( 278 ) 



VIII, ,t = 0.114 



T L ph. endc. ph. 



29°.9 69.15 pl.p. 69.15 pl.p. 



31 .2 71.20 2 and 3 74.10 „ 



32 .9 73.65 2 and 3 80.05 „ 



34 .6 76.65 2 and 3 85,90 „ 



35 .9 78.60—78.65 2 and 3 90.50 ? 

 37 .4 81.60-81.65 2 and 3 95.95 

 38.9 84.15—84.20 2 and 3 100.90 



39 .9 86.60 pip. 104.40 



41 .0 108.20 



42 .0 111.10 



43 .0 114.10 



44 .0 117.10 



44 .7 119.20 



45 .4 122.75 



46 .2 124.15 



tube bni'st 



Physics. — ''The vanahilitij of the quantiti/ h in van der Waals' 

 equation of stite, aUo in connection with the critical quantities." 

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



1. At the end of my last paper on the solid state (These Proc, 

 ]May, 1911) I annonnced on p. 100 the fuller discussion of the 

 problem alluded to in §§ 35 and 36. I may now be allowed to discuss 

 this problem more at length. 



In the paragraphs mentioned, particnlarly in § 35, I have already 

 set forth at length how we can arrive at a complete theory of the 

 variability of the quantity h, if we only assume that the molecules 

 are associated to larger molecule complexes to an amount varying 

 with the temperature and the volume, in which we must suppose 

 the volumes of the complex molecules smaller than the corresponding 

 volumes of the simple molecules which form the complex. 



I think I have demonstrated (loc. cit.) in a convincing way that 

 Ihe two causes of the variability of h, which were kept separate 

 before, are solved in, and are comprised by the wider theory of 

 association — which naturally also includes the third cause recently 

 brought forward by van der Waals — I mean the so-called "qnasi"- 

 association. 



For the diminution of the molecular volume h in consequence of 



