425 
(Suppl. N°. 246 § 6), that we need only allow for electrostatic forces. ') 
Consideration of the viscosity lends some support to the result 
obtained above that hydrogen behaves at higher temperatures in the 
planetary gas state as a system of hard spheres of central symmetry, 
each with an electric doublet at its centre, but deviating considerably 
therefrom at lower temperatures. On this point we may refer to $ 6. 
d. Comparison of the log 5, log T-diagram for hydrogen with 
that for argon affords an important insight into the behaviour of H, 
below the Boyre point which is closely related to the deviation 
found in e for the H, diagram from that for constant doublets *). The 
individual virial coefficients for argon 
cr ee were taken from Comm. N°. 1185 
ra [O (Dec. 1910) by KAMERLINGH ONNEs and 
iy: a +—  Cromme.in. From their measurements a 
7 portion of the branch (n) of the log B, 
| © 5-10 log Z-curve lying below the Borre 
en point is accurately known. 
Z| B Een On superposing the log By, log 7- 
7 a curve for hydrogen on that for argon 
LON ew it is evident that the latter quite well 
12 J ae fits the corresponding part of the hy- 
Re drogen curve, see Fig. 3°). 
4 Oo From this it follows that, in so far 
[as OO hydrogen Bis as the second virial coefficient of the 
684 AA Agen Ee thermal equation of state is concerned, 
UBS oe fa a the thermal behaviour of hydrogen from 
19 av — 180° U. to at least —- 230° C. (the 
Fig. 3. temperature for hydrogen which corre- 
1) The length of the axis of a doublet may also be neglected in a first approx- 
imation, as has always been done here. In a more accurate calculation, however, 
this would have to be allowed for. 
2) The deviations from the law of corresponding states occurring in B and C for 
hydrogen when compared with their values for other substances, such as oxygen, 
nitrogen, carbon dioxide, ether and isopentane, for which, as well as for hydrogen 
at very high reduced temperatures, the mean reduced equation VII.1 (Suppl. N°. 19, 
p. 18) holds, first found definite expression in the special equation VII.H,.3 
(Comm. N°. 109a equ. (16)), which was introduced for this purpose; marked diffe - 
rences occur between the ® and € of this special equation and those of the mean 
equation VII.1. The continuation of the investigation of the nature of these diffe- 
rences which was commenced in Suppl. N’. 23, Nr. 38, was left to me by Prof. 
KAMERLINGH ONNES. 
3) Then the point log 7 = 2,4, log By = 7,2—10 for argon coincided with the 
point log T= 1,869, log By = 6,908 for hydrogen. 
28 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
