144 



Besides, the diffusion layer becoiTies thicker again, as the metal no 

 longer dissolves; the point B', therefore, gets in B". C" must 

 lie higher than (', because at C" more hydrogen diffnses towards 

 the boundary surface than at C on account of the slight thickness 

 of the diffusion layer. This hydrogen must also pass into (he liquid 

 more rapidly, which is only possible when i^^' C" is greater than 7^' 6'. 



When the value 6" has been reached, the hydrogen charge at 

 the boundary surface will decrease again through the continual 

 passing of hydrogen into the liquid, and through the supply of hydrogen 

 from the metal going more slowly, because the diffusion layer 

 becomes thicker. At last a stationary state is again reached, which 

 is equal to the state before the polarization, and in which the 

 hydrogen charge of the boundary surface is F' 6"", the concentration 

 of the hydrogen in the diffusion layer B'" C". 



The greater the density of the current, the smaller will be F' C', 

 the thinner will be the diffusion layer, and the higher therefore 



will C" lie. 



Hence the following particulars will be observed for the potential 

 of electrolytic chromium. When electrolytic chromium with a fresh 

 surface is brought into an electrolyte, the hydrogen charge at the 

 boundary surface is great, F(r, and the potential strongly negative. 

 When this chromium is left in contact with the liquid for a long 

 time, the boundary surface of the metal loses part of its hydrogen, 

 the hydrogen charge falls to FC, and the potential becomes more 

 positive. When we polarize anodically, the hydi-ogen charge decreases 

 to F' C', the potential becomes, therefore, still n)ore positive. When 

 the current is now interrupted, then the hydrogen charge rises to 

 F' C", the potential becomes much more negative, but gradually the 

 hydrogen charge decreases again to F' C", and the potential rises 

 to the value that it showed before the polarization. 



This course is quite in concordance with what was drawn in 

 figure 7 of the second communication. 



Accordingly tlie potential reaches a minimum which is the deeper 

 as C" lies higher, hence as the strength of the current is greater 

 and consequently the diffusion layer is thinner. 



When the strength of the current is very small, and the diffusion 

 layer is thick, it may occur that C" does not get above C"", and 

 that the potential does not pass through a minimum, as is the case 

 with the line for 1mA in figure 7 of the second communication. 



It is clear that the phenomena for anodic polarization will, 

 therefore, chiefly be determined by the hydrogen content of the metal. 



These phenomena being different for chromium on copper, on 



