( 285 ) 



volume changes, as is the case with saturated vapour. From this 

 follows the well known property that at the critical point — ( — ) 



for saturated vapour is equal to — ( t;^; 1 • 



P \oTJr 



If with a binary mixture we pass from one homoj>eneous phase 



to another, at which v is increased by dv, T by clT and x by dx, 



then : 



If I — I =0, as is the case at the critical point of the compo- 

 nent, then : 



also for such variations in which the volume changes. 

 The differential equation of the surface of saturation : 



holds for the transition of an homogeneous liquid phase to a subse- 

 quent one and in the same way : 



-..dp = ^^ + ('^'^ - •^••^) (,dvJ> 



for the transition of an homogeneous vapour phase to a subsequent one. 



If the first liquid phase and the first vapour phase is the critical 



phase of the component, the three last equations must be identical, 



«'21 «'12 f^p\ ^ —^' f^p\ 

 and so — — = — — 1= — - , or — — — 1 ^ 1 



Tv^^ Ti\^ \dTj,.^j. Tu — Tit ydTj^.^i: ' 



In the same way ^— ] = — — , as has 



been proved above as holding for the critical point of the component. 

 From the general equation : 



(¥) 



follows, when i\ — v^ is infinitely small. 



'V, 



X^—X^ 7Jj Uj /d/> 



A-j MRT \hxJ„T 



and 



