147 



in tlie duration of the phenomenon may be atlribntecl to a diffeieiioe 

 in the hydrogen content of electrolytic chromium and Goi,d|[;HiMIüt 

 chromium. The former can bear a much stronger current already 

 at the beginning- of the anodic polarization than the latter. In 

 consequence of this the displacement of the boundary surface GF 

 to (m" F" goes much more quickly for electrolytic chromium than 

 for chromium of Goldschmidt, hence also the activation on anodic 

 polarization proceeds more quickly for electrolytic chromium. 



As has been described in the second paper, a piece of Goldschmidt 

 chromium that has become active through anodic jwlarization, can 

 not bear the same strength of current any more when the current 

 has been broken for some time, though the potential is then much 

 more negative than immediately after polarisation. This, too, can be 

 accounted for by the diffusion of the hydrogen in the metal. Before 

 the polarization the concentration of the hydrogen in the diffusion 

 layer is represented by BC in figure 4. When the electrode is 



anodically polarized, and the strength of the current is slowly carried 

 up, a stationary state will be reached after some time, for which 

 the concentration of the iiy drogen in the diffusion layer, which has 

 now become a good deal thinner, is represented by B^^C^. When 

 the current is interrupted, the hydrogen concentration at the boundary 

 surface rises in consequence of the great gradient of concentration. 

 Besides the thickness of the diffusion layer increases, which extends 

 inwards in the metal, and is no longer dissolved from outside. The 

 course of the concentration of the hydrogen in the diffusion layer 

 is now successively represented by B^(\, B^C,, B,C,, B^C\, Bf^C\, 

 and 7i«6V With B^C^ the concentration of the hydrogen at the 

 boundary surface is greatest, the jK>tentiaI, therefore, most negative. 



10* 



