1485 
Chemistry. — “The Application of the Theory of Allotropy to 
Electromotive Equilibria’ IV. By Prof. A. Smits and Dr. 
A. H.W. Aven. (Communicated by Prof. J. D. vaN DER WAALS). 
(Communicated in the meeting of Feb. 26, 1916). 
1. Introduction. 
In some foregoing papers’) it bas already been demonstrated that 
the pbenomenon of passivity can be explained in a simple way by 
the application of the theory of allotropy to the electromotive equi- 
librium metal-electroly te. 
According to this theory the metal is complex, and with this 
complexity many different cases can present themselves. It is possible 
that the complexity only consists in this that in the metal we have 
to do with an tonisation-equilibrium of the metal, expressed e.g. by 
the equation : 
Me Meee ne ee 
It is, however, also possible, and this will occur in the metals 
of which ions are known with different valency, that there exist 
side by side more such ionisation equilibria, and that just as many 
as there are differently charged metal ions. 
lf of the metal JW there exist the ions MW and Jf, the two 
following ionisation equilibria will occur in the metal: 
MEM" +26 | 
and MM" +30 | 
It has further been pointed out that it is possible that the metal 
contains different kinds of ions, which have the same charge per 
atom, but which differ in size, as e.g. the ions M- and MM. 
bo 
In this case the metal is still more complicated, because then we 
must assume the following ionisation and dissociation equilibria: 
MAM" +280 
MEM SO oo es ee ee 
MM 
Before we examine more closely the phenomena of polarisation 
and passivity it is desirable to show to what new points of view 
the assumption of an ionisation equilibrium in a metal leads. 
We shall begin with showing this for the simplest case, indicated 
by equation (1), and not until the conclusions to which this case 
1) These Proc. XVI, p. 191; XVI, p. 699; XVII, p. 37. 
