$56 
(we — a)r + (y —B)s) dz + [(a@--—a)s + (y—B)t]dy=0. (10) 
(a, —«) r + (y,—y) 8] de + [(#,—2)s + (y,—y)t]dy=0. (11) 
This means that in this point the saturation line under its own 
vapour pressure comes into contact with the isothermic-isobarie satu- 
ration line of / (10) and with the liquidum line of the heterogeneous 
region LG (11). 
We can satisfy (10) and (11) by: 
y—B a 
= En . . . . . . . . t2 
dt av, S45 ( ) 
This means that the three points representing the solid substance 
F’, the liquid and the vapour are situated on a straight line. Hence, 
we find that on a saturation line of a solid substance / under its 
own vapour pressure, the pressure is maximum or minimum when 
the three phases (/’, 1, and G) are represented by points of a straight 
line, or in other words, when between the three phases a phase 
reaction is possible. | 
If we imagine before us the equation of the correlating vapour 
line we notice that when the pressure in a point of the saturation 
line under its own vapour pressure is at its maximum or minimum, 
this must also be the case in the corresponding point of the correlated 
vapour line. It then also follows that the correlated vapour line, the 
vapour saturation line of / and the vapour line of the heterogeneous 
region LG meet in this point. 
The previous remarks apply, of course, also to the boiling point 
line of the solutions saturated with #: in (6) and (7) dP must then 
be supposed = 0. 
Hence we conclude: 
When solid matter, liquid and gas have such a composition that 
between them a phase reaction is possible (the three figurating points 
then lie on a straight line) then, on the saturation line of the satu- 
rated solutions under its own pressure, the pressure is at its maximum 
or minimum; on the boiling point line this will be the case with 
the temperature. The same applies to the vapour lines appertaining 
to these curves. In each of these maximum or minimum points the 
three curves come into contact with each other. 
The properties found above have been already deduced by another 
way in the first communication. 
We will now investigate the saturation line of / under its own 
vapour pressure in the vicinity of point £. First of all, it is evident 
that one line may pass through point #. - 
For if in (8) we call c—a and y= @ it follows that dP = 0; 
(9) is En into : 
