J551 



tlie liquid phase leads to tlie knowledge wliioi) solid phase at a 

 definite temperature is the stable one, which the metastable, been 

 sufficiently carried out as yet. 



As we shall show presently, Dimroth has indeed, made very 

 important investigations in this directions, but an investigation carried 

 through systematically at different constant temperatures only can 

 bring us further here. 



To show this it is necessary' to subject Dimroth's important work, 

 which is of great interest for us here, to a closer examination. 



Dimroth') has made use liere of van 't Hoff's formula^) about 

 the ciiange of the ecjuilibrium through the solvent, but in a some- 

 wiiat modified convenient form. viz. in this shape: 



Cb L]i 

 in which C'.i and Cn indicate the concentrations of the substances 

 A and B in the stale oï (internal) equilibrium at a definite tempe- 

 rature. 



La t^nd Ln are the concentrations of saturation of A and B in 

 the pure solvent at the same temperature. G being a constant inde- 

 pendent of the solvent. 



Dimroth, now, points out thai inq)ortant conclusions ran be drawn 

 from this relation, which are of great importance for tiie preparation 

 of isomers transforming Ihcmsehes into each oilier. 



He says: sup|)Ose that for a certain temperature (t r= J, it follows 

 from this that when at this temperature we have .saturated an 

 arbitrary solvent with the two isomers .1 and B, and solid ^4 and 

 B lie on the bottom, the whole system remains unchanged in equi- 

 librium. It might iiave been stated here that the temperature at 

 which this takes place, would be the point of transition between 

 ^-1 and B, the temperature, therefore, at which the two solid phases 

 A and B are in etpiilii>rium. 



Ca Li 

 It G<^\. then ---<^— -. In this case the solution saturate with 

 Cb Lb 



respect to two solid isomers .1 and B will contain more A than 



corresponds to the state of eiiuilibrium. A consequence of this is 



that Ji is converted to B in the licjuid, B crystallizing out, and 



solid ^1 going into solution, till the solid .1 has entirely disappeared. 



The reverse will take place when (t^\. In connection with these 



considerations he says: "BringI man also zwei wech.selseitig mit 



1) Lieb. Ann. 377, 133 (1910). 



-) Vorlesungen iiber theor. u ptiys. Chemie, 219. 



