180 



the pressure in fif>'. 2 must rlecrease from ri alonfj; tlie satiiration- 

 eurve, wliicli is in accordance with fig. 2. 



In the point n of figure 3 is AF, >0, /'/ — //<^Oand/:? — y,^0; 

 from (31) follows, therefore dP^O. Consequently the pressure 

 must increase from the point n in fig. 3 along the saturationcurve. 

 which is in accoi'dance with fig. 3. 



In the |)üiut n of curve 5 iu fig. 4 is A T, <^ 0, ,•' — // > and 

 /?— //i>0; from (31) follows, therefore <IPy>(). Consequently 

 the pressure must increase from n along ciii-ve 5, which is in 

 accordance with the direction of the arrows. 



We may summarise the above-mentioned results also in the 

 following waj' : when to the binary equilibrium 7^^-[-L-|-6r (in which 

 F is a compound of two volatile components) at a constant tempera- 

 ture we add a substance, which is not volatile, then the pi-essure 

 increases when the binary ecpiilibrium is between the point of 

 maximnm-sublimation Tk and the point of maximum temperature 

 T/i; in ail other cases the pressure decreases. 



In the consideration of the general case, that the vapour contains 

 the three components (XI and XII) we have deduced that the 

 saturationcurves under their own xapourpressure can disappear in 

 two svays at increase of pressure. 



1. The saturationcurve of the temperature 7// disappears in the 

 point H on the side BC [fig. 5 (XI)]. 



2. The saturationcui've of the temperature J"// touches the side ^C 

 in the point B and is further situated within the triangle ; at further 

 increase of T it forms a closed curve situated within the triangle, 

 which disappears at T/i in a point within the triangle [fig. 6 (XI)1. 



In the case now under consideration, that the vapour consists only 

 of B and Cf only the case 1 occurs ; this has already been discussed 

 above and is represented in fig. 4. It follows already immediately 

 from the following that the case 2 cannot occur. On a closed 

 saturationcul-ve under its own vapourpressure a point of maximum- 

 and a point of minimumpressure occurs. On the curves now under 

 consideration only, as we saw before, a point of minimumpressure 

 can occur, so that closed saluralioncur\^es are impossible. 



We may deduce this also in the following wtiy and we may 

 prove at the same time these curves, just as in the general case, to 

 be parabolas in the vicinity of H. 



When we consider the bijuxry equilibrium F -{- liquid H -\- 

 vapour, then ,; =0; we equate y = t/o, y^ =/A-ü and the pressure 

 =r Bn- To this equilibrium applies: 



