5J4 



of (he ? smftice. As well a satiii-alion- as a vapoiirsatiirationciu-ve of 

 the compound F exists therefore. Wiien we contemplate the two 

 curves with respect to each otiier. tlien either one complete!}' or a 

 part of both is metastable. 



When the point {F) is situated below the liquid- but above the 

 vapourleaf of the ? surface, the compound F only exists in vapour- 

 form. Then not a vapoursaturationcurve exists, but a metastable 

 saturationcurve of F, therefore a series of metastable solutions, 

 saturated with F. 



When the point [F) is situated below the vapour-, but above the 

 liquidleaf of the ? surface, the compoiind i^ exists only in liquid state. 

 Then not a saturation-, but a metastable vapoursaturation curve of 

 F exists, therefore a series of metastable vapours in equilibrium with F. 



When the point {F) is situated above both the leaves of the ? surface, 

 then the compound F occurs in liquid or in vapour-state, according 

 as below the point (7^") the liquid- or the vapourleaf is situated 

 the lowest. Then neither a saturation- nor a vapoursaturationcurve of 

 F exists. 



The four above mentioned cases appl}' of course also to the com- 

 pound F' . 



We now take a pressure and a temperature at which F and F^' 

 are both solid. The points [F) and {F') are then situated below 

 both the leaves of the C ^^urface and each of the compounds has 

 then a saturation- and a vapoursaturationcurve. 



We distinguish now four cases : 



1. the line {F){F') intersects both the leaves of the ? surface. 

 We cannot construct through the line [F] {F') a plane of contact 



on one of the leaves of the S surface; the two saturationcurves, there- 

 fore, do not intersect each other, nor the two vapoursaturationcurves. 

 The two saturationcurves niciv now be situated completely outside 

 each other, or the one may surround the other ; the same applies 

 to both the vapoursaturationcurves. Therefore neither a liquid nor a 

 vapour exists in equilibrium with F -\- F" . 



2. The line (F) {F') intersects the liquidsurface, but is situated 

 below the vapourleaf of the ^ surface. 



Because we cannot construct through the line {F^) {F') a plane of 

 contact on the liquidleaf, the two saturationcurves do noi intersect 

 each other, so that the one is situated outside the other, or the one 

 surrounds the other. 



We can (however) quite well construct two planes of contact on 

 the vapourleaf through the line (7^') (7^'). The two vapoursaturation- 

 curves, iherefoie, intersect each other in two points. 



