563 



0,058, {Ms')acth 



^Mactii'e -L — ^M j>assiire-L = l'Og 



yM g fpasaire 



For the Volta-effect holds the relation: 



Am,-m^ = ~ 



from wliich follows in Ihe same wa}^ as we have derived this for 

 the potential difference metal-liquid, that the following equation holds 

 for the Volta-effect -. 



A.ü._j;, = 0,058 log —^-^ 



SO that : 



^Mxactive-Mi — ^ Mipnssi,^e—Mi == 0,058 % ƒ ' " — -- 



\y M\)passive 



When we call 



then also 



(■'"IS /active 

 V-"*is ) passive 



{C'M^jnciive 



\'^ M\}passire 



It follows from this that when on polarisation or passivation Ihe 

 change of the potential difference metal-electroljte is: 



0,058 

 log n 



V 



that of the Volta-effect amounts to : 



0,058 log n 

 hence v times the value. 



What we measure is the sum of these two changes: 



r + 1 



V 



0,058 %r^ 



V 



Hence the part of this total change is due to the Volta- 



^ V + 1 



effect. This is, therefore, \ for a uni-valent metal, and f for a bi- 

 valent one etc. 



When it is now borne in mind that on passivation through anodic 

 solution the potential difference metal-electrolvte, as it is found by 

 measurement, can change by an amount of 1 or 2 Volt. (e.g. 1.7 

 Volt, is found for iron), it follows from this (hat according to these 

 considerations also the V^olta-effect is subjected to a great change ^). 



1) It must slill be pointed out that the case iron is certainly more intricate than 

 the case considered above, because iron contains ions of different valency. 



37 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



