REPRESENTATION BY ZETA FUNCTION 309 



conceivable systems (12), only L(g) + solid W and L(h) + 

 solid X are stable. 



Liquid g is saturated with respect to solid W, and liquid h 

 with respect to solid X. All liquids between W and g are 

 supersaturated with respect to solid W, all liquids between h 

 and X with respect to solid X. All liquids between g and h 

 are unsaturated. In Fig. 10 the liquids g and h are repre- 

 sented by the points g and h of the line 3.3'. 



(iv) T{X) > T{W) > T = T{e) (case of Fig. 8). When 

 the points of contact g' and h' of Fig. 7 coincide we obtain Fig. 

 8, in which the f-curve and the straight line (W)(X) touch 

 one another in the point e'. In this case we see that of all 

 conceivable ^-points of Fig. 8 only those of the line (W)e'{X) 

 represent stable states. Since the point e' lies not only on this 

 straight line but also on the f-curve, the point e' may now 

 represent not only solid W + solid X but also the liquid of 

 composition e. We now have a f-line of which not only the 

 two end points but also a third point e' represent stable phases. 

 Every point of the hne {W)(X) can represent therefore a system 

 soHd W + solid X, whilst each point of the part (W)e' can 

 represent also a system L{e) + solid W, and each point of the 

 part e'(X) also a system L(e) + soUd X. From this it follows 

 that of all liquids only the liquid e is now stable, whilst of all 

 conceivable systems (12) only the systems : 



L(e) + solid W, L{e) + solid X, 

 solid W + solid X, 



(13) 



are stable. Since L(e) is saturated with respect both to W and 

 X, therefore also the three-phase system 



L(e) + solid W + solid X (14) 



can exist, in which the reaction 



solid W + solid X ^ L(e) (15) 



can occur. For we have already seen that the liquid e has the 

 same f as a system, solid W -f- soHd X, with the composition e 



