175 



6Vi, and consequently no Nupoiir exists of the composition F, the 

 curves ed and pq, therefore, cannot toucli one another. 



Let us now consider the tangents to the liquid-curve and to the 

 saturationcurve under a constant pressure in the point q (fig. 1); 

 as the vapour, belonging to this liquid, may be represented either 

 by a point q, situated between q and F or by a point q^ between 

 F and 6', we must distinguish two cases. 



When the vapour is represented by q^, then we have y — /? >0 

 and y- y./^Q. As y — ft^y—y^^ the denominators of (Ji) 

 and (14) ha\e either the same sign or the denominator of (IJ) is 

 positive, while that of (14) is negative. In each of these three cases 

 we find (/'«c^tp; the liquid-curve of the region L — G and the 

 saturationcurve under a constant pressure of 7^ are, therefore, situated 

 in the vicinity of point q with respect to one another as the curves 

 qp and qq\. 



When the vapour corresponding with li(juid q is represented by 

 q^, then y — l^ <^0 and // — y, >0; in absolute value (// — /:?) .y is 

 always smaller than (// y^)s. The denominators of (11) and (14) 

 have, therefoi'e, either the same sign or the denominator of (11) is 

 negative, wiiile that of (14) is positive. In each of these three cases 

 we find '/O^ V^ the liquid-curve of the region L — G and the 

 saturationcurve under a constant pressure of i^ are, therefore, situated 

 in the vicinity of point q with respect to one another as the curves 

 qp and qq;^. 



With the aid of the preceding considerations we may easily deduce 

 now the saturationcurves under their own vapour-pressure of F ; 

 for this we shall assume that the solid substance melts with increase 

 of volume. We distinguish three cases. 



1. The temperature is lower than the point of maximum-subli- 

 mation Tk of the binary substance F. 



In a similar way as we have deduced the general case fig. 11 (1) 

 we now find with the aid of fig. 1 for the saturationcurve under 

 its own vapourpressure a diagram as is drawn in fig. 2 ; in this 

 figure a part only of the componenttriangle is drawn. Curve 

 h a c in h n is the saturationcurve under its own vapourpressure, 

 /*! a^ c, F^ />i n^ is the corresponding straight vapourline. In this 

 figure are indicated the equilibria: F -\- Ln -\- Gh^, F -\- J^a -\- Ga^, 

 ^H-^c+ ^n> 1^^ A« + Gn., F^ U^Gö, and F -{- L„ -}-G„,; L,, 

 and Ln are binary liquids. As we have assumed that the temperature 

 is lower than the point of maximum-sublimation 2\ of the solid 



