1506 
Fig. 3 
From ‘the situation of the points J/ and m it is now evident that 
the arrows do not, as in the previous figures, indicate here the 
direction of the increasing pressure, but that of the decreasinx one. 
Let us now imagine in fig. 3 to be drawn the distillation curve 
of a liquid and its conjugated vapour curve. It is now evident that 
if the first does not intersect the saturation line under its own 
vapour pressure, the second will also not intersect the vapour 
saturation line and reversedly. We further perceive at once that in 
this ease the distillation curve will suffer no change owing to the 
appearance of the solid substance. 
When, however, the distillation curve, such as the curve rstuv 
in fig. 3, intersects the saturation line under its own vapour pres- 
sure, matters are different; the arrows on this curve rstuv indicate 
the direction of decreasing pressure, hence also the direction in which 
the liquid moves during the distillation. It is now evident that with 
a point of intersection s of the distillation curve of the liquid and 
the saturation line of # under its own vapour pressure must correspond 
a point of intersection s, of the distillation curve of the vapour and 
the vapour saturation curve of /’ under its own vapour pressure. As s, 
represents the vapour which can be in equilibrium with the liquid 
s, the distillation curve of the liquid must meet the line ss, in s. 
If no solid F occurred, the liquid 7 would, on distillation, proceed 
along the curve rstuv; now however, when it has arrived in s 
something else takes place. For if we withdraw from the liqnid s 
a small quantity of vapour s, the new liquid will be represented by 
a point of the line af’; we must then suppose the point a to be 
situated adjacent to s. The new liquid will now resolve into solid 
F and the solution « of the saturation line under its own vapour 
pressure. The liquid, therefore, does not proceed along the distillation 
curve stu, but moves, with separation of /’, along the saturation 
