(455 ) 
be drawn at the third locus, parallel to the V-axis, represents a point 
‘for which two values of v, making 
z = 0, have coincided, and 
might therefore be considered as critical point of the mixture, when 
it behaved as a simple substance. 
Let us now examine the course of the isobar, passing through 
B and B. On the left side of B it must indicate volumes smaller 
than that of the connodal curve, because the pressure ot B is greater 
than that of A. In D it is supposed to pass through the minimum 
pressure of the mixture, whose #=ap. That this will take place 
on the right side of B agrees again with the fact that the pressure 
on the connodal curve increases from A to P. In D the isobar under 
consideration must have an element in common with the isothermal 
of the concentration zp and from that pointit will go back to smaller 
concentrations. It is supposed to meet in D' for the second time the locus 
d, ‘ 
going through the points for which - = 0; viz. the branch where the 
av 
pressure on the isothermal is maximum. So the point D' must lie 
on the left side of B, From J’ the isobar moves on to greater 
values of z. 
At the chosen value of p therefore, there is a continuous series 
of phases of the binary mixture. They are liquid phases on the 
left side of B, gas phases on the right side of B. Between B and D the 
isobar cuts the spinodal curve, also between D' and B, If we indicate 
these points of intersection by E and L’, the metastable phases are 
to be found between B and ZE. In the same way between £' and B'; 
whereas all the phases between Z and £’ are unstable. 
A line parallel to the volume axis and for which rp' <#<zp, 
cuts the isobar in three points. For all these values of # there are 
therefore three different phases which have the chosen value of pas 
pressure, and therefore £ will have three values. For all values of 
« outside zp and zp' there is only one volume that has p as pressure, 
and therefore ¢ will have one value. It is viz. easy to see that no 
other points than those marked can have p as pressure. 
So if we have to draw { as function of # at this pressure and at 
this temperature, we get fig. (3). To conclude to this form, we have 
to take into account: 1st that 2 at«=0 is equal to — o and for 
s=l to +, which follows from the pure function of z, From 
+... 2nd that in the stable 
30* 
. . de ry. © 
this we derive viz) — = MRT log 7 
dtpt } 
