1004 
which is, however, no more transformable now. This equilibrium 
(M) is represented in fig. 1 (VIII) by the line GeZ,= GLZ, the 
turning-line of the region Z,LG, the stable part of which is situated 
between the curves LO and Lc. According to the position of the 
curves La, Lb and Le with respect to the line GLZ, in the P,7- 
diagram of fig. 2(VIII) different cases foliow which are in accordance 
with the figs. 3-—9. 
At the deduction of the figs. 1—5 we have assumed the following. 
When we bring the equilibria (M), (/,) and (/7,41) from 7; and P, 
to the temperature 7’, and corresponding pressures, then the variable 
phases (e.g. #-) get other compositions in each of the three equili- 
bria [e.g. Fr, Fr and F,'"|. This is however not always the case. 
Let us assume viz. that in the invariant point the phases of the 
singular equilibrium : 
(M=F, + EH... + Fret... + Fite 
contain together only n—1 of the components, in the equilibrium (J/) 
then one of the components is missing; we call this component X. 
The variable phase / contains, therefore, also only n—1 compo- 
nents (or less) and this is not only the case at 7’, and under P,, but 
also at other 7’ and P; this is not only the case in the equilibrium 
(7), but also in the other equilibria. 
This is e.g. the case when #, is a gas and K a substance which 
is not volatile or when #, is a mixed-crystal and A not miscible 
with this. 
In the equilibrium: 
CF, FS) =F, ie ee 
we have now n-—1 components in 7 phases, consequently it is not 
bivariant, but monovariant; in the P,7-diagram it is, therefore, not 
represented by a region, but by a curve. The equilibria (M), (P,) 
and (F,) coincide, therefore, with this curve. As the equilibrium (J/) 
of course is not transformable (viz. the substance A is missing), the 
(M)-curve is bidirectionable and the curves (/,) and (/’,) coincide, 
therefore, in opposite direction. Then we obtain fig. 2X). A similar 
case shall occur e.g. in a ternary system with the components 4, B 
and C, when in the invariant point exists the equilibrium 
AtB+C+4+L1+6 
in which the gas-phase G contains only two substances e.g. Band C. 
Summary of the P,T-diagramtypes. 
When we take an invariant point with the phases /,... Eno, 
then different cases may occur. 
