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not in equilibrium with each other; in facet various means are 
employed to prevent them from forming a homogeneous mixture. 
The following contains a new effort to study the galvanic cell 
from the point of view of phase rule. 
Those cells have been considered, which consist of a combination 
of 2 metallic electrodes, each surrounded by an electrolyte, containing 
the cation of the metal and connected with each other either directly 
or by means of an electrolyte. 
Equilibrium may exist between both the electrodes and the sur- 
rounding electrolyte and when that equilibrium is reached, there 
exists at the plane of separation a certain potential difference, which 
is the measure of the energy required to transfer an equivalent of 
the metal from the one phase into the other. 
Bancrorr is therefore in error in regarding the E.F. as an in- 
dependent variable, as a further condition of equilibrium. He says: 
“In addition to the ordinary conditions of equilibrium there is also 
the electromotive force.” 
The variables would then be the 7 components, temperature, pressure 
and the potential difference and from this it would follow that for 
an invariant system » + 3 phases were required. 
This is not the case, for a is completely defined when 7» phases 
are present in a system of 7 components at a given temperature and 
pressure (for instance by the formula of Nernst when „==? or 3). 
There exists, however, no equilibrium between the two electrolytes 
in the cell. They will tend to form a homogeneous mixture in 
which ease the composition is changed and the equilibrium with the 
electrode disturbed. 
Therefore, there can be no question of a real equilibrium in the 
whole of the cell so long as both electrodes cannot be in equilibrium 
with the same electrolyte and the EMF becomes zero. An apparent 
equilibrium may, however, be got by preventing as much as possible 
the diffusion of the two electrolytes. 
Considering the cell as a combination of two systems consisting 
of metal and electrolyte, the equilibrium of the separate systems should 
be diseussed before alluding to that existing in the cell. 
The equilibrium between the metallic electrode and the surrounding 
electrolyte and the potential difference at their plane of separation. 
A. The electrode consists of a single metal and the surrounding 
electrolyte also contains cations of that metal alone. 
When the electrolyte is a fused salt of the metal, we have a system 
of 2 components in 2 phases which at a given temperature and press- 
