645 



horizontal row of the' periodic system towards the right is 15 units, 

 in every vertical row the increase downward 55 uniL'. The elements 

 of the valence-less Helium group evidently fil in with the elements 

 of the pi'eceding Halogen group in a natural way. 



In this Helium group the values of bk are directly calculated from 

 those of 7\ and pk; also the value 59 for H from that of H, ^). 

 The other values have been calculated from the compounds of the 

 different elements (for CI the value 115 seems to be more satisfactory 

 than 110). From 7a- and pk we can directly calculate for N, P, 0, CI 

 from N„P„0, and CI,: 6 = 86, 135, 71 and 113 to 125 (according 

 as for CI, the data of Dewak or the more recent ones of Pkli.aton 

 are used). 



All the values of b can now be built up additively by the aid of 

 these fundamental values for the most divergent compounds. In this 

 also the "condensed" values 34 and 14 aie valid for H ; for C, N, 

 and the condensed values 75, resp. 60 and 50. The rules holding 

 for this are found in the two cited principal papers of 1916 in These 

 Proceedings and in the Journ. de Ch. Ph. 



No exceptions have been found to this additive law, those that 

 still existed for a few organic substances (e.g. the amines) have now 

 all disappeared, owing to the later determinations of T^ and /;^. by 

 Berthoud ') at Neuchatel, undertaken expressly in connection with 

 these deviations. The critical pressures determined earlier by Vincent 

 and Chappuis appeared to be all faulty to a high degree *). It is to 

 be foreseen that this will also be the case with other earlier 

 determinations. 



We will also state that the values of b for H, Li, Na, K, Rb 

 and Cs are to each other in the ratio Vi = 17* ■ ^Vs = 4:5:6. 



The values of b found are entirely independent oï{\\e^l?i{e,\nw\nQ\\ 

 the atom is: whether as free atom e.g. in metallic tin, or as part 

 of a molecule as in SnCl^. It will presently appear that this is not 

 the case with the fundamental values of V^a. 



2. F'or the values of 10' y-'ajc per Gr. atom, again expressed in 

 "normal" units, were found up to now the values recorded in table 



^) Of course the latest data were used for this ; for Hj and Ne the values found 

 very recently by K. Onnes, Crommelin and Cath. 



2) Journ. de Ghim. Phys. 15, 3 (1917). 



^) Thus p^ appeared to be = 55,5 for NHj.G^Hg, whereas V. and Ch. found 

 66; for NHiCgHj), the value 36.6 was found, against 40 by V. and Ch.; etc. 

 Also for C3H7CI Berthoud found 45,2, whereas V. and Ch. found 49. Errors 

 therefore from 10 to 20%! 



