( 704 ) 
point in Q, and Q,, denotes the concentrations of the coexisting liquid 
phases at every 7, and the curve Q',, Q', indicates the concentra- 
tion of the third coexisting phase (vapour phase). The curve 7), = /(z) 
has been drawn higher in the figure. 
It follows, however, from the remark, Contribution XI, p. 440, 
Vol. XI, that the point P? need not even be present, and that yet 
the remaining part of the figure, but then between narrower tem- 
perature limits, may continue to exist. We might even imagine the 
circumstances to be such that the points P,, and P.q coincide, but 
then .Q, and Q, and Q’, and Q’, would have coincided already before. 
The second case is represented in fig. 40. Again Pis the projection 
d 2 
on the 7‚v-plane of the point of contact of the two surfaces ou ==) 
‘ip : 
and ils a The: fill ‘curve AQ: Pea Pan Q, Bete, ae: that of 
dv? 
G 
X=0 Nat 
Fig. 40. 
plaitpoints. The points P,, and P.¢ are the double plaitpoints. So 
4 a; 
