1348 
The temperature t,, which lies slightly above this temperature, 
therefore, yields the P,X-section Fig. 3, in which we see that the 
lines for the internal equilibrium in the stable solid modification 
S,, and in the metastable modification 5,,, meet the mixed crystal 
lines Se, S’ay and So, S'z,, of the pseudo system at S',, and S',, 
which means that in case of unary behaviour, a transition of the 
solid phase Sy, into S',, will take place there at constant pressure, 
provided no retardations oceur, so that the modification S,,, which 
was metastable at lower pressures, now for the first time appears 
stable. If the phase Sy, has been entirely converted, then on further 
compression the pressure will again rise, and now the internal equi- 
librium of the stable phase will move along the line Sn se 
Accordingly at this temperature enantiotropy is found with variation 
of the pressure. 
Fie. 4 has reference to the tem- 
perature of the metastable melting- 
point D of the unary system. The 
only peculiarity presented by this 
P,X-section compared with the 
preceding one is this that the meta- 
stable prolongation of the line for 
the internal equilibrium in the 
vapour exactly meets the point 
where the metastable prolongation 
of the vapour branch aG in the 
pseudo binary system intersects 
the vapour branch of the meta- 
stable liquid-vapour equilibrium. 
This means, therefore, that in meta- 
stable state in the unary system 
coexistence of solid, liquid and 
vapour, viz. Su, Go, + La ap- 
pears, or in other words that in 
this section the metastable melting 
equilibrium under the vapour pres- 
SUPE OCEUTS. 
Fig. 5 corresponds with t,, a 
a x p 
3 the eutectic temperature of the 
Fig. 4. pseudo binary system. In connec- 
temperature lying a little below 
“tion with what precedes this figure 
is clear without further explanation. 
