Physics. — ''On the Heat of Dissociation of Di-atomic Gases in 

 Connection with the Increased Vahncy- Attractions \^A of the 

 Free Atoms". By Dr. J. .1. van Laar. (Commnnicated bv Prof. 



H. A. LORENTZ). 



(Communicated in the meeting of October 27, 1918). 



fntrocbcction. 



1. In a series of Treatises in these Proceedings ^ on the additivity 

 of the values of h and V'^a of the equation of state, and on the 

 fundamental values of these quantities for different elements in 

 connection with the periodic system, I determined the following- 

 values of b . 10^ Rud l^ a . \0^ , expressed in so-called "normal" units. 



The values of bk . 10* (per Gr. atom), determined up to now, are 

 found collected in Table I. 



TABLE I. (Values of bk . lOS). 



C = 100 N = 85 = 70 



(75) (60) (50) 



F = 55 



Si =155 P=144| S = 125 Cl=110 



èll5 



Pb = 320 Bi = 305 

 k315 



Th = 400 



He =105 

 Ne = 76 

 Ar =144 



Ti = 180 



Ge = 210 i As = 195 Se = 180 1 Br = 165 Kr = 177 

 Zr = 235 j I j 



Sn = 265 |Sb=250|Te = 235 I = 220 ' X = 228 

 Ce = 290 



Nt = 277 



It will be remembered that these fundamental values present a great 

 regularity. Starting from the carbon group the decrease in every 



1) These Proceed. 18, 1220 and 1235; 19, 2, 287 and 295 (1916); 20, 138, 

 492 and 505 (1917). Cf. also Journ. de Chim. Phys. 14, 3 (1916), and Zeitschr. 

 f. anorg. u. allg Ghem. 104, 56—156 (1918). 



