524 
When F, and F, are the indifferent phases, then in (2) is u, = 
=p, =u. It follows then from (2): 
ua, — ua, +p,a,+u,a,+...+enpoeare=0. . (18) 
Now is: ud, tu, a, +: ..SeG, tat. 
in which: wp, >> a >> te, consequently also u >a. 
We may write, therefore, for (14): 
wa — 4d) Jela; Fars dn) =O sn 
or with the aid of (13). 
u(a, —4;) — efa,=-4)=0 202 ee (LG) 
As in accordance with (18) a,——a,, cannot be zero, it follows, 
therefore, from (16): u — a —= 0, which is not possible. The phases 
F, and F, cannot be, therefore, in (12) the indifferent phases; the 
curves (/’,) and (/’,) cannot coincide, therefore, in opposite direction. 
We shall call two curves, the stable parts of which are bordering 
one another, a monodirectionable pair of curves. [In fig. 2 g. (V) 
e.g. (A) and (B) or (B) and (C) or (G) and (F) ete.| Two curves, 
of which the stable part of the one curve borders the metastable 
part of the other curve, we call a bidirectionable pair of curves. 
[In fig. 2 g (V) e.g. (A) and (D) or (G) and (D) ete.] 
We may summarise the previous results in the following way: 
In each P,7-diagramtype the curves of each monodirectionable 
pair of curves may coincide in the same direction and the curves 
of a bidirectionable pair of curves may coincide in opposite direc- 
tion. In a P,7-diagram with the two curves (X) and (Y) and a 
bundle (Z), (X) and (J) however, cannot coincide. 
Now it follows from our considerations that we may distinguish 
three main types of P,7-diagrams. 
I. Curve (M) is monodirectionable | fig. 1]. 
The P,7-diagram has the same appearance as an ordinary LP, 7: 
diagram; as one of the curves represents however the three singular 
equilibria (J/), (#5) and (/7,41) consequently only n + 1 curves occur. 
Therefore the P,7-diagram has the same appearance as a P,7-dig- 
gram of a system with m—1 components. 
When eg. in the diagram of 4 components of fig. 2 (III) the 
curves A’ and F” coincide, then this diagram gets the same appear- 
ance as the diagram of 3 components of fig. 4 (II). [We have to 
bear in mind that the figs. 4 (11) and 6 (II) have to be changed 
inter se]. Curve (4), however, represents then the three singular 
equilibria. 
When in the diagram of 4 components of fig. 4 (IH) the curves 
