295 
That for the Helium group, where the molecules also consist of 
only one atom, only the ordinary rest attraction asserts itself, and 
not the so much greater valence-attractions, is owing to this that 
the noble gases mentioned are valenceless. 
Clarens, May 1916. 
Physics. — “On the Fundamental Values of the Quantities b and 
Va for Different Elements, in Connection with the Periodic 
System. IV. The Elements of the Halogen- Oxygen- and Nitrogen 
Groups.’ By Dr. J. J. van Laar. (Communicated by Prof. 
H. A. Lorentz.) 
(Communicated in the meeting of June 24, 1916). 
I. The Halogen Group. 
After the treatment of the valenceless eighth group of the periodic 
system, i.e. of the group of the noble gases (to which we have 
added the hydrogen for convenience, sake) *), we shall now discuss 
the seventh group, that of the Halogens. We remind the reader that 
our chief aim is now to determine the values of War of the elements 
themselves, independent of the values calculated before in I and II*) 
from their compounds. 
a. Fluor. The critical temperature is unknown; I find some- 
where stated — 170°C. = 108° abs., but this cannot possibly be 
true, as the boiling point temperature lies already at — 187°C. = 
— 86° abs. according to Morssan and Dewar (1903). Now for the 
Halogens tlie ratio 7: 7; (Cf. the table in Il on p. 18) is resp. 
1,79 for I, 1,73 for Br,, and 1,75 for Cl,. If, therefore, for FE, we 
also assume 1,75 for it, 7} would become -= 151° abs. To this 
corresponds 2y = 1+ 0,088)/151 = 1 467, hence y= 0,733. If, 
therefore, the triple point temperature lies at — 223°C. = 50° abs. 
(Moissan and Dewar, 1908)”, then m, = 50: 151 = 0,331, and the 
factor f, = be: v, becomes: 
0,733 jn 
f, = 1,467 |! — =" x 0,831 | = 1,467 (1—0,140) = 1,262. 
Hence to find bp—55.10 5 for 1 Gr. atom Fluor, the atomic 
volume at the triple point must be = (55: 15362) 10 = 45,6. 10-9: 
Now for — 200°C. Moissan and Dewar (1897) found D= 1,14, 
‘ly See HI, These Proc. p. 287. 
2) These Proc. of Jan. 29 and March 25, 1916; p. 1228 and 2. 
3) In the “Chemisch Jaarboekje” for 1915-1916, I find — 283° C, given. 
