( 544 ) 
The accurate knowledge of the course of the isobars is required 
for indicating the value of ¢ at every value of p for the binary 
mixture and so also for the description of the shape of the ¢-surface 
for a ternary mixture, if the here discussed peculiarity occurs for 
at least one of the pairs. And in order to be able to do this also 
at higher temperatures, at which the critical phenomena occur, and 
because the course of the isobars at such temperatures is greatly 
modified, 1 have represented this modification in Fig.8 (pag. 543). 
The principal modification, which is to be introduced in fig. 7, 
and which leads to fig. 8 is this, that the isobar through P presents 
its whole closed curve within the limits of <=0 and =1. The 
curve PQ has slightly changed its place and its shape (see Cont. 
II pag. 88), but the change is comparatively small. That the whole 
curve keeps within the zv-diagram follows from two circumstances. 
Ist. The pressure of P, which is a minimum pressure on the iso- 
thermal of zp, lies but little below that which can be realised as 
liquid phasis, if the temperature is close to that at which both 
minimum- and maximum pressure disappear and 2"¢ the difference 
of pressure along a connodal curve generally increases at higher 
temperatures. The whole curve showing itself, the course of isobars 
for which p < pp can also take place without interruption within 
the whole ev-diagram — at least for values of p lying above a 
certain limit which may be derived from the preceding conside- 
rations without nearer indication. If we follow such an isobar, e.g. 
CFHIMNO, it must be possible to draw a tangent parallel to the 
v-axis in F and H and also in M and N, in which four points the 
Rae ; 
eurve for which 5) = 0 js cut; in point J, in which the curve for 
Uae 
Legs : ; 
which (2) = 0, is cut, the tangent must be parallel to the z-axis 
dz” » 
Between F and H, and also between M and N the value of z 
retrogrades. For the isobar passing through & the retrogression on 
the left side of the figure continues, but it has just ceased on the 
right side. 
In fig. 8 point S indicates the plaitpoint and the isobar passing 
through S must therefore touch the connodal curve in that point. 
In the same way the connodal curve must touch a curve of equal 
pressure in the points D and D'. All this proves that the tempe- 
rature is thought to be so high, that there is still question of a 
maximum pressure on the connodal curve. (Consult the observations 
of KueNEN and those of Quint for mixtures which have minimum- 
critical temperature). Between S and R is retrograde condensation 
