( 72 ) 



= 0, and also 



/d"p\ 



I — 1 = 0, and then the n-curve has the shape 



of fig. 18. 



For q above this value the spinodal curve is cut in 4 points. The 

 two new points of intersection lie then on the left and on the right 

 of 1\, and at the heginning in the neighbourhood of this point. Then 

 a portion lying in the stable region has been added to the g-line, 

 from which we derive that p is smaller in the point of intersection 

 lying on the right than that lying on the left. Not until now has 

 the />-line the shape of fig. JH, but the branch c is still very small 

 then, and the pressure of point 3 of this figure only little higher 

 than of point 2. From this moment there could be question of the 

 application of Maxwell's rule to the 5 branches a, b, c, d and e, 

 and so of the determination of the 12 points of the binodal curve. 

 But at the beginning not all these 12 points are real. The application 

 for the combination of the first and the last branch is certainly 

 feasible, and it yields a couple of realisable points for the binodal 

 curve, and in contradiction with our result when we treated this 

 combination for the q-Vme in fig. 17, the points defined in this way- 

 are not metastable but stable. No less is the application possible for 

 the combination {b, (I), and the two points determined then lie in the 

 unstable region, and can be represented by the points 4 of fig. 17, 

 provided they are shifted nearer the point /'.,. The rule cannot be 

 applied to the remaining 4 combinations. For the possibility of the 

 application to the combinations (a, c) it is required that the length 

 of branch c be such that the pressure of point 3 (fig. 19) be at least 



Fig. 19. 



positive; and even this is not sufficient. It', namely, we have from 

 point .'! a line // y-axis, and if then the area between the branches 



