772 



The ratio a\:x has a defuiile value herein, as it follows from (5). 

 When we eliminate (/// from (10) and (11), dien we lind : 





RTdx =z ['3F 4- {y-[i} l\ - yv] dP . . (12) 



The quantities in die coefficient of dP relate all to the binary 



equilibrium F -\- L -{- G. When we call A F^i the change of volume, 



when between the three phases of this binary equilibrium a reaction 



takes place, at which the unity of quantity of vapour arises, dieii is : 



{y-^)Al\=^V+{y-i3)V,-yv .... (13) 



Consequently w^e may write for (12) : 



-=en-^)l.^-- (-) 



Now we introduce again, as in (XI) the perspective concentrations 

 of the substance .4 in liquid and gas; it is evideid that the per- 

 spective concentration S^ is equal to the real concentration .c, of .1 

 in the vapour; we tind for the perspective concentration of A in 

 the liquid : 



5:=-*— (15) 



so that w^e can write for (14) : 



When the vapour contains the three components, then, as we have 

 seen previously (14) (XI) is true; when we replace herein S^ by .I'j, 

 this passes into (16). 



It follows from (Kj) that the sign of the change of pressure in 

 the ends h and n of a saturationcurve under its own vapourpressure, 

 depends on the sign of AT,. Now LV, is almost always positive 

 for the binary equilibrium F^L-\-G and it is only negative between 

 the points i^'^and H [tig. 5 (XI) and fig. 6 (XI)]. Consequently A V, 

 is positive in the points h and n of figs. 2 and 3, also in the point 

 k of fig. 5 (XI) and 6 (XI) ; A F^ is negative in the point n of the 

 two last figures. Further it follows that the sign of the change of 

 pressure is not determined by the ratio .i\ : .;; (the partition of the 

 third substance between gas and liquid) but by the ratio S : x^ (the 

 perspective partition of the third substance between gas and liquid). 



Let us take now a liquid of the saturationcurve under its 

 own vapourpressure in the vicinity of the point /i of fig. 2, for this 

 we imagine triangle Faa^ in the vicinity of the side BC From the 

 position of Fa and Fa^ with respect to one another, foUowa 



