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ad and a'd. On both curves a point with a maximum pressure 
and one with a minimum temperature is supposed to occur. 
Besides the regions whose limitations we know now we find at 
the right of curve a'd' also the regions 1+ G, L and G which, 
however, are not drawn in the figure. 
In order to survey the connection of these regions we might 
draw a representation in space; for this we imagine the composition 
of the complex F+ F’ to be placed perpendicularly to fig. 1. 
Instead of the spacial representation itself we will here consider its 
sections with planes. 
If we place a plane perpendicularly to the concentration-axis we 
get a P,7-diagram which applies to a definite complex, if we place a 
plane perpendicularly to the Z-axis we get a pressure-concertration 
diagram which applies to a definite temperature, and if we place 
a plane perpendicularly to the P-axis we get a temperature con- 
centration diagram which applies to a definite pressure. 
Let us place first a plane, which intersects the three sublimation 
curves, perpendicularly to the Z-axis; we then obtain a section as 
in fig. 2 in which # and F” represent the two compounds F'and #’. 
Perpendicularly to this line FF’ is placed the P-axis. 
In order to be able to indicate readily the different regions occurring 
in this and the following diagrams we will represent: 
The liquidum region by JZ, the vapour region by G, the solid 
region by + FI’, the region F+G by 1, F’ + G by 2, FHL 
by 8, FHL by 4, Ltr by 5, F+L4+G by 6 and #’+L+G by 7. 
If in fig. 1 we suppose a straight line, which intersects the three 
sublimation curves, to be drawn parallel to the P-axis, we notice 
that in fig. 2 the regions F+ F’,1=F+4G, 2—/"4+G and 
the region G must appear. The points s, s and s” represent the 
sublimation pressures of the solid substances /’ and /” and of their 
complex P+ #F”; the complex, therefore, has a higher sublimation 
pressure than each of its components by itself. 
The curve ss" represents the vapours which 
can be in equilibrium with solid /, curve 
ss" those which can be in equilibrium with 
solid #”; these curves have in s and s a 
horizontal tangent. 
We now take a complex P+ F” of the 
composition c, so that the complex itself is 
represented by a point of the line cc’. As this 
line intersects the regions #’+ F’, 2 and G, 
then according to the pressure chosen, there 
