( '^'9 ) 



(he increasing association, on diniinntioii oi' (he volume v e. g., can 

 be considered to be a real dinniinution of that molecular volume, but 

 also as an appareM diminution accompanying it. The quantity 

 ^h — — h^ -f r/>2 introduced in our theory need namely not necessarily 

 indicate exclusively the real change of the volume of a molecule, 

 but can also include the apparent change, in so far as it is manifested 

 in its elfect on the pressure in consequence of the temporary aggre- 

 gations of (he molecules (see p. 96 and 97 loc. cit.) ^). 



The degree of variability of h is then further exclusively determined 

 by (he degree of dissociation ,-? of the compound molecnle-conqd^xes. 

 As (his t|uanti(y beijig a function both of v and 1\ the <juantity b, 

 given by /> = (1 — /i) ij -(- i'/i6.^, i.e. by 



6 = r6, -(1 — /?) A6, 



will depend besides on v, also on T, though the latter will be the 

 case only to a very small degree, as we shall show presently. 



Ir is this way of considering the problem, which I dimly conceived 

 already some ten years ago, and winch I have practically never 

 quite abandoned, though 1 adopted other points of view for a time. 

 Now after the completion of my theory of the solid state, I am 

 more than evei' convinced that my original point of view must be 

 the right one. Already the course of the quantity /? as function of 

 V and T made me see the great probability of this point of view. 

 The way, namely, in which /5 for v and 7'= approaches asymp- 

 totically (so that only complex molecules are then present), and 

 approaches 1 asymptotically for v and 7^=: oc (all the molecules 

 sinqile) ; while the critical point appeared to lie exactly at the beginning 

 of the abrupt inlleetion from 1 to — which pointed to an appre- 



db 

 ciable value there of b =z — , and to a rather considerable value of 



dv 



d'b 

 — vb" =^ V — — all this convinced me more and more that the 



dv^ 



xariability of /-' was onli/ and e.vc/iisiveli/ to be attributed to the 

 varying degree of association of the molecules, together with the 

 variation of volume A6 (real or apparent) attending it. 



Whereas in ihe paper of van di<:r Waals presently to be mentioned 

 (loc. cit. p. J 227 and 1228), oidy an ernpirical relation could be 



^] Exactly in (lie same way as among olhers Reinganum, when lie comes to the 

 conclusion that the influence of the temperature on the pressure which tlie mole- 

 cules of a non-ide:il gas exert on the wall, is manifested in a fictitious enlarging of 

 the molecule: it seems '^as if' the molecules are enlarged with rise of tempera- 

 lure ; etc. 



