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liquid points of the unary system lie at another concentration, so 
that in the P,T,X-spacial figure of the unary system the equilibrium 
between liquid and vapour is indicated by two lines, the coexisting 
points of which differ in x-values, and the same of course also 
applies to every other two phase equilibrium in the unary system. 
It is clear that the P.T.-projection just hides what is characteristic 
in the unary system, because in this projection the difference in 
concentration of the coexisting phases cannot find expression, and 
every pair of lines for two-phase coexistences projects itself as one 
line in this representation. 
It is my purpose to discuss here some P,X-sections of the pseudo- 
binary P,T,X-spacial representation, and to point out the place of 
the unary system there. 
To be able, however, to determine the place of these sections it 
is not necessary to draw the spacial representation ; the P,T-projection 
will suffice, and this is the reason that I will now proceed to a short 
discussion of this projection. 
Beforehand it must be stated that two cases should be distinguished. 
First the case that the pseudo-components @ and 3 are isomers, and 
secondly the case that 8 is a polymer of «. 
In the first case the P,T,X-spacial figure can possess a eutectic 
line, whereas as | showed already before, in the second case a 
eutectic line will not occur as a rule. 
8. The P,T-projection of the P,T,X-spacial figure of the pseudo- 
binary and of the unary system for the case a and 8 are isomers. 
We shall now proceed to a short discussion of the P,T-projection. 
The thin continuous lines in Fig. 1 are the three-phase lines of the 
pseudo-binary system and the two-phase lines of the pseudo-compo- 
nents, the thick continuous lines referring to the two-phase lines of 
the pseudo-components, the thick continuous lines referring to the 
two-phase lines of the unary system. For the greater clearness the 
phases of the unary system are denoted by Sy, Lu, Gu. (See Fig. 1 
following page). 
At the point where the vapour-tension line of the unary system 
KuD, more closely defined by Lu + G,, meets the three phase line 
Say Lb +G, the unary point of solidification wrder the vapour 
pressure is reached. This takes place at D; then two new lines of 
internal equilibrium of the unary system appear in this triplepoint : 
the meltingpoint line DE, more closely indicated by S,, + Ly, and 
the line of sublimation DA’, where Su, + Gy coexist. In the point 
