716 
tig. 1. It is evident that we can also find easily the type of P,7- 
diagram with the aid of this partition of the curves. 
We find from the concentration-diagram of fig. 2 
is 
(H,) | (M) | (Fs) 
Fp Re. de 
AH) |H) | As) A) EN) | A) | 7). 
Hence we find a type of P,7-diagram as in fig. 2. 
We are also able to deduce the types of P?,7-diagram with the 
aid of the series of signs. In order to find the series of signs, we 
have to know two reactions, each between the four phases of the 
invariant point. We can easily deduce those reactions from the 
concentration-diagrams of figs. 1 and 2; for the concentration-diagram 
of fig. 1 we find then series of signs 1; for that of fig. 2 the series 
of signs 2. 
Series of signs 1 (fig. 1) Series of signs 2 (fig. 2) 
Pe en cl EER LD ieee 
a one me bee io 
OTE Ol + 
— 0.0 + = 0. | Or 
— + — 0 — + + 0 
In series of signs 1 F, and #,, in series of signs 2 F, and F, 
are the indifferent pbases; they have opposite signs in series of 
signs 1 and thev have the same sign in series of signs 2. The 
positions of the curves with respect to one another as in the 
figs. 1 and 2 follow immediately from those series of signs. 
It is apparent from the previous considerations that two types of 
P,T-diagram | figs. 1 and 2] may occur in binary systems with two 
indifferent phases. Those types are in accordance with the rules 
which we have deduced in the general. considerations |Communica- 
tion X|. We found amongst others: 
1. The two indifferent phases have the same sign or in other 
words: the singular equilibrium (J/) is transformable into the in- 
variant equilibrium (J/) and reversally. Curve (.J/) is monodirection- 
able; the three singular curves coincide in the same direction. 
| fig. 1 (X)]. Tine 
2. The two indifferent phases have opposite sign or in other 
words: the singular equilibrium (J/) is not transformable. Curve 
(M) is bidirectionable, the two other singular curves coincide in 
opposite direction ! fig. 2 (X)]. 
