359 



In tliis inetliod it is quite immaterial whether .1 and B are 

 isomers or polymers. Whatever molecular weights we may assume 

 for the oalculatiou of the concentration ratios between .4 and B, 

 whether these are correct or wrong, all this is of no importance 

 wiiatever, because the factor f\ is not atfected at all by this. 



3. Dimroth's rc/at/on for isomers. 

 The relation of Dimroth. 



^=|^'.« (1) 



is not universally valid, and this is already seen l)y this that here 



— is written instead of --, in which La indicates the solubility of 

 Lb A/. 



La 

 A in the pure solvent. is therefore oof the ratio ot concentration 



Lii 



of A and B in the liquid L saturated with respect to .1 and B in 



Fig 1, but: 



Ca a 



La = -r- and Lb — -— . 

 Aa Bb 



This circumstance is to be explained by this that Dimroth's 

 formula only holds for the ideal case that even to the licpiid and 

 the vapour phases saturated with respect to the solid phases the laws 

 for the ideal solutions and gases may be api)lied, so that also a 

 mutual influencing between A and B is excluded. 



Accordingly it need not astonish us that this relation of Dimroth 

 has a very limited validity, but on the other hand it can also give 

 us further information about these ideal cases. 



I shall demonstrate this by the aid of fig. 2, which likewise holds 

 for an ideal ternary system. We see that this fig. differs from fig. 1 ; 

 first in this that the solubility isotherms, at least for so far as they 

 represent stable states, are straight lines, which join the points a 

 resp. «1 with the angular point B, and the points h resp. h^ with 

 the angular point A, which expresses that the substances A and B 

 do not influence each other's solubility. Secondly it is noteworthy 

 that the isotherms for the internal liquid resp. vapour equilibrium 

 are also straight lines, because it is supposed here that A and B 

 are isomers. And in the third place it is assumed that A and B 

 do not form mixed crystals. 



For the internal e(|uililtriuiu in o\o\\ li([iiiil phase, hence also in 

 L„, liolds : 



24* 



