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a series of ternary and with two binary vapours. The one binary 
vapour contains B and C, the other B and A. The equilibrium is 
determined by (1) when we put herein «e= 0 and @='0.. The 
rules mentioned above, apply again to the movement of this curve 
on change of P or of 7. The same as in the case I applies to the 
disappearance of the vapoursaturationcurve in point B, to the subli- 
mation-pressure and to the sublimationcurve of B. 
IV. The equilibrium #4 /” HG; G is a ternary vapour. 
We distinguish herewith two cases, according as the solid sub- 
stances together contain the three components or not. 
1. F and F” contain together the three components. 
The line FF’ consequently is situated within the triangle; of 
course this is always the case, when one of the substances or both 
are ternary compounds. It may however be also the case when both 
substances are binary compounds and even when one of those is 
one of the components. 
The equilibrium /’-+ /” + G@ is, under a constant P and at a 
constant 7. invariant; this means that at a given temperature and 
under a given pressure the vapour has a fixed composition. We may 
understand this also in the following way. We imagine under the 
given P and at the given 7 the vapour saturationcurves of I’ and 
F’ to be drawn. These: may either intersect one another or not; 
they can touch one another as transition-case. When they do not 
intersect one another, no vapours exist; when they intersect one 
another, two vapours G, and G, exist, which may be in equilibrium 
with F4 F’, both these vapours are situated on the two sides of 
the line FF’. The points #,F’ and r may be situated with respect 
to one another in three ways. 
A. The point r is situated between / and /”; consequently the 
two curves touch one another outwardly in r. Consequently the 
reaction + F’ ZG may occur. When we bring / and /” into, 
a space, a part of each of these substances evaporates in order to 
form the vapour G. We eall this a congruent sublimation of / + 47. 
B. The point /” is situated between /’ and 7; both the curves 
touch one another in 7, consequently externally ; the vapoursatu- 
rationcurve of / surrounds that of /#”. Consequently the reaction 
Ff’ 2FAG may occur. When we bring / and £” into a space, 
then, in order to form the vapour G, only a part of /” shall eva- 
porate, while at the same time solid /’ is separated. In order to 
obtain the equilibrium 4 + /” + G, consequently we have only to 
