312 SCHREINEMAKERS art. h 



it becomes. Hence the point (X) lies at first between X' and 

 s; then it coincides with s at a definite temperature, which we 

 shall call T{s), and afterwards it lies below s. If we leave out 

 of consideration the occurrence of solid W, we may now dis- 

 tinguish the following three cases. 



(i) T{X) > T > T(s). We imagine the point (X), which is 

 now situated between X' and s, represented by p' in Fig. 5. 

 If we now draw the tangent p'd', we see that of all conceivable 

 f-points of Fig. 5, only those of the parts TF'a' and h'd' of the 

 f-curve and those of the lines a'b' and d'p' represent stable 

 states. From this follows: all liquids of Wa and hd (Fig. 5) 

 are stable; all liquids between a and h separate into the system 

 L{a) + L{b); all liquids between d and X are supersaturated 

 and pass into the system L(d) + solid X. Consequently, of 

 all conceivable systems, only L(a) + L(b) and L(d) + solid X 

 can occur in a stable state. We imagine these liquids a, h, 

 and d represented by the points a, b and d of the line 1.1' in 

 Fig. 12. 



(ii) TiX) > T = T{s). Now we imagine the point (X) at 

 the point s of Fig. 11. We see that, of all conceivable f -points 

 of Fig. 11, only those of the part W'z' of the ^-curve and those of 

 the line z'u's represent stable states. This line z'u's, just like 

 the line {W)e'(X) of Fig. 8, has a special property, namely 

 that not two but three of its points represent stable phases, 

 i.e., z' and u' represent the liquids z and u, and s the solid sub- 

 stance X. From this follows: of all liquids, only those of Wz 

 and the liquid u are stable (Fig. 11). Of all conceivable systems, 

 only 



Liz) -f- solid X, L{u) + solid X, L(z) + L{u), (16) 

 and the three-phase system 



L{z) + L{u) + solid X (17) 



are stable. We see that two liquids now exist, namely z and u, 

 both of which are saturated with respect to solid X. 



In the same way that we deduced reaction (15) for the three- 



