.667. In this the activating 

 action of the anodic pohirizalion after the interruption of tlie cnrrent 

 manifested itself again. When after this the cnrrent was suddenly' 

 again raised to 8 niA, the electrode became passive. Hence, while 

 on slow increase of the strength of the cnrrent the electi-ode resisted 

 8 inA, it could not bear this strength of current with rapid rise to 

 8 niA, notwithstanding the electrode was very active in currentless 

 condition. This is in harmony with the phenomenon described 

 before, that on quick increase of the cnrrent an electrode at first 

 presents a too positive valne, which afterwards becomes less positive. 

 By quick increase of the cnrrent the potential can now become so 

 positive, that the electrode becomes passive. If the current had been 

 slowly made stronger, so that the potential had every time an 

 opportunity to go back to less positive values, no passivity would 

 have set in. 



This retrogression of the potential lias been graphically represented 

 , , in figure 13 for chromium that 



had been activated in molten/ 

 KCl -f NaCl. The lower line 

 gives the potential as function 

 of the time, when the current 

 is raised from 0.2 to 0.5 mA, 

 the upper line when the current 

 is raised from 1.0 to 2.0 mA. 



*'T^ in minutes. ^ T|,e influence of the slow 



^° increase of the strength of the 



^'S* current was still more apparent 



for a piece of chromium that had been activated in ZnCl,. This 

 resisted a strength of current of 14 mA, when the current was 

 increased by 1 mA every three minutes. After interruption of the 

 current this electrode was more active than before the polarisation. 

 When after this the current was at once brought to 5 mA, the 

 electrode became passive ^). 



Another electrode was likewise activated in molten ZnClj. The 

 potential was — 0.542 in saturated KCl. The electrode was anodi- 



-o.s- 



M The influence of the interruption or enfeebling of the polarizing current 

 appears in a very peculiar way from the following experiment. A piece of chro- 

 mium, which was anodically polarized with 7 mA. in KGl-solution, was brought 

 in contact with a piece of zinc. This caused the potential to fall from — 0.538 to 

 — 0.750. Then the current passed into the solution chiefly through the zinc, which 

 caused the density of the cuirent, with which the chromium was polarized, to 



