866 
order to act in accordance with our determined assumption that C 
is the component with the highest vapour pressure the boiling point 
of C has been taken lower than that of A and 5. 
We now also take a polythermic-isobarie saturation surface of F. 
At the assumed pressure /P, there exists, for an entire series of 
temperatures, at each temperature a definite saturation line of F. 
If these are put on a temperature axis, the polythermic-isobaric 
saturation surface is formed which we can represent by fig. 7 in 
which however, we must imagine P to be replaced by 7’; we will 
call this figure fig. 7a. 
The figs. Ta and 8 apply only to one definite pressure; if this is 
altered they change their situation and form. On increase of pressure 
both surfaces of fig. 8 move upwards; the saturation surface of the 
figure Ta can move upwards as well as downwards. This depends on 
whetker on melting, there is an increase or decrease of volume. 
As however, a change in pressure causes, as a rule, a comparatively 
small ‘change in the melting point of a substance, the movement 
of the saturation surface of the substance /’ will be slower than that 
of the two surfaces in fig. 8. 
We now imagine the saturation surface of the fig. 7a to be intro- 
duced in fig. 8 and in such a manner that the point / lies above 
the liquidum side. The section is then the boiling point line of the 
solutions saturated with /’; the correlated vapour line has, as seen 
from the figure, shifted towards the vapour surface. A projection on the 
component triangle gives a circumphased boiling point line of the 
solutions saturated with fand a circumphased and an exphased vapour 
line. We thus again obtain the figures 7 (1) or 11 (1) in which 
however, the arrows, indicating the direction of increasing tempera- 
tures, must be supposed to point in the opposite direction. 
On further increase in pressure, the point F’ first arrives at the 
liquidum surface, then the liquidum surface comes into contact with 
the saturation surface of / from which follow the previously 
described boiling point lines of the saturated solutions and their 
correlated vapour lines. 
In place of the saturation surface of / we could also have consi- 
dered the vapour saturation surface of # and its movement in regard 
to the vapour surface of the system LG. We will refer later to the 
vapour saturation surfaces of a solid substance, in connection with 
another investigation. 
We have already stated above that the vapour surface, when the 
vapour contains two components only, reduces itself to a vapour 
curve, and to a point when the vapour contains only one component. 
