THEORY OF VISCOSITY AND THERMAL CONDUCTION, IN A MONATOMIC GAS. 347 
<r in terms of /i. In this paper I shall give only a few values of <r, calculated from 
recent data and from the exact formula 
0-2 = (1 + e a) 
5 m 
64^ (1 + S/T) 
0*491 (1 + e „) P C 
2 Snm (l +S/T) 
appropriate to attracting spherical molecules. The values of S are determined from 
the variation of viscosity with temperature, C is the mean molecular velocity, while 
e u is found from Table VI. (in all the cases here considered it is quite negligible). 
In the following table values of the diameters calculated from the constant b of 
van der Waals’ law are also given for comparison. The agreement between the two 
sets of values is in most cases remarkable, and the table as a whole is a testimony to 
the close numerical accuracy now attained by the kinetic theory ; where there is 
disagreement in the table there is in most cases uncertainty as to the data. 
While exact agreement may be expected only for monatomic gases, the values for 
diatomic gases show that our theory gives a mean diameter, in other cases, which agrees 
with that found for b ; the internal energy which prevents the application of our 
formulae to the conductivity of polyatomic gases hardly affects viscosity. 
Table VIII.— Molecular Diameters Calculated from Viscosity and 
Van der Waals’ Law. 
Gas. 
o 
►—> 
O 
S. 
1 + « a - 
(Table V.) 
Van der Waals’ 
b. 
2ovl0 8 
(viscosity). 
2ov 10 8 
(Van derWaals.) 
Argon . 
2107 
162 
1-002 
0-001347 
2-84 
2-85 
Krypton .... 
2334 
182 
1-001 
0-001774 
3-12 
3-14 
Xenon . 
2107 
252 
1-000 
0-002304 
3-47 
3-42 
Helium. 
1885 
75 
1-006 
0-000432 
1-89 
1-96 
Oxygen .... 
1923 
130 
1-005 
— 
2-93 
2-89 
Hydrogen .... 
854 
76 
1-006 
0-00096 
2-36 
[2-52] 
Nitrogen .... 
1672 
112 
1-003 
0-00255 
3-10 
f 3‘54 
\3-08 
Air. 
1721 
111 
1-004 
0-00209 
3-08 
3-30 
Carbon dioxide . . 
1388 
249 
1-000 
0-00228 
/ 3-27 
\ 3 • 20 
3-40 
3-20 
References. 
Viscosity /u 0 at 273° C. absolute .—These values are taken from the table onp. 476 of 
my first memoir, where full references may be found. They agree very well with the 
list given by Eucken (‘ Phys. Zeitschr.,’ 14, Table 3, 1913), in which Vogel’s 
determinations are included with other recent values in taking means. 
