( 447 ) 



admixture; of eonrso only in so far as willi sufficient approximation tlio 

 conditions aw salislicd on wliich (he dri'i\alion of the e(jii;ilion (1) 



of VAN DEH WaAI.S rcsts. 



2. The answer to (his (piosdon is üivon in the uraphical I'opre- 

 sen(a(ion of li<»;. 2. It appears, namely, (h;if (he case which will dccni-. 



■"- - l^'-2 



is exclnsivelv determined bv (he rpiantities — = x and — =: y, which 



liave already played a prominent part in my above men(i(»ne(l 

 " T/u'orie f/eiK'rtt/c dcs pïis." 



In accordance with this a x- and a y-axis arc assnmed in {\<^. 2 

 of the plate and the regions where the points are situated whose x- 

 and y- values f^ive rise to the appearance of each of these cases, are 

 distinguished i)y diffei-ent numbers and colours. 



For instance the white region i indicates the x- and y- val nes for 

 wliich the plaitpoint enters the ip-snrface at I'ising temperature, moving 

 from K to the side of the large volumes, while in the well-known 

 way we can derive from its situation on the connodal curve on the 

 right above the critical point of contact R (for which the tangent 

 to the connodal curve runs parallel with the ^?-axis) that the retrograde 

 condensation will be eventually of the second kind (i. c. with tem- 

 porary formation of vapour) and also tliat the tem[)orary vapour 

 phase will have a larger amount of admixture than the permanent 

 denser phase. 



In the same way the blue tield 5 indicates the x- and the y-values 

 lor which the plaitpoint enters the ifj-surface at decrease of temperature, 

 moving towards the side of th.e large volumes; whilst the retrograde 

 condensation will be of the first kind and the temporary denser phase 

 will show a smaller proportion of admixture than the permanent 

 vapour phase. 



3. When examining this graphical I'epresentation we see at once 

 that one of the eight regions which were a priori to be expected, region 8, 

 fails. From this follows that for normal substances the combination 

 of retrograde condensation of the second kind and of a plait[)oint 

 which enters the surface at decreasing temperature and moves towards 

 the side of the small volumes, is not to be expected. 



All the other seven regions, however, are represented in the graphical 

 representation. 



4. Further the point x:=l,yzr=l, is i'emarkal)Ie, where no less 

 than six I'egions meet. This point represents really a xery particular 



