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time solid /” + F”’ is deposited. In order to obtain the equilibrium 
FAP A4 FH G, consequently we have only to bring a sufficient 
quantity of / into a space. We have, therefore, again a congruent 
sublimation. 
D. The vapour G@ is represented by a point, which is situated 
with two of the solid substances on a straight line. We shall refer 
to this later. 
When we change the temperature, then also the sublimation- 
pressure of F+ F’ + F’’ changes, consequently in a P,T-diagram 
a sublimationcurve of + F’ + [’’ may be drawn. Herein the 
sublimationeurve of #4 /” + F”’’ is situated higher than that of 
FF, F+F” and F+ FH", that of F+ FH” higher than that 
of F and F’, that of F4 /’’ higher than that of # and /”’ and 
that of #” + F’ higher than that of /” and #7’. Of these seven 
curves, several may represent metastable conditions. To each of 
these sublimationeurves applies: 
„raw 
dT NN (8) 
Herein AW is the heat, which must be added, AJ” the change 
of volume, when a reaction occurs under a constant P and at a 
constant 7’ between the phases, which are in equilibrium. When 
the gas-laws are valid (8) can also be written in another form. 
We can represent the sublimationcurve of £+ 4” + F”’ also in 
the concentration-diagram. At change of 7’ we change viz. not only 
the sublimationpressure, but also the composition of the vapour G 
(point w). The point w consequently traces a curve in the concentra- 
tion diagram, the sublimationcurve of /’-+ /” + F’’. With each 
point of this curve a definite 7’ and P correspond. 
When this curye intersects one of the sides (or its prolongation) 
of the threephase-triangle FF’, the transitioncase mentioned sub D 
occurs. We assume that this point of intersection w is situated on the 
line FF’. Consequently a definite temperature 7’, and a definite pressnre 
P, belong to this point w. When we imagine the vapoursaturation- 
curves of F, F’ and F’’ to be drawn, it is apparent that those of / 
and /” touch one another in the point w. Consequently the pressure 
P. is the congruent or incongruent sublimation-pressure of / + #” 
belonging to the temperature 7. In the P,7-diagram the sublimation- 
curves of F4 PF’ + F” and F4 F’ will therefore, touch one _ 
another at the temperature 7. Consequently we find: when in the 
concentration-diagram the sublimationcurve of F+ 4” + f’” inter- 
sects the line /’/’, then in the P,7-diagram the sublimationcurves 
of Ftd’ + F'' and F4 F” touch one another in the P,7-diagram, 
