750 



towards FE, its corresponding P,T-cnv\e must therefore change 

 from UKF into EHF. Now we shall examine this more in detail. 



The saturationcurves under their own vapourpressure have, in the 

 vicinity of H either a form as in fig. 5 (XI) or as in fig. 6 (XI) ; 

 we assume that they have a form as in tig. 5 (XI). In fig. 1 the curve 

 surrounded by Fs, and Fs, itself represent saturationcurves under 

 their own vapourpressure; the arrows indicate the direction of 

 increasing pressure. 



The boilingpoint curves have also a position as in fig. 5 (XI) ; 

 we must consider, however, that H is replaced by the point ot 

 maximumpressure Q and that the arrows point in opposite direc- 

 tion. Two of these curves are drawn in fig. 1, one in the vicinity 

 of Q and curve Fk; the latter is indicated for a part only. 



Now we imagine in fig. 1 a solutionpath between FE and FZ^y 

 Imagining in this figure still many other saturation-curves under 

 their ow i vapourpressure to be drawn, then we see that some of 

 these aro not intersected by this path, other ones twice, and others 

 again once. Further we see that one of these curves touches this 

 path; we call that point of contact H' . 



From this it follows: at tlrst the temperature increases along this 

 solutio; 'i from F up to H' and after that it decreases. Further 

 it follox.o: Th' is lower than Th- 



Imagining yet many other boilingpoint-curves to be drawn in 

 fig. 1, then we see that one of these touches the solutionpath in 

 a point that we shall call Q' . Now we deduce: the pressure in- 

 creases along this solutionpath from F up to Q' and after that it 

 decreases. Further it follows: Fq; is smaller than Pq. 



Now it follows from this all that the P,T-curve belonging to this 

 solutionpath has a form in fig. 2 as curve bF with a point of 

 maximumpressure in Q and a point of maximumtemperature in H' . 



As long as the solutionpath in fig. 1 is situated between FE and 

 FZ.^, the P, T-curves retain a form as bF in fig. 2; according as 

 the path, however, approaches closer to FZ^, the points Q' and H' 

 come closer to F. When the path coincides with FZ^, H' coincides 

 with F and the P, T'-curve has a form as Z^F in fig. 2 with a 

 point of maximumpressure Q" . The tangent in F stands vertically. 



To see this, it must be considered that the line FZ^ touches in 

 F the saturationcurve under its own vapourpressure going through P 

 {Fs in fig. 1). Going from P, along an infinitely small distance, along 

 curve Fs and therefore also along the tangent PZ^, the pressure 

 increases while the temperature remains constant. As dP, therefore, 

 is positive, and dT is zero, the P, P-curve therefore, in fig. 2, along 



