Chemistry. — "■(Jii the Phenomenon of Anodic Polarisation.'' II. 

 P)y Prof. A Smits. (Con)mnnicated by Prof. P. Zekm.vn). 



(Communicated in the meeting of March 29, 1919). 



1. Ill this cominmiicatioM will be discussed the peciibar pheiio- 

 meuoii that was mentioned in the tirsl comniuiiication witli the above 

 title. As was already staled there 1 observed the described pheno- 

 menon for the first time with Mr. Lobry im Hkuyn for iron and 

 nickel more than two years ago, but I did not publisii it, because 

 1 thought it necessary to study the phenomenon (irst more closely. 



Afterwards the same phenomenon was found by Mr. Atkn ') for 

 chromium, but most probably he has not interpreted it correctly. 



Explanation of the Phenomenon. 



2. It has appeared from tiie preceding communication thai the 

 "phenomenon" appeared for iron when this was polarized anodicaliy 

 in a solution of ferro-sulphate or ferro-chloride, which had, indeed, 

 been freshly prepared, but had not beforehand been heated with 

 iron-powder. 



We have already pointed out before that iron in the state of 

 internal equilibrium can oidy coexist with a solution which practi- 

 cally possessed no ferri-ions. It is further known that a solution in 

 which ferri-ions occur, clearly disturbs iron, and the more strongly 

 as the ferri-ion-concentralion is greater. As we communicated already 

 before we have even succeeded in making iron passive by simply 

 immersing it in a concentrated solution of ferri-nitrate. 



Hence (he potential of the iron is less negative in a solution that 

 contains ferri-ions than in a solution that coexists with unary iron, 

 which latter solution is practically free from ferri-ions. In the solution 

 with which the "phenomenon" was obtained the ii'on accordingly 

 did not present the polenlial of internal equilibrium, bnt the potential 

 was less negative. 



When now iron in such a liquid is anodicaliy brought to solution, 

 the electrolyte will undergo a change in the neighbourhood of the 

 iron, because iron when it is not passive, certainly goes into solution 

 pi-actically e.vclusively as ferro-ion. The iron is disturbed during this 

 anodic, dissolving, as appears from the less negative potential of the 

 iron during the passage of the current, and at the same time the 

 iron gets surrounded by a liquid layer that is poorer in ferri-ions 



1) These Proc XX, p. 1121. 



