( 743 ) 



ordinary plait, which portion will then on the whole run in the 

 direction of the /--axis. 



There remains an important question to be answered: "What 

 happens to the spinodal curve and to the plaitpoints with increase 

 of temperature?" 



At the temperature somewhat higher than (TV), there exist 3 

 plaitpoints in the diagram. 1. The realisable one on the side of the 

 liquid volumes. 2. The hidden plaitpoini also on the side of the 

 liquid volumes. 3. The realisable vapour-liquid plaitpoini. Let us 

 call them successively I\, P, and P s . Now there are two possibilities, 

 viz. 1. that with rise of the temperature I\ and P s approach each 

 other and coincide, and the plait has resumed its simple shape before 

 P 3 disappears at T=( k 7%\; and 2. that with rise of T the points 

 I\ and P 3 coincide and disappear, and also in that case the plail 

 has resumed a simple shape. In the latter ease, however, the plait- 

 point is to be expected at very small volumes, and so also at very 

 high pressure. Then, too, all heterogeneous equilibria have disappeared 

 at T= {Tk) x . Perhaps there may be still a third possibility, viz. 



d 2 \p 

 when the locus — — = would disappear at a temperature higher 

 das* 



than {Tk) x . Besides the plaitpoint P l another new plaitpoint would 

 then make its appearance at T=(Tj c ) 1 on the side of the first com- 

 ponent. This would transform the plait into an entirely closed one, 



and only above the temperature, at which = vanishes, all he- 



dx* 



terogeneous equilibria would have disappeared. 



Let us now briefly discuss these different possibilities. We shall 



restrict ourselves to the description of what happens in those cases, 



and at least for the present leave the question unsettled on what 



properties of the two components it depends whether one thing or 



another takes place. If P 1 and P 2 coincide, the portion of the locus 



d> 



= which we have drawn in fig. 8 for smaller volumes than 



d*\p 

 that of ^rrr = 0, must have got entirely or almost entirely within 

 dv" 



the region where is negative in consequence of the rise of tem- 



dv* 



d' 2 ty 

 perature, or the whole locus -— • = may have disappeared with 



(ZtC 



rise of T. 



Now at P l in the previously given equation : 



