54 r> 



There exists therefore no hciiiid saturated with F -\- F' . Two 

 vapours exist however, each of whicli may be in equilibrium, with 

 F+F'. 



3. The line (F) {F') intersects the vapourleaf, but is situated 

 below the liquidleaf of the ? surface. 



It is evident, that now the two saturationcurves intersect each 

 other in two points, while the tw^o ^'apoursaturationcurves are situated 

 outside each other or the one sui-rounds the other. Therefore two 

 solutions exist, saturated with F -\- F\ but not a vapour which can 

 be in equilibrium with F -\- F' . 



The equilibria existing in the tliree cases treated above may become 

 completely or partly metaslable, by the occurrence of the heterogeneous 

 region LG. Also it is evident, that in the previous cases not yet a 

 fourphaseequilibrium F -\- F' -\- L ^ (t can exist. 



4. the line {F){F') is situated below the two leaves of the ? surface. 

 We can now construct through the line [F) {F') two planes of 



contact on each of the two leaves of the S surface. The two saturation- 

 curves therefore, intersect each other in two points, situated on both 

 sides of the line FF' . The same applies to the two vapoursaturation- 

 curves. Therefore two solutions exist, saturated with F -\- F' and 

 two vapours, saturated with F -\- F' . 



In tig. 1, z and u are the points of intersection of the two satu- 

 rationcurves ; the points of intersection of (he two vapoursaturatiori- 

 curves ^^i Ij^ and .i\ ij^ have not been drawn ; w^e shall call these z^ and 

 u^ ; we imagine z^ on the same side of the line FF' as the point z, 

 and u^ on the same side as u. Under this pressure and at the tem- 

 perature to which tig. 1 applies, the systems F -\- F' -\- \k[mé z , 

 J.-^ j^ P' j^ liquid u, F + i^' -f vapoiu' c^, and F + F' -\- vapour u, 

 occur. Of these four threephaseequilibria of fig. 1, only the two 

 first however are stable. 



Now let us contemplate a point of intersection of two saturation- 

 curves and the i)oint of ijitersection of the two vapoursaturation- 

 curves situated on the same side of the line FF' (therefore in fig. 1 

 the points z and z^, or a and u^). If we imagine that through the line 

 [F){F') the two planes of contact on both the leaves of the C surface 

 are constructed, then the one point of contact is usually always 

 situated above the other surface. Because the projections of the two 

 points of contact of these surfaces represent the above mentioned points 

 of intersection, only one of both these points of intersection will 

 represent a stable phase. 



Therefore, if we have a stable solution saturated with F -\- F' , 

 then the vapour saturated with F -\- F' , being situated on the same 



