1547 
diagram (fig. 2) this region is situated between the curves ic and 75 
and it extends over the curves (Cr) and (Z,). In fig. 4 this region 
is drawn once more with its limit-curves; the other curves have 
been omitted. 
Now we take a temperature 7, bigher than 7’, (fig. 1). When we 
take 7’.-— 7, then the saturation-curve under its own vapour- 
pressure of Z, is represented in the concentration-diagram (fig. 1) 
by eurve Dkk and in the P,7-diagram (fig. 4) by the line bk, 
parallel to the /-axis. It is apparent from fig. 1 that the pressure 
in the point / is higher than in 5, in fig. 4 / must, therefore, be 
situated higher than 5. When we take 7’. = 77 = T,, consequently 
the temperature of the invariant point, then the saturationcurve 
under its own vapourpressure of Z, is represented in fig. 1 by curve 
Lvq, in fig. + by the straight line vig. As it is apparent from fig. 1 
vw) 
ry, 
L 
7 
Fig. 4. 
that the pressure is higher in v than in point Z, in fig. 4 the 
point v must, therefore, be situated higher than 7. As this is valid 
for each temperature 7, higher than 7, the region Z,LG must 
have, therefore, a turning-line which is represented in fig. 4 by 
curve erh. 
Now we take a temperature 7, lower than 7, e.g. 7, = T.. In 
fig. 1 the saturation curve under its own vapourpressure is repre- 
sented by cu; hence it is apparent that the pressure decreases starting 
from c, so that in fig. 4 the point w must be situated below c. 
The bivariant region Z,LG has, therefore, quite another form 
above 7, than below 7. Below 7, it falls viz. starting from its 
