1134 



5. Previous catliodic polarisation makes the anodic current 

 strength which this chromium can resist without becoming passive, 

 smaller. 



6. The increase of the activity on continued anodic polarisation 

 is caused by a change in the metal surface. 



7. Cfiromium of Goldschmidt that has become passive through 

 anodic polarisation in a solution of KCl, becomes active on heating 

 of the solution, also during the passage of the current. On cooling 

 the activity remains preserved, at least if the current is not too strong. 



When the chromium cools down in the solution without becoming 

 anodically polarized, the activity which it retains after cooling, is 

 smaller than when the current continues to pass on cooling. 



In the literature a few more examples are found of the activation 

 through the anodic polarisation observed here. Thus Pelade ^) states 

 that a nickel electrode as negative pole of an element, the positive 

 pole of which was platinum in chromic acid, gave a stronger 

 current (hence was more negative) when it had first been strongly 

 anodically polarised. 



The same thing was found by Rathert '). A nickel electrode which 

 in NiSO^ presented a potential of -|- 0,237 V, had a potential of 

 — 0,125 V after anodic polarisation, of -|- 0,64 V after catliodic 

 polarisation. He attributes this phenomenon to changes in the con- 

 centration in the liquid. That for chromium such an explanation 

 is not valid, has already been demonstrated above. 



In the following paper we shall endeavour to give an explana- 

 tion of the above described phenomena. 



Chemical Laboratory of the Ihiiversity. 

 Aiiuterdam, January 1918. 



1) Zeitschr. f. physik. Chemie 76, 513, (1911). 

 3) Zeitschr. f. physik. Chemie 86, 567, (1914). 



