540 

 Chemistry. — "Equilibria in ternary si/steiuö-." X. By Prof. B\ A. 



H. SCHREINEMAKERS. 



After having deduced in the previous cornmuniciition the diagrams 

 for a constant temperature (the saturation- and vapoursaturation- 

 curves under their own xapourpressure), and for a constant pressure 

 (the boilingpointcurves and their corresponding vapourcurves), we 

 will deduce now the diagrams for a constant temperature and 

 pressure. We may act for this in tiie same way as in communi- 

 cation I. For this we imagine for instance in figure i (I) besides 

 the saturationcurve of the compound F also one of the compound 

 F' . Both these saturationcurves may then be situated either outside 

 eacli other or they may intei'sect each other, or the one may 

 surround the other. We imagine both curves situated completely 

 in the lic{u id-region. 



Because the lieterogeneous region shifts on decrease of pressure in 

 such direction that the liquidregion becomes smaller and the vapour- 

 region becomes greater, under a certain piessure the liquid-curve 

 e (/ of the heterogeneous region will touch one of the saturationcurves. 

 When it touches that of F. we obtain figure 2 (I) wherein the 

 saturationcurve of F' is to be imagined. This is then still com- 

 pletely situated in the li((ui(lregion and may be situated with respect 

 to that of F in the abovementioned ways. Of all the solutions 

 saturated with F or with F' at this pressure, therefore, only one 

 exists, namely saturated with F, that can be in equilibrium with vapour. 



On further decrease of pi-essure figure 3 (I) now arises ; hereiji 

 we imagine the second saturationcurve, still completely in the liquid- 

 region, and whether or not intersecting that of F. Of all solutions 

 saturated with F or witii F' at this pressure now two liquids exist, 

 saturated with F {a and b) which may be in equilibrium with 

 vapour («1 and b^). On further decrease of pressure very many 

 cases may now occur. At first we assume that both the saturation- 

 curves are situated completely outside each other and rest also out- 

 side each other in the comtemplated pressure-interval. On decrease 

 of pressure the heterogeneous region shifts over the saturationcurve 

 of F, attains at a certain pressure the saturationcurve of F' , and 

 on further decrease of pressui-e shifts also over this. 



We may distinguish for this two principal cases: 



1. the saturationcurve of J^ is situated already completely outside 

 the liquidregion before the liquidcurve e d of the heterogeneous 

 region touches the saturationcurve of F' ; 



2, the saturationcurve of F is situated still partly in the liquid- 



