361 

 From equation (12) (13) now follows the relation 



VL i-L 



a,, X, 



(14) 



from which it appears that in the ideal case (he factors /\ and /, 

 of equations (6) and (7) become equal, so that the relative distance 

 in concentration, as far as A and B are concerned, has the same 

 value for the coexisting' liquid and vapour -phase L and G in the 

 four phase equilibrium oj the pseudo ternary system as the relative 

 distance betiveen the internal equilibria Lo and Go in the binary system. 

 Equatioi\ (14), therefore, says with reference to fig. 2 that: 



Be Bd 



Ae Ad 



'^~w 



Ag Af 

 If we now write equation (14) in the form : 



*Zi Xl Xg X,/ 



yL~ Yl ' y/ Y^ 

 we may remark that according to Dimroth's terminology : 



— • — = G 



y? ' Y,j 



If we introduce also this substitution, we get: 



^ = ^.G (17) 



yL Yl 



whereas Dimroth wrote: 



Ca Li 



— = —.(? (18) 



Cb Lb 



Now Xi and Yl indicate the concentrations of A and B in the 

 solution L (see fig. 2), which is saturate with respect to A and B, 

 Lj, and Lb representing the saturation concentrations of A resp. B 

 in the pure solvent. 



As a rule these are of course not the same quantities, but when, 

 as in the ideal case, the substances A and B do not influence each 

 other's solubility, this is the case, as also appears from fig. 2, for 

 from this follows immediately : 



Ca Bd Xl 



'■' = Ai=Ai=rl <'»' 



SO that Dimroth's formula is perfectly correct for the ideal case. 



