644 



§ 5. Hifdro(/en. Values of B for a diatomic gas in the tempe- 

 rature region for wliieli the terms given in (18) and (20) are sufficient 

 are onlj known as yet for lijdrogen. For this substance in view 

 of its small molecular weight one has to pay particular attention 

 to a possible modification of the molecular translational motion 

 according to the cpiantum tlieory. According to it a correction 

 ought to be applied to the values of pv, before the equation of state 

 in the form (J) would be applicable. As that correction depends 

 on other powers of v than occur in the second member of (1), a 

 conclusion about that intbience might be drawn for the temperature 

 region to be considered here from the agreement or disagi'eement 

 between the values of B calculated according to (1) without a 

 quantum-correction from measurements at higher pressures and from 

 such at densities near the normal one. The available experimental 

 material '), however, does not yet enable us to apply this test. 

 Meanwhile as mentioned abo\e we will disregard a possible influence 

 for the temperature region under consideration. We shall also leave 

 out of account the possible influence on the value of the second 

 virial coefficient of those deviations from ihe equipartition laws, 

 which according to ICucken's measurements of the specific heat are 

 shown by the rotations about the axes at right angles to the line 

 joining the atomic centres, at least in the lowest part of the tem- 

 perature region under consideration. 



In Suppl. N°. 25 (Sept. '12) it was shown that the dependence of 

 B on the temperature for temperatures above — 100° C. agrees 

 with that which' was derived for spherical molecules carrying a 

 doublet. From the agreement found in § 4 between the latter and 

 that for spherical molecules carrying a (juadruplet in the temperature 

 region specified there it follows immediately that the values of B 

 for hydrogen in the temperature region under consideration ought 

 to be found in agreement with the dependence on temperature which 

 we derived for quadruplets. 



To test this B/Binv for hydi'ogen was represented in a diagram as 



a function of T/2)nv(o = o) and compared with the v'alues calculated 



from (20) and (21) respectively. The values of B for hydrogen at 



—140°, —104°, 0' and 100° C. were taken from K.ameri,in(;h Onnes 



and Braak '), that for B at 20° C. from Schalkwijk ') and from 



Kamerlingh Onnes, Crommelin and Miss Smid ■•). The temperature of 



1) Cf. W. J. Haas, Gomm. N». 127a (April 12) § I. 



-) H. Kamerlingh Onnes and G. Braak, Comm N". 100 a and b (Nov. '07). 

 3) J. C. Schalkwijk. Thesis Amsterdam 1902. p. 1 Hi, alsoLeideuComm.N". T8p.22. 

 ■••) H. Kamerlingh Onnes, G. A. Crommelin and Miss E. J. Smid. Comm. N". 

 \W) (June '15). 



