1394 
When in fig. 1 (II) the point X coincides with one of the phases, 
e.g. with phase 5, then this point can only represent this phase 5 
and nothing else, the tetravariant equilibrium 5 has to oecupy, 
therefore, all spaces in fig. 2 (II). The same applies of course also 
to each of the other regions 1, 2, 3, and 4. 
Considering the concentration-diagram of fig. 3 (ID) we see 
at once that each of the regions 1, 2, 3 and 5 has to occupy 
all spaces in the corresponding /,7:diagram. [We have to bear in 
mind that the figs. 4 (ID and 6 (II) kave to be changed mutually]. 
This is, however, not the case with the region 4. It is apparent 
from fig. 3 (ID into which equilibria the phase 4 can be divided, 
it follows from fig. 4 (II) in which order of succession those equi- 
libria will oeeur in a eyele of the phase 4. We find: 
1123-5 4) 125 > 8) 
Previously we have shown that with each property in a P,7- 
diagram a property in the concentration-diagramity pe corresponds. 
This appears a.o. also from the two following properties, which 
we have deduced in this communication, viz. 
The concentration-regions, which are represented by a point of a 
P,T-diagram, occupy the whole region in the concentration-diagram 
and they do not coincide completely nor partly ; 
the equilibria, which are represented by a point of the concen- 
tration-diagram, occupy all spaces in the /?,7-diagram and they do 
not coincide completely, nor partly. 
We take from the invariant equilibrium 
(Pa PI ee ee He 
a complex X of the composition 
X =a, PF, Ha, F, +. + ante Fats. 
Now we shall answer tbe question: if we bring this complex 
under such a P and at such a 7’, that it becomes metastable, into 
which other equilibrium will it then convert itself, when (while Pand 
T remain constant) the metastable condition passes into a stable one ? 
In order to answer this question, we consider in a P, 7-diagram 
the curve (/’,) which represents the equilibrium (/’,); when we 
bring the complex X under such a P and at such a 7’ that it is 
metastable, then it is represented by a point Q on the metastable 
part of curve (F,). This point Q is situated in the bivariant fields 
which are extended over the metastable part of curve (/’,). When 
the metastable condition passes into a stable one, then consequently 
one of the equilibria must be formed which are represented by 
those fields. When only one single field extends itself over the meta- 
