1168 



start from the a and the i?-side, and in general possess a different 

 crystalline form. 



As Herbette ^) has demonstrated by an experimental way that 

 such a continuous transition between mixed crystals of different 

 crystalline forms occurs for potassium and tkalUuin tartrate even in 

 the stable region, it must be admitted that the contiiuiit}' in the 

 unstable region given in fig, 1, is a possibility, especially for mixed 

 crystals whose systems of crystallisation are closely allied to each other. 



On the other hand it should be pointed out, that it is very probable, 

 that iu many cases the continuity assumed here, does 7iot exist, and 

 the two halves of the ?-.i'-line, which refer to mixed crystals of 

 ditfeient forms, are not related. We might imagine that in this case 

 two S-.i'-lines occur, which proceed continuously from one axis to 

 another, as fig. 2 shows. The C-,i'-line cd would then relate to mixed 

 crystals of one kind, and ah to those 'of the second kind. The ^-.c- 

 line cd then indicates the ^-values of different mixed crystals, in 

 which the pseudo-comi)ünenl a is compelled by ,i to crystallize in 



1) Compt. rend. 140, 1649 (1905). 



