1218 
now in fig. 1 (II) we also imagine to be drawn the saturation line 
under its own vapour pressure of this temperature 7”, we notice 
that this intersects the line X/Y in two points. In fig. 1, therefore, 
a vertical line corresponding with the temperature 7” must intersect 
the curve X/Y in two points. 
If we take a temperature 7’” somewhat higher than 7'y we find 
that the vertical line corresponding with this temperature does not 
intersect the curve X/’Y in fig. 1. 
We now take the boiling point line of the compound # of the 
pressure Py, that of a somewhat lower pressure P’ and that of a 
somewhat higher pressure ?". As Q—wS< 0 it follows that that 
of the pressure Py has a form like curve a/°b of fig. 1 (II) in which, 
however, we must imagine the arrows to point in the opposite 
direction. From a consideration of these boiling point lines it follows 
that in fig. 1 curve Y/’)Y is intersected by a horizontal line corre- 
sponding with the pressure Pp in /’ only, and in two points by a 
horizontal line corresponding with the somewhat lower pressure P’. 
V > v therefore A >0 and 2>0; Q—aS< 0; Q—wS > 0. 
dP 
From (8) it follows that == is negative, from (9) and also from 
; 
(18) and (19) that d7’ is negative and dP positive. In fig. 2 d,Fd 
again represents the tangent at the point /’ of the not drawn melting 
point line; the dotted line passing through the point Fis the tangent 
in the cusp / of curve XFY. 
The fact that the curve X/Y proceeds from # towards lower 
temperatures and higher pressures may be deduced also in the following 
manner. From a consideration of the saturation lines under their own 
vapour pressure of the temperature 
Tr, the somewhat lower tempe- 
d rature 7”,and the somewhat higher 
temperature 7"", it follows that curve 
XI'Y in fig. 2 is intersected by the 
vertical line corresponding with the 
temperature 7’, in /’ only and in 
two points by the vertical line 
corresponding with the somewhat 
Fig. 2. lower temperature 7’. 
As Q—wS>0, the boiling point line of the solutions saturated 
with /” has, at the pressure Pp a form like curve afb of fig. 2 (II) 
in which, however, the arrows must be imagined to point in the 
opposite direction. If we imagine in this figure the tangent ALY, 
~ 
