m 



pressiive. For onl}' in this case e.g. tlie situation of the line for the 

 internal eqnilibriiini in the li(|ui(l with respect to the j)scudo s^yslem 

 will shift with the pi'essine, and if tiiis displacenient is snch tiiat 

 the point ^ moves downward with respect to the pseiido binary 

 TjA^-figure, /.^ will coincide with c, ^S'^ with d and >S'2 with e at a 

 given pressure, or in other woids under this pressure two solid 

 moditications of the unary system will be in ecpiilibrium with each 

 other and with their melt at a definite temperature (triple point 

 temperature). 



At this temperature the two modifications have therefore the same 

 melting-point pi'essure, so that this temperature can also be called 

 a transition temperature under the melting-point pressure. 



If we raise the pressure still more, we get a 7',,i'-figure as given 

 in Fig. 5, from which it appears that whereas the direction of the 

 lines for the intei'ual equilibrium in the solid phase excluded the 

 appearance of a stable point of transition at lower pressure, it must 



now at higher pressure neces- 

 -/ .sarili/ lead to a transition point. 

 We see further that the solid 

 phase which appears at the 

 stable point of solidification now 

 lies on that mixed crystal line 

 on which the solid phase of the 

 metastable melting equilibrium 

 lay before, and vice versa, so 

 that the form of crystallisation 

 of the solid phase at the stable 

 point of solidification will now 

 be equal to that in which the 

 metastable phase showed itself 

 at a pressure belotu the transi- 

 tion pressure. 



On further increase of pressure 

 the points I^ and s^ move still 

 more to the left, and the transi- 

 tion equilibrium gels deeper and deeper below the equilibrium of 

 melting. 



The P, T-projections of the points s^ and I^, at different pressures 

 will form the stable melting-point line, that of the point s^ and /j 

 the metastable one,'-- whereas those of the points .s''.^, s\ form the 

 transition line as indicated in fig. 3. 



It therefore appears from the foregoing that the transition from 



