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temperature is consequently the sublimationpressure of #7. Therefore 
we find: r can coincide with /”; the equilibrium /-+ #”+G 
passes then into /’+ /”-+ vapour /”. This can only be the case at 
a definite temperature and under a corresponding pressure; this 
pressure is the sublimation-pressure of /”. 
In the P,T-diagram the sublimation-curves of / + F” and of F” 
have, therefore, a point in common with one another, as the first 
curve is situated generally above the second, the two curves touch 
consequently one another in this point. We may express this also 
in the following way: when in the concentrationdiagram the com- 
mon point of contact of two vapoursaturationcurves goes through 
F’, then in the P,7-diagram the sublimationcurves of /’-+- F’ and 4’ 
touch one another. 
This point of contact divides both the curves into two parts. At 
the one side of this point on the curve of + #’ congruent subli- 
mation takes place and the curve of /” is stable; at the other 
side of this point on the curve of /’+ #” incongruent sublimation 
takes place and the curve of /” is metastable. 
2. # and F” contain together two components only. 
The line FF’ coincides, therefore, with one side of the triangle. 
This is always the case when both the substances are components ; 
it may yet also be the case when one of them or both substances 
are binary compounds. The previous considerations sub IV. 1. apply 
still also now, with slight changes however, which- we shall indicate 
briefly. Firstly we take (at 7’ constant) a pressure, under which 
the two vapoursaturationcurves intersect one another. The two curves 
have, however, one point of intersection now, so that only one 
equilibrium /’+ /” + G occurs. When we assume, for fixing the 
ideas, that # and /” contain together the components B and C, 
this point of intersection moves on decrease of pressure towards the 
side BC, in order to fall on the side BC under a definite pressure 
P,. As r is now a binary vapour, the equilibrium +4 FF’ + G, is 
binary; P, is the sublimationpressure of #° + /”. 
Although 4, /” and r are situated on a straight line, yet the 
two curves do not touch one another in this point 7 in this case; 
this is, as we have seen above, indeed the case when 7 is situated 
within the triangle. The cases 4, B and C of IV.1. apply to the 
position of the points /, ZF’ and r with respect to one another. 
On further decrease of pressure the two curves contract, the 
same as is described in [V.1 applies to their position with respect 
to one another, the considerations given there about the sublimation- 
curves remain also valid here. | 
