683 



of this. If a metal really contains different kinds of ions they will, 

 as was stated before, differ in reactive power; hence an attack may 

 result in a change of the concentration in the metal surface, in the 

 sense of enobling. It is, however, to be seen hefoi-ehand that tlie 

 investigation in this direction will be successful only when the in- 

 ternal equilibrium in the metal surface in contact with the electro- 

 lyte is established slowly enough. If this equilibrium is established 

 with very great velocity, no disturbance will of coui-se, take place, 

 even though the ion-kinds differ greatly in reactivity. 



It appeared in our previous investigation about polarisation that 

 the metals Ag, Ca, Ph are exceedingly little polarisable, from which 

 we inferred that these metals quickly assume internal equilibrium. 

 Hence the etching of these metals promised little success. Quite in 

 agreement with our anticipations it appeared that the potential dif- 

 ference metal- Vj^ norm, salt solution was not to be changed 

 for these metals by previous etching. 



To examine this the electrode of the metal that w^as to be investi- 

 gated, fastened to a platinum thread was etched with acid, and then 

 quickly rinsed with water. Then this electrode was immerged in 

 a Vio norm, salt solution, and made to rotate, after which the 

 potential with respect to a Vio N. calomel-electrode was measured 

 as quickly as possible. 



When the above mentioned metals according to our anticipations 

 had yielded a negative result, the metals Co, JSfi, Cr, and Fe were 

 examined with the following result: 



