corresponding sublimation-pressures, we obtain the sublimationcurve 
of the substance F. [Confer for instance curve aX in fig. 3 (LID). 
Previously we saw that this curve ends in the uppermost sublima- 
tionpoint A; at higher temperatures viz. is formed solid #” + liquid 
+ vapour. When the formation of liquid fails to make its appear- 
ance, this curve may be extended of course. 
Ul. The equilibrium #4 G; F is a binary compound, G is a 
ternary vapour. 
With the aid of the vapourleaf of the ¢-surface we find that the 
vapours, which can be in equilibrium with solid #, form again a 
curve. When # is a binary compound of B and C, this vapour- 
saturationcurve has two terminatingpoints on side BC; the point / 
is always situated between these two terminatingpoints. Therefore 
we call this curve circumphased again. Consequently the binary 
compound can be in equilibrium with a series of ternary vapours and 
with two binary vapours, consisting of B and C. The equilibrium 
is determined by (1) when we put herein a=0O. We find from 
this for the vapoursaturationcurve : 
Le, 7, + (y,—8) sl dz, + [7, 5, + (y,—A) 4) dy, =O . - (6) 
(We find this also from (4) by putting herein a = Oand dP = 0}. 
For a terminatingpoint of this curve on the side BC is #,=0 and 
Lim «,7,= RT; the tangent in this terminatingpoint is conse- 
quently fixed by : 
(2) Ct BT + GSB og aad) + gif E 
kn ae ne a 
The first expression is generally applicable ; the second only when 
the gas-laws hold good. 
The rules mentioned sub I apply to the movement of this curve 
on change of P or of 7’. 
In a similar way as we have acted in I, we find also here, that at 
each temperature a definite pressure exists, under which the vapour- 
saturationcurve reduces itself to the point /’; this pressure is the 
sublimation-pressure of the binary compound /”. Therefore we may 
draw in a P,7-diagram a sublimationcurve of #. 
IU. The equilibrium “+ G; F is one of the components, G is 
a ternary vapour, 
We find that the vapours, being in equilibrium with solid #, form 
again a curve. When F is the component B, this vapoursaturation- 
curve has two terminatingpoints, the one on side BA, the other on 
side BC, The component B can, therefore, be in equilibrium with 
du, 
