(15 
between the curves (Ll) and (2) the region (12) = 34; etc; then we 
find the regions indicated in fig. 2. Those regions are the same as 
in fig. 2 (I); only the region 23 from fig. 2 (I) is missing in fig. 2; 
it is replaced by the singular eurve (M) = F, + FP. 
In fig. 2 the region 14 extends itself over the metastable parts 
of the singular curves (M), (L) and (4); indeed this region contains 
the two indifferent phases /’, and /’,. 
Now we have let the phases #, and #, coincide and also /’, and 
F, in the concentration-diagram of fig. 2 (1), we might as well have 
made /’, and /’, coincide. Then we obtain however a same type of 
P,T-diagram as in fig. 1. Consequently only two different types of 
P,T-diagram may occur; they are represented in figs. 1 and 2. 
We are able to deduce the types of P,7-diagram also in the 
following way. In communication X we have viz. seen that we 
may distinguish three main types, viz. I, ILA and IIA. 
In main type L curve (J/) is monodirectionable; the ?, 7-diagram 
of a binary system has then the same appearance as that of a 
unary system. Therefore, it consists, as in fig. 2, of three one- 
curvical bundles; one of these curves represents then the three 
singular curves. [In fig. 2 they are the curves (M), (1) and (4).| 
In main type IJA curve (M) is bidirectionable and a middle curve 
of the (M)-bundle [fig. 3 (X)], we obtain then for a ternary system 
a type of P,7-diagram as in fig. 1. 
In main type IIB curve (J/) is bidirectionable and a side-curve 
of the (M)-bundle [fig. 4(X)]. As in this type, besides the (M/)-curve, 
still five curves at least have to occur, in binary systems a P,7- 
diagram of this type cannot exist. 
We can also find the types of P,7-diagram with the aid of the 
reactions, which may occur between the phases of the invariant 
point. 
In order to find the type of P,7-diagram, which belongs to the 
concentration-diagram of fig. 1, we consider the reactions, which 
may occur between the phases and the partition of the curves, resulting 
from those. 
bek, 
B) | (My | (FY) 
Hod ed E42, 
GELEEN EEN | CP) (FA | Ge): 
We see that this partition of the curves is in accordance with 
