( 184 ) 
ure is completely defined. If the electrolyte is a solution of a salt of 
the metal, there will be 3 components and, therefore, the concentration 
must also be given. The potential difference is determined by the for- 
’ RGP 
mula of Nernst: ar =—l— in which P=the solution tension of 
nh P 
the metal, p= the osmotic pressure of the cation and n= the 
valeney of the metal. 
B. The electrolyte consists of two different metallic salts M,Z and 
M,Z and in the electrode both metals of these salts may be present. 
Assuming that the electrolyte forms one homogeneous phase, the 
following distinction may be made in the equilibria of the electrode 
and electrolyte. 
I. At the given temperature there is no reaction between the two metals; 
they form therefore neither a compound nor a liquid or solid 
solution. 
Starting from the electrolyte, containing only the salt M,Z (fused 
or in solution), there is a series of electrolytes with an increasing 
amount of J/,Z, which ean only be in equilibrium with J/,, and 
another series, starting from J/,7 with increasing quantities of JZ, Z, 
which are only in equilibrium with J/,. 
Where these two series meet, we have an electrolyte, which is 
in equilibrium with both JM, and J/,. When there is no solvent 
and we are consequently dealing with a fused salt mixture, there 
is only one electrolyte which satisfies this equilibrium. We then 
have 38 phases: electrolyte, JM, and J/, and 3 components M,, M, 
and the acid group Z. The equilibrium at a given ¢ and p is, there- 
fore, completely defined. 
If, however, a solvent, and consequentiy a fourth component is 
also present, then, according to the quantity of this solvent, there will 
be a series of electrolytes which satisfy the conditions of equilibrium. 
To follow the change in the potential difference, we may imagine, 
that a part of the ions J/, in the electrolyte containing J/,Z, has 
been replaced by J/,, but in such a way, that the total concentra- 
tion of the ions J/, + J/, remains constant. The potential difference 
between Ms and the electrolyte will increase, because in the equation 
x, = — ‘| —, p, becomes smaller and consequently 2, becomes greater. 
The same ae to z,, the potential difference between the metal 
AM, and an electrolyte containing only JZ, cations, when part of these 
ions is replaced by ions J/,. 
