541 



region, when (lie liqnidciirve ed of the lieterogeneous region tonohes 

 the salurationcurve of F' . 



In the latter case, therefore, there is a series of pressures under which 

 at the same time two liquids saturated with F and two with F' 

 may be in equilibrium with vapour. Solutions saturated with F-{-F' 

 do not exist. 



When both the liquidcurves intersect each other numberless cases 

 are to be distinguished, of which we shall only discuss a few. 

 Imagining for instance in fig. 3 (I) that the vapoursaturation curve 

 of F' is also drawn, then we can obtain a diagram as fig. 1. The 

 liquidline d-e of the heterogeneous region intersects the saturation- 

 curve of F in a and b and that 

 of F' in.?; and ?/; the vapourcurve 

 of the heterogeneous region inter- 

 sects the vapoursaturationcurve 

 of F in a^ and b^ and that ofi^' 

 in x\^wéy^. The saturationcurves 

 of F and of F' intersect each 

 other in u and z. 



At the temperature and under the 

 pressure to which figure 1 applies, 

 therefore, besides the solutions satu- 

 rated with solid ^of branch bu and 

 az and the solutions saturated with 

 solid F' of branch xu and yz, there 

 still exist also the two solutions 

 u and z, saturated with F -\- F' . 

 The liquids of branch dx may be in equilibrium with the vapours 

 of f/i j\ ; the liquids of // a with the vapours of y^ a, ; the liquids 

 of be with the vapours of b^e,. The -solid phase i^ can exist together 

 with the vapours of branch a, b, ; the solid phase F' together with 

 the vapours of branch .^i y^. 



Further there are four liquids satuialed with a solid phase which 

 may be at the same time in equilibrium with a vapour. Therefore, 

 there exist four threephasecomplexes : solid -|- liquid -j- vapour, nl. 

 i^+ liquid r« -[- vapour a^, F -{- liqiud /> -f vapour b^, i^' -f liquid 

 .!• -f vapour .j'j, and 7^' -|- liquid // -)- xapour y,. Besides the great 

 liquidregion, indicated by L we find also in the figure the small 

 liquidregion a z y. 



On decrease of pressure figure 1 may pass now into figure 2. 

 The points a, y, and z of figui'e 1 coincide in figure 2 in the point 

 ƒ, the points a^, and y^ of lig. 1 coincide in fig. 2 in the point f^. 



35* 



Fig. 1. 



