3G8 



as in fig. J, lie pretty mucli on tlie 7J-side, it may occur tiiat in 

 consequence of the greater concentration of B than of ^, the number 

 of nuclei for the metastable modification -B,, reaches that value first, 

 at which spontaneous crystallisation sets in. In this case, therefore, 

 the metastable modification deposits from the supersaturate solution, 

 and if under the given circunislanccs the velocity of Conversion is 

 small, Ihe metastable modification that has crystallized oid, con- 

 tinues to exist. 



If, therefore, the situation is as Fig. 1 indicates, it is very well 

 possihli- tiiat when the stable modification A„ is dissolved in C' at 

 higher teuiperatiire, i.e. at such a temperature that the internal 

 equilibrium is entirely or almost entirely established, the metastable 

 form is deposited when the solution is cooled. 



For one solvent the situation will be as is indicated in Fig. 1, 

 whereas this situation will be less one-sided when another solvent 

 is used, and in this probably lies the explanation of the fact tliat 

 by means of one solvent from the stable form the metastable form can be 



Fis. 2. 



