808 



phenomenon which is common knowledge now-a-dajs (and which 

 is mentioned even in elementary textbooks) was given by me 15 

 years ago ^) and that I myself and my collaborators made nse of 

 it in our recent researches on the allotropy of bismuth, cadmium, 

 copper and zinc. 



The quotation reproduced above is so striking that discussion of 

 the other instances of the same kind is unnecessary. 



T have always intended to abstain from any remarks on this point. 

 But as many colleagues both at home and abroad have taken 

 increasing umbrage at the procedure of Mr. A. Smits, I feel myself 

 reluctantly compelled to draw atttention to the matter. 



Utrecht, van 't HoFF-Laboratory. 

 January 1914. 



Physics. — "A new relation between the critical quantities, and on 

 the unity of all the substances in their thermic behaviour." 

 By J. J. VAN Laar. (Communicated by Prof. H. A. Lorentz). 



(Communicated in the meeting of January 31, 1914). 



1. In my latest paper '") I have treated some relations — also 

 derived by van der Waals — in which a perfectly accurate form 

 was substituted for the approximate one ; 1 have proved that not 

 any factor 6 =i f\v) by the side of "/t,2, so not the factor (1 — Va'^')% 

 added to it on account of the so-called quasi-association either, is 



able to account for the course of the function «/ =:' . '- in 



/I— 1 d^d^ 



the neighbourhood of the critical temperature (§ 3) ; 1 think I have 



demonstrated that either a, or b, or both must be functions of the 



temperature (§ 4), and I have made a few more remarks about the 



form of the reduced equation of state (,§ 5). Now I wish to make 



some remarks on the form of the dependence of the quantity b of 



the volume v. 



The temperature dependence will be considered in a subsequent 



paper. I may, however, state already now that I have come to the 



conclusion that this dependence too must be exclusively looked for in /;, 



whereas a is assumed to be independent of the temperature. Van 



DEK Waals seems finally also to have come to this conclusion, at 



1) Zeitschr. f. physik. Ghem. 30, 6i23 (1899). 



2) These Proc. of Sept. 3, 1913, p. 44-5'J. 



