( 194 ) 
Owing to the small rise of the line AG, the first case is sure to 
occur but rarely, as the line GHK then stands a chance of not being 
again intersected by AG and this case will pass into that of D (see below). 
H may be situated higher or lower than A. 
Fig. 6. If, in addition to the compound, two solid 
solutions are possible (J/, in which a little 
M, and MM, in which a little J/, is dissolved), 
the a-curve takes the course indicated in fig. 6, 
which differs from fig. 5 in this, that in presence 
of the electrolytes A to G pure M, is replaced 
by an electrode of varying composition, repre- 
sented by the line AC, and in presence of the 
electrolytes B to A metallic phases 6 to occur. | 
The line BF may either rise or fall ’). 
An example of this case is probably the system Hg, Ag, NO,, examined 
by Oge (Le.) for dilute solutions of Ag in He. 
b. If the compound cannot exist in presence of an electrolyte in 
which the ratio of the cations is the same 
as that of the atoms in the compound and if 
we consider the case in which in addition to 
the compound two solid solutions are possible, 
we get fig. 7. 
Metallic phases from A to C are in equili- 
brium with electrolytes from A to G. From 
C to D the electrode consists of a mixture 
of the two phases C (a solution of M, in M) 
and D (the compound). The potential difference 
is constant. 
As therefore, the compound is not in equilibrium with an electrolyte 
having the same ionic ratio, it will, in contact with such an electrolyte, 
dissolve with separation of J/,, and tend towards the equilibrium 
G, D, C. If, before attaining this, D has totally dissolved, a metallic 
phase on the line AC and an electrolyte on the line AG will remain. 
From D to MZ the pure compound is in equilibrium with an elec- 
trolyte of varying composition, situated on the line GA. The potential 
difference rises. The metallic phase /” and the compound / are in 
equilibrium with the electrolyte A. As long as these three are present, 
the potential difference is constant. If, however, the electrode reaches 
a composition to the right of /’, the compound will have disappeared 
1) In fig. 6 to read K instead of F and F instead of P. 
