1020 
The regions are indicated in diagram (3) by placing between 
parentheses the two missing phases; the meaning of (AF) is e.g. 
the region with the phases B, C, D, and BE. 
Altogether we find 15 regions; some of these regions extend over 
one or more curves; this is indicated in the diagram by horizontal 
connecting lines. 
The same as in the P,7-diagram itself, we can easily deduce the 
position of the regions also in the symbolical representation. 
We have e.g. to find the region (A /') between /” and A’; between 
F’ and D’ the region (DF), which extends itself consequently over 
A’; between /” and B’ the region (BF) which extends itself, 
therefore, over the curves A’ and DY’. Between /” and C” we find 
the region (C/’); this region CF) does not extend itself over the 
curves A’, D’ and B’, for in that case it would extend itself also 
over the metastable part of curve F”, which is not allowed; con- 
sequently it goes starting from F” over curve £’ towards C’. 
Between /” and £”’ we find the region (ZF). When we act in the 
same way with each of the other curves, then we find a partition 
of the regions as in the symbolical representation (3). 
In this diagram (3) we see again the confirmation of the rule that 
each region, which extends itself over the stable or metastable part 
of a curve Fp, contains also the phase fp. We see e.g. that the 
regions BF), (DF) and (A/’) extend themselves over the metastable 
parts of the curves C’ and £”’; each of these regions contains the 
phases C and £. The regions (BF) and (DF) extend themselves 
over the stable part of curve A’; both the regions contain the phase 
A. The region (AL) extends itself over the stable parts of the curves 
D’, B’ and C” and over the metastable part of curve /”; it contains 
the phases B, C, D, and F; ete. 
8. Systems with an arbitrary number of components. 
Up to now we have applied the method for deducing the 
P, T-diagrams only on binary, ternary, and quaternary systems. We 
have acted in that case in the following way. 
We represented the compositions of the phases, occurring in the 
invariant equilibrium, by points in a concentration-diagram. This 
concentration-diagram was a straight line for binary systems, for 
ternary systems a plane, for quaternary systems the space. 
The points; which indicate the compositions of the phases, may 
be situated with respect to one another in these diagrams in different 
ways; we found for binary systems one position | fig. 2 (I)|, for 
ternary systems three different positions |fig. 1, 3 and 5 (II)], for 
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