769 



qiieiitly fii'st C//i fVom C towards //^ and afterwards again this 

 same line, but in opposite direction, eonsequcntly from ^^ towards 6^. 



Each vapour of' this straight vapour line Q/i can, therefore, be in 

 equilibrium with two diiFerent liquids, the one of branch A(/ and the 

 other of branch gn. 



We may express this also in the following way : when we have 

 an equilibrium F -\- L -{- (,r, tlien tliere exists under another pressure, 

 also an equilibrium F -\- L^ -\- G■^, in which L and L^ have a 

 different composition; (t and (r,, however, have the same coinposition.^ 



It is apparent from the deduction of fig. 2 that in curve Ay^ also a 

 point of maximumpressure can occur. This case is drawn in fig. 3; 

 Itn represents again the saturationcurve under its own vapourpressure 

 and 6^1 represents the corresponding straight vapourline ; M is the 

 point of maximumpressure, i)/j the corresponding vapour. The points 

 J/j, M, and F must of course ha situated on a straight line. 



While under the pressure Fm there occurs only one equilibrium, 

 viz. F -j- Lm -f- (TM■^ , under eacii })i'essure, somewhat lower than 

 J\\i there exist two equilibria, for instance F -\- La -\- (ra^ and 

 JT J^ r^^. J^ (J^.^ ; we can imagine these to be represented by the 

 threephasetriangles Fan^ and Fcc^ , when we imagine both triangles 

 in the vicinity of the line FMM\. It follows from the deduction 

 of the diagram that both these triangles turn their sides solid-gas 

 towards one another, consequently also towards the Hue FMM^ . 



Suppose, we want the curves ed and pt/ to move in fig. jI with 

 respect to one another in such a way that a point of minimum- 

 pressure occurs on the saturationcurve under its own vapourpressure, 



51* 



