236 ) 



or 



'■•s/ -r- = (■'■.^— ''7") 



las tlic \;ilue of I ^^^ — 1 . as follows from llic ('(luatioii uiv(Mi if 



111 \\iï> way \\v sim|>lify the discii^sioii. Tlic factoi' of'./'., — .//liever 

 becomes iiifiiiifely great in tliis ease. Tlii> factor is tlieii jiositive 

 outside tlie spinodal curve and negative inside it. < )n the spinodal 

 curve it.self it is zero. As ,/,, — .ly^ is alwavs negatixe in the case of 

 antliracjuiiione and etiier, the second member of tlie hist e(|uation is 

 iiegati\'e outside the spinoih-d cuivc and po.-ilixe inside it. From this 

 last equation follows: l^Mhal if we fobow th(M*ontact-cnrve throughout 

 its course, fliere exists a maximum and a minimum value for tlie 

 ])ressnre for tlie points Iving inside the plait, that is aa hen the spinodal 



curve is passed. 2"*' that when r,,=z{). the value of — is either 



('Lr 



twice oi' onl\ once inlimtelx ureal. In llie i)oint> where = ^h 



dv/' 



dp ^ ^, , ^. f^/> 



d7r 



we put there ^^ — =<>, bul xxhich al.-^o follows directU from: 



dp = - d.Vf ^ ~ drj, 

 O.rf Off 



dp 



i)nttiim' ^^ ^ 0. 

 " Ovf 



For contact-cur\es which jiass through the plait not far from the 



plaitpoint. it ai»|)ears clearlv from the figure, that the points for 



(III . . '//' 



which — is iiithiiit'lv ureat. lie outside those for w Inch-— = 0. 



d.i' " ^ di'f 



That is to sav, that the locus for which Vgf =i 0, lies outside the 

 spinodal curve. In the neighbourhood of the top of the plait thev 

 lie e\en outside the connodal curve. Also for the isobar BElJl)' E' Ji' 

 I have drawn them in the figure gixeii in such a way that the 

 points of contact of tangents from l\ lie outside the spinodal ciii-xe. 

 I have not yet been able to decide whether there are any exce])tions. 

 In the following figure (3) I have re{)reseiifed the relation between 

 It and .I'f for a contact-curve, assuming tliat the points of contact 

 lie as I have <irawii them in fig. 2, and as they are sure to lie, 

 when we are in the neighbourhood of the plaitjxnnt. The gas phases 

 which are in equilibrium with the solid body lie below B. 



