88 
PROFESSOR W. RAMSAY AND DR. M. W. PRAYERS 
Hydrogen. 
Helium. 
Lithium. 
14-3 
2 
?(1D9) 
Nitrogen.* 
Oxygen.* 
Fluorine.* 
Neon. 
Sodium, t 
17-7 
14-1 
17-15 
? 
3DO (23-7) 
Phosphorus, t 
Sulphur, t 
Chlorine.* 
Argon. 
Potassium. 
20-9 (17-0) 
21 -G (15-7) 
23-5 
32-9 
?(45-4) 
Arsenic. 
Selenium. 
Bromine, t 
Krypton. 
Ruljidium. 
- (13-2) 
- ( 18 - 5 ) 
27-1 (26-9) 
37-8 
? (56-1) 
Antimony. 
Tellurium. 
Iodine.* 
Xenon. 
Caesium. 
- (17-9) 
- (20-3) 
34-2 (25-7) 
36-4 
?(70-6) 
The figures in l^rackets refer to atmospheric temperature, and are taken from 
C. Schmidt’s work. It is to be noticed, if tliese figures are mapped as ordinates against 
atomic weights as ahscissce, as shown by Lothar Meyer, tliat argon follows chlorine 
on the ascending branch, of which the highest member is potassium; that krypton 
occupies a regular position on the curve of which the members with lowest atomic 
volume are cobalt and nickel and tbe highest rubidium ; while the position of xenon 
is near that of iodine, and lies between it and cmsiinn. In short, the atomic volumes 
of these elements exhibit that partial regularity characteristic of all the others; and 
their place on the atoinic volume curve is a normal one. 
If it is permissible to speculate on the atomic volumes of helium and of neon by 
interpolation, they are respectively 13'5 and 20'2. This would make the densities 
of the liquids 0’30 and DO, approximately. These numbers would then complete tlie 
following series of densities :— 
Helium. Neon. Argon. Krypton. Xenon. 
0-3? DO? D212 2T55 3-52 
The whole table of atomic volumes, as far as that of cresium, is I'eproduced in the 
accompanying diagram. The ])eriodicity of the inactive elements is obvious. A word 
may lie said regarding the apparently abnormal position of argon ; with the atomic 
weight 40, there is a reversal of direction in passing from argon to })otassium, and 
from potassium to calcium ; but the same peculiaiit}" is observable with iodine and 
tellurium. While the diftei'ence lietween the atomic weio-ht of anv element and that 
C' %/ 
preceding it or succeeding it on the table is generally positive, although very 
irregular, it a])pears that a few instances of revei'sal cannot be ignored, and argon 
forms one of these. The peculiarity of the diagram, it must be noted, is due to the 
atomic weiglit of argon and not to its atomic volume. 
* ])ru(;man and Ramsay, ‘ Trans. Chem. 8oc.,’ vol. G7, p. 1228. 
t Ramsay, ilnd., yoI. 39, p. 472; Ramsay and Masson, ibid., vol. 39, p. 49; Thorpe, ibid., vol. 37, 
p. 391. 
