( 189 ) 
coincide to the right and the left with the a-axis, that is when the 
metals do not mix. 
An example of the case of fig. 4 is found in my investigation *) 
of the equilibrium between fused lead, zinc and their chiorides. At 
elo we yu 100 9), nok ed Ob ns 1) == IA OF Zn, 3-5/5 :0F PD 
H= 99,9 °/, of ZnCl,, 0,1 °/, of PbCl, and if 74 is taken as 0 then 
Korp — 0,277. Volt and. wp = 0,288. Volt. 
A second example is found in the cadmium amalgams, investigated 
by Janerr*) and Bun’). Further researches are those of Mrynr and 
RrcHarps and Lewis on the dilute amalgams, those of LiyprcK *) and 
those of HerscHkowitscH®), who met with the case represented by fig. 4 
in his investigation of Cd—Sn, Cd—Pb, Zn—Sn, Zn—Bi, Cu—Ag. 
In all these cases the concentration of the nobler metal in the 
electrolyte is very small; to a large extent the curve ALB almost 
coincides with J/, 2. 
I. The two metals form a compound. 
If the compound is present in a pure condition there will only 
be 2 phases and at least 3 components. Even without solvent the 
system is still monovariant at constant temperature and pressure. As 
in case I, if one of the pure metals forms the electrode, a series of 
solutions exists with varying proportions of the salts MZ and 
M,Z, which may be in equilibrium with this compound. The 
limit of this series is reached when the solutions are also in -equili- 
brium with a second metallic phase (one of the pure components, a 
liquid? or solid solution or a second compound). 
In order to make use of Nernsv’s formuia to calculate the potential 
difference, it is necessary to assume that the electrode forms ions of 
the same composition as the compound, for instance of AuAl,, Zn, Ag, 
etc. and to substitute the concentration of these ions in the formula. 
The solution pressure is then a definite constant for this compound, 
as it is for every pure metal: 
PO se 
1,2 
therefore ier Merc ES fede 
1) Z. f. anorg. Ch. 25 126. 
2) Wied. Ann. 65 106. 
5) Inang. Dissert., Amsterdam 1901. 
4) Wied. Ann. 35 311. 
5) Z. f. phys. Ch. 27 123. 
13 
Proceedings Royal Acad. Amsterdam. Vol. V. 
