880 
the ascending branch of (Z,) and in fig. 6 on the returning branch 
of curve (Z) and on the descending branch of curve (Z,). 
As we have found now the /,7-diagrams, we may easily deduce 
the corresponding concentration-diagrams with the aid of those. 
I shall not enter into this subjeet any further and leave this 
deduction to the reader. 
Leiden, Inorg. Chem. Lab. (To be continued.) 
Chemistry. — “A New Method for the Passification of Iron.” 
By Prof. A. Smits and C. A. LoBry pr Bruyn. (Communicated 
by Prof. P. Zeeman). 
(Communicated in the meeting of Dec. 21, 1916). 
I. If iron is immersed in an electrolyte, we have to deal with 
the following complex equilibria: 
Fes = Fes” — 2 As 
from which follows: 
ee a ee Ye 
Poa Bo a 
Fe, 2 Fe," + 61 
Those of these equilibria that are indicated by vertical arrows 
except the equilibrium between the uncharged ironatoms in the 
solid phase and the electrolyte refer to that part of the heterogeneous 
equilibrium that governs the potential difference. 
Now it has been pointed out before that the iron, which is in 
internal equilibrium, can be in electromotive equilibrium only with | 
a solution which contains almost exclusively ferro-ions, so that under 
these circumstances the equilibrium: 
Fer 2 Fe, -- OL 
in solution lies almost entirely to the left. 
If we now add ferri-ions, a consequence of this will be that+ 
ferro-ions and electrons from the iron go into solution, which disturbs 
the equilibrium in the iron surface. 
This disturbance can now cease again, as a result of the reaction 
Fes == Fes + 2 As 
