602 



According- to the rule, deduced in communication VI Faa^ must 

 on increase of pressure turn in such a way that the line Fa goes 

 ahead. Tiiis is in accordance with fig. 4. 



In the same way it is deduced that triangle Faa^, when a and a^ 

 are situated in the vicinity of h and h^, must turn on increase of 

 pressure in such a way that the line Fa^ goes ahead. 



Also, howe^•er, cnrves of quite another form may occur, viz. closed 

 curves; these are. therefore, situated completely within the triangle 

 and they are exphased. We imagine e.g. in fig. 12(1) the component 

 triangle to be drawn in such a way that the point F is situated 

 on the side BC and that the two curves fall within the triangle. 

 Both the curves then show a point of maximum- and a point of 

 minimumpressure. While a binary compound generally may be in 

 equilibrium, in addition to a series of ternary solutions, yet also with 

 two binary solutions, in the above mentioned case, therefore, it is 

 no more the case : now it may be only in equilibrium with ternary 

 solutions. 



Drawing the saturationcurves under their own vapourpressure and 

 their corresponding vapourcurves for ditferent temperatures, we may 

 distinguish two principal types; these are represented in fig. 5 and 

 6. In both the figures, however, the vapourcurves are omitted. At 

 temperatures below the minimum meltingpoint Tp the saturation- 

 curves under their own vapour pressure are circumphased ; at Tf 

 the curve goes through F and above Tf they are exphased. In 

 fig. 5 they disappear in a point H on the side, in fig. 6 in a point 

 H within the triangle. 



Fig. 5. 



Fig. 6. 



