( 738 ) 



In fig. 7 T is thought higher 

 than the temperature at which 



= vanishes, and in fig. 8 



dx* 



below this temperature. In fig. 7 

 all the «/-lines have the very simple 

 course which we previously in- 

 dicated for them, and the p-lines 

 the well-known course, with which 



f — ) is positive on the liquid side 

 \dxj p 



dp n , . . . 



of — = 0, and on the vapour side 

 dv 



dp 

 of — = 0, negative between the 

 dv 



two branches of this curve, the 



fdv\ 

 transition of — from positive to 

 \dxj p 



negative taking place through 



infinitely large. The isobars p lt />, and p 3 have been indicated 



in the figure, in which p l <^ p^ <[ p s . Also a few (/-lines, q x < q, 



and the points of contact of p l to q x and of p 3 to g 2 . Also on 



the vapour side a point of contact of p z to q x . It is clear 1 st 



that every (/-line yields two points for the spinodal curve, and 



2 nd that these points of contact lie outside the region in which 



dp 



— is positive. On the other hand we see that the distance from 



dv 



dv 

 the spinodal curve to the curve — = can be nowhere very large. 



Only by drawing very accurately it can be made evident that on 

 the vapour side the spinodal curve lias always a somewhat larger 



dp 



volume than the vapour branch of the curve - =0. In the four 



Fig. 7. 



dv 



dp 



points, in which — = intersects the sides, indeed, the spinodal 

 dv 



line coincides with this curve. 



Fig. lb has been drawn to give an insight into the circumstances 

 at the plaitpoint. At 7 7 >(7 7 / l ,) 3 the two branches of the curve 

 dp 

 dv 



= have united at that value of a:, for which T = (Tk) x . One 



of the ^-lines, namely that of the value p — (pk)i, touches in the 



