This equation is again tiie same as eqiiatiuii (20) in llie first 

 communication. 



2. Appinu'iit co/ilfi((IirtioH hctwi'cn theoi'ij and practice. 

 DiMROTH '), who wrote equation (18) as follows : 



C'aj C 



r, =7^(^ (20) 



has pointed out that, the direction of the isomeration l»eing exclusively 

 dependent on tlie factor G, this must lie independent of the nature 

 of tiie solvent. 



Experience, says Djmkoth, is in contradiction with tiiis, for it is 

 known that isomers can be transformed into each other by treat- 

 ment with different solvents. 



In this connection I must point out in the first place that there 

 can be question of a test of formula (20) only when we start from 

 a solulion saturate with respect to A and B in contact with the 

 two solid phases. Only in one case tiiere will then come no change 

 in this state, viz. when the temperature of the system is exactly 

 the transition temperature of the two solid phases. In all other cases 

 a transformation will take place independent of the solvent, in which 

 the metastable solid modification disappears, and the stable one 

 remains. For some systems this transformation will proceed slowly, 

 but then we must try to accelerate the i»rocess catalylically. 



When, working in this n'liij, we find deviations, it will no doubt 

 have to be ascribed to this that equation (20) is applied to ?iy?z-/(:/fa/ 

 cases, or to liie case of pohpnei-». That practice is really in agreement 

 with theory, can be demonstrated in such a case in a simple way 

 by application of the luiiversitUij liKldimj e(|uation (6) of the preceding 

 communication : 



A'/, . ^ 



.'1 V 



in the way indicated there. 



That isomers can be converted into each other by treatment with 

 different solvents is an entirely different phenomenon. By this we 

 undei'stand namely that when e.g. the <t-form is dissolved in a certain 

 solvent, and we then bring the solution to crystallisation in some 

 way or other, the /?-form appears. 



ij Lieb. Ann. 877, 1^7 (TJIO). 



