( 454 ) 
we seek the relation of the three values of ¢ for a binary mixture. 
As it is our purpose to examine how the three curves unite toa 
single curve, we shall assume values of p and T, at which the quan- 
tity £ has three values for certain values of #, whereas it has only 
one value for other values of «. Let in fig. 2 the curve ABPB'A' 
represent the connodal curve of the binary mixture in an zv diagram. 
It is assumed in the figure that for « > zr at the given value of 
T no separation into two phases can occur, however great the value 
of p be. The point & represents therefore the critical point of con- 
tact, and P the plaitpoint. Going from 4 to P and also from A to 
P, the pressure of the coexisting phases of the binary mixture 
increases. Hence for xr > # > ep there is retrograde condensation 
of the first kind. Let B and B' represent a pair of nodes, for which 
«B > eg. Then it must be possible to draw an isobar passing through 
B and B', because at coexistence the pressure must be the same. 
Besides the connodal curve, we have also drawn the curve CPC, 
which indicates the limit between the stable and unstable homoge- 
EA 
ALT de dv 925 
de? ti(ié 2p 
neous phases. For the points of this line 
is equal to 0. I may assume as being known that for a binary 
system this curve coincides for z=0 with the point for which 
op 
of the first component is equal to 0. 
Ü 
ee dp omy 
In the third place the locus of the points for which eo 
Vv v 
is equal to 0, is given. This locus lies entirely within the 
dw 
region of the unstable phases. For the spinodai curve viz. a2 
. vu 
dw Be dw 
and .— must both be positive and their product must be {—— | - 
dv? dede 
dw dp Jt d 
From —- = — positive, follows negative, hence the points 
dv? dv dv 
; : c dp ; 
of the spinodal curve lie outside those for which = = 0, Only 
av 
special cases the spinodal curve and the locus CAC" will have points 
in common, viz, for #=0O or «= 1, or for the special point for 
dw Ck 
IN 
Ordo 
be disregarded for the present. The point A, where a tangent might 
which ) is equal to 0. The last mentioned case will 
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