540 



reverse. In (ig. 4 the point F is situated within tiic rej^ion J.— (r\ 



of course it nui}- also be situated in the 

 liquid- or gasiegion. 



Further in tig. 4 the vapourcurve of 

 the region L — G intersects the saturation 

 curve of F ; however, it may also sur- 

 round this curve so that the saturation- 

 curve is situated completely within the 

 region L — (t. We shall confine ourselves 

 in the following to the case drawn in fig. 4. 



When on further increase of T the liquid curve of the region 

 L — G contracts now still more rapidly than the saturationcurve 

 of F, no new points of intersection make their appearance. 

 We have then obtained a boilingpointcurve of a simple form 

 with a minimum boilingpoint in m and a maximum boilingpoint 

 in M. It surrounds the point F and is itself surrounded by its 

 cori'esponding vapourcurve. 



We will assume however that the saturationcurve of F and the 

 liquidcurve of the region L — G move in the point M of fig. 4 

 with the same rapidity (further we shall see under what conditions 

 such a case is possible). While at a temperature somewhat lower 

 than Tm the saturationcurve of F moves in the vicinity of M more 

 slowly than the liquid curve of the .region L — G, at a temperature 

 somewhat higher than 7j/ this is just the reverse. 



Consequently on increase of 7'above Tm in the vicinity of the point Ji, 

 two points of intersection occur fagain), which shift towards the left on 

 further increase of 7' and finally coincide in a point Q. At this tempera- 

 ture Tn the saturationcurve of F and the liquid curve of the region 

 L — G touch one another again therefore in a point Q. However 

 the two curves are situated now completely outside each other. The 

 liquidregion therefore is now situated completely outside the saturation- 

 curve of F and not as at tlie temperature Tm (fig. 4) within this 

 ^ ^ ' "" " -^ ^ curve. On further increase of T 



^ N points of intersection occur no 



more. 



The boilingpointcurve will 

 now ha\'e a form as curve 

 niMQ in fig. 5 : it shows a 

 double |X)int in Af. The tem- 

 perature increases in the direc- 

 tion of the arrows , it is a 



■ .— ^— ^ minimum in m, a maximum in 



Fig. o. 



ft\. 



