599 



J^-^L-\-G occurs, but tlie point p is not a point of maximum 

 pressure of the saturationcui-ve undei' its own vapourpressure (we 

 will refer to this hiter). 



On further decrease of pressure one or more points of intersection 

 are found, therefore also one or more threephasetriangles; the different 

 diagrams may be easily deduced in the same way as in communication I. 

 On further decrease of pressure we attain a pressure P,,^ under 

 which the contemplated curves have for the last timo a common 

 point ; we call this point m. P,a therefore is the lowest pressure 

 under which the system F -{- L-{- G can still occur and the points 

 F, m and the corresponding vapourpoint m.^ are situated again on a 

 straight line. When m is situated within the triangle, it is again a 

 point of contact and also a point of minimum pressure of the satu- 

 rationcurve under its own vapourpressure. When m is situated on 

 the side BC of the triangle, (we imagine in tig. 'J the liquid curve 

 of the region LG through the point (j) the two curves do not come 

 in contact with one another in q, and q is not a point of minimum 

 pressure of the saturation curve under its own vapourpressure. 

 Of course Pq is the lowest pressure under w^hicli the system P' -\- L -\- G 

 may yet occur. 



Now we will deduce some saturationcurves undei' their own 

 vapourpressure. 



T <^ 7 A- At tirst we choose a tempera- 

 ture T lower than the point of maximum 

 ^ib sublimation Tk of the binary compound F. 

 In a similar way as we have deduced fig. J 1 (I) 

 for the general case, we now find a diagram 

 as is drawn in fig. 2. In this figure however 

 only a part of the componenttriangle ABC 

 is drawn ; the line li^Fn is a part of the 

 side BC. Curve halm is the saturationcurve 

 under its own vapourpressure, h^ajj^n, the 

 corresponding vapourcurve ; we shall call 

 also here both the curves circumphased. 



Fia-. 2. 



At the deduction of this diagram we have 



assumed, that on these curves neither a point 

 of maximum- nor a point of minimum i)ressure occurs ; the pressure 

 increases from n to //, without being however in n a minimum and 

 in h a maximum. From the deduction it follows also that the sides 

 solid-liquid and solid-gas of the threephasetriangles must have a 

 position with respect to one another as is drawn in the triangles 

 Faa^ and Fbb,^. 



