1215 
dP B Q-uS 
fe as oe ee 
in which gp and A have the same significance as in communication 
UI), namely 
C D 
A arid == ~ 
A B 
and further: 
Cari ste er AN 
26? BC-—-AD 20> BC—AD 
wherein, as in the previous occasion, we take BU — AD > 0. 
Let us first take a P, 7-diagram such as in fig. 2 (IV) and 3 (IV). 
As. B = H—-n is always positive, dP has the same sign as Q— ws. 
In communication (ID we have seen that Q—wS is negative when 
the boiling point line, of the solutions saturated with /” passing 
through /’ is curved in the point / towards O. The point O here 
represents the component occurring in the vapour. The boiling point 
line then has a form like the curve a/’é in fig. 1 (ID. dP now 
being negative, the P,x-curve must have a form like c/’d in 
fe, CRY). 
If the boiling point line of the solutions saturated with /’ is 
curved in the point /’ away from the point O so that it presents 
a form like curve al’) in fig. 2 (ID, Q—wsS will be positive. From 
the value of dP from (9) it now follows that the P, «-curve must 
have a form like curve cl’d of fig. 3 (IV). 
In order to tind the 7,z-curve in the vicinity of the point /’ we 
must distinguish two cases. 
V>v or A>0O. If Q—AS is negative, the saturation curve of / 
under its own vapour pressure is curved in the vicinity of towards 
Q and, therefore, has a form like curve a/b in fig. 1 (ID); dT’ is 
now negative and the .z-curve has a form like curve cl’d in 
fig. 2 (IV). If Q—AS is positive the saturation line of / under its 
own. vapour pressure will have a form like a/’) in fig. 2 (ID; d7’ 
from (9) is now positive and the 7z-curve has a form like c/’d in 
fig. 3 (IV). 
V-<v or A<O. If Q—AS is negative the saturation curve of 
J’ under its own vapour pressure will have a form like curve al’) 
in fig. 4 (11); @7Z’ from (9) is now positive and the 7z-curve, has 
consequently a form like curve c/"d in fig. 3(IV). If Q—‘S is 
positive the saturation curve of /” under its own vapour pressure 
will have a form like curve a/’/ in fig. 3 (11); d7’ from (9) is now 
negative so that the 7’,r-curve has a form like curve cf” of fig. 2 (LV). 
19 
dr UE Store KO) 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
