674 



mediate portion, and here a line pq can be given for the Uinit of 

 coexistence of Sa + Sb , because either Sa or Sb has reached its 

 limit of coexistence there, wiiich makes it impossible for the said 

 coexistence to occur an}^ longer. 



It follows therefore from this that the lines /; and }n extend 

 metastable to a definite temperature above the eiitectic one. 



Transition from monotropi/ to enantiotropy. 



As is known it often happens that a substance under the va|)Our 

 pressure presents the phenomenon of monotropj. whereas nnder 

 higher pressure enantiotropy takes place, as has e.g. been indicated 

 in the PT-figure 3. 



The theorj of allotropy again enables us to get a clear insight 

 into the signification of this phenomenon. 



Suppose the 2',.Y-figure 4 lo hold for a pressure above the triple 



a 



A 



Fis. 3. 



Fig. 4. 



/ 



point 0^ and below the triple point 0^, then according to the said 

 theory the conclusion may be drawn from the fact that at higher 

 temperature enantiotropy occurs, that the situation of the internal 

 eqiiilibrium ivith respect to the pseudo system, is dependent on the 



