( ^^ ) 



become clear to me. Tlie grounds alleged by van dkr Waals for 

 this p. 119 — 120, have not been able to convince mo and at. any 

 rate the supposition k=^l^ is arbitrary. It might be asked with 

 some justice how great the value of ii will have to be for contrac- 

 tion to take place in the molecular attraction, and below what this 

 contrciction need not be reckoned with (e.g. for ii=z2, see p. 119 

 loc. cit. : "It is true") In any case the futui'c will show whether, and 

 if so in how far a change should be made also in the value of 

 a — also with regard to the solid state. For there is reason to 

 assume that — in consequence of the immol)ility of the molecule 

 groups — the molecular attraction in the solid state may be different 

 from that in the liquid state. 



35. In conclusion I will still discuss here an important question, 

 which is in close connection with the foregoing, and which I thought 

 about already years ago: 1 refer to the dependence of the quantity 

 h on the temperature and the volume. 



In a third paper van dkr Waat,s once more discusses the critical 



quantities fully, and the changes to which they are subjected in 



consequence of the variability of b with v. The intluence of the 



temperature is disregarded in this important investigation. I also 



occupied myself with these questions already before — though it be 



on a more moderate scale — and handled the question in a perfectly 



analogous way. I need only refer to an article in the Arch. Teyler 



of 1901 ^), where I derived the cpiite general formula for Vc as a 



, fclb\ ,, fd'b\ 



function of 0^ —=/>,. and — =r b\ (see p. 2), and also that 



\dvjc \dv 'J,. 



ÏOY X^c, RT„ and f t = -^ (p. 7 formulae (9), (lOj and (11)). But 



particularly to a paper in the same Archives of 1905 : (c^uelques 

 remarques sur l'équation d'état, where on p. 47 et seq. I gave analogous 

 considerations to those van der Waals gave later on p. 117 — 119 

 of his tirst paper (June 1910) on the Quasi association, and more 

 extensively in his last paper of April 1911 (p. 1211 et seq.)*). 



Two things have particularly struck me in this last paper. First 

 of all that on p. J 214 with too great modesty van der Waals calls 



his theoretical formula log-^^zfl-^ 1 I an einuiricdl formula. 



' P V 2 J 



1) Sur I'influence des corrections a la grandeur /; etc. 



~) The formula (II) un p. I!ül4 for Vc agrees with llial already cited on p. 2 

 of my paper of 1901. 



