{ 137 ) 



For llie present, hovv^ever, I leave these questioiiy and (lifificnlties 

 out of consideration, and 1 contine myself to showing that a for- 

 mula of tlie form (4) can really make the considerable ditrerences 

 disappear wliich \v(^ liavc met wilh till now. The more so as this 

 formula appears to be adapted for the derivation of general conse- 

 quences, which follow from the decrease of b with v. I leave there- 

 fore a possible de|)endcncy of />„ on 7'out of consideration. Moreover 

 ill ap[tlyiii,ü' the formula 1 will suppose h,/ = '2 />„. I choose one — 

 in some respect arbitrarily — from all the forms which 1 have found 

 to be possible (compare also my paper in the Arch. Xcerl. "Livre 

 Jub. dédié a Bosscha). The numerous calculations required in order 

 to investigate in how far modifications are necessary and possible 

 in order to make the agreement with the experiments more perfect, 

 may perhaps be performed later. 



A. llie tension of the saturated vapour. 



Let us begin \\\{\\ the calculation of the pressure of the saturated 

 vapour at low temperatures and let us to that purpose write the 

 equation expressiitg that the thermo-dynamic potential has the same 

 value in coexisting phases, in the following form : 



a rdiv-l)) rdb^ 



V J v-h J v-h_\^ 



of 



a rdb " 



^H- R T lor/ (v-h) -RT\ = 



V ' J v-l>_\^ 



In my paper "De kinetische beteekenis dei thermodynamische 

 potentiaal" I have already pointed out the signification of the tei-m 



r lib 



RT \ ; it represents namciv the amount of work performed by 



J v—h 



the kinetic pressure on the molecule when this [)asses in a reversible 



way from the condition of the first phase into that of the second 



phase and when its volume is therefore enlarged either fictitiously or 



as we now take it to be, really. We may calculate this term if we 



assume the chosen form for b and this is one of the reasons why 



I adhere to the idea of a real increase of the molecular volume. 



Hut though its value may depend upon the particular form which 



we have assumed for b, it will certainly have a positive value for 



every law of variability of b with v which we may choose. 



rdb , b-b^ 

 Let us for the calculation of | denote — by z, then we 



J 1^ — ^' 'V~"''tt 



