74 



In (ig. 2 some sattiratioiicurves under their own Viipourpressure 

 of A [ak,b l,c iii,on) and of B {li i, <j L f m, pn) are completely or 

 partly drawn. When iji one of the hinarv systems, e.g. in CB, there 

 exists a point of maximumtemperatnre H' , then also there occur 

 saturationcurves as the dotted curve qr. As long as we consider 

 solutions, not situated in the vicinity of A B, the vapour region is 

 represented by point C. When we consider, however, also solutions 

 in the vicinity of A B, the vapour region expands over the triangle. 



• Consequently, when we de- 

 duce the saturationcurves 

 under their own vapour-pres- 

 sure, assuming that the 

 vapour is represented by C, 

 we may do this only for 

 solutions, not situated in the 

 vicinity of AB. For points 

 of the curves in the vicinity 

 of AB we take the case, 

 treated already in communi- 

 cation XIII that the vapour 

 pjo. 2 is ternary. The same applies, 



as H' is situated in the vicinity of B, also to the curves in the 

 vicinity of H' . 



If follows from the deduction of the saturationcurves that the 

 pressure, e.g. along a k, continues to decrease from a; only in the 

 vicinity of ,(:, a point of minimumpressure may perhaps be situated. 

 As the pressure in b and consequently also in the minimum possibly 

 occurring is exceedingly small and practically zero, we can say : 

 along the saturationcurve of a component the pressure increases 

 from the solution free from water (k) towards the pure solution {(i). 

 The pressure of the solution free from water is practicalh zero. 



Let us now take a binary compound of A and B (for instance 

 an anhydric double-salt); it may be imagined in fig. 2 to be repre- 

 sented by a point F on AB. When we leave out of account satura- 

 tioncurves in the vicinity of F, we may say that the saturation- 

 curves under their own vapourpressure have two terminatingpoints, 

 both situated on AB. As the pressure is again very small in both 

 the terminatingpoints, it follows: alojig the saturationcurve of an 

 anhydric double-salt, the pressure increases from each of the solutions 

 free from water towards the pure solution. 



c) The solid substance contains the volatile component C only^ 

 This is for Distance the case when an aqueous solution of two 



