426 
sponds to the lowest observed argon temperature) corresponds to 
that of a monatomic substance *)’). 
e. In Nr. 88 of Suppl. N°. 23 hydrogen is compared with helium. 
From fig. 15 of that Suppl. it is evident that from the Boyre point 
downwards good correspondence is obtained between He and H, in 
so far as any conclusion is possible from the small number of helium 
points which were available for the construction of that particular 
branch of the log B, log Z-eurve®). To the figure just quoted we 
may now add the helium point 4°,29 K. from Comm. N°. 119 
(March 1914) § 5, which, in that figure, comes above the argon- 
hydrogen line. A suitable displacement *), however, of the helium 
diagram brings this point (whose degree of accuracy, however, is 
not so high as that of the points forming the H,-A-curve), too, on 
to the hydrogen-argon curve. 
From fig. 16 of Suppl. N°. 23 one can see further that, when 
superposing the hydrogen and helium curves so that the branches 
below the Borre point coincide, those above the Borre point deviate 
markedly from each other, from the figure quoted and from the 
table referring to it in note 399, that coincidence between the 
branches above the Boyrr point can be obtained only over a very 
limited region‘). So that at these higher temperatures appreciable 
deviations from correspondence between He and H, exist. 
1) The preliminary values of By obtained for helium in the corresponding region 
do not conflict with the suspicion that this is the case down to much lower 
temperatures (see €). 
2) From the data given on p. 425 note 3 for the displacement necessary to 
obtain coincidence between the A-curve and the H,-curve, and from the value 
T; = 150.65 for argon (C. A. GRoMMELIN, Comm. NO. 115, May 1910), we can 
calculate Pira, =°9,29 for the critical reduction temperature for hydrogen 
with respect ‘to argon as standard for comparison (cf. Suppl. No. 23, Nr. 380). 
Comparison with the critical temperature for hydrogen on the one side, with 
Tx (y:No, 0) 43 (Suppl. No. 23 note 399) on the other side leads to the con- 
clusion that the virial coefficients for hydrogen and argon higher than the second 
do not correspond perfectly, though the deviation from correspondence between 
the two substances within the region of temperature under consideration is much 
smaller than that between H, and Ng or Os. 
3) The third virial coefficient, C, then corresponds as well (see fig. quoted). In 
good agreement with this is the finding of a constant value for Tyr (He: Ho, At 
the points te =— 253° and — 259°, which does not differ much from 7, re 
(Suppl. No. 23 note 399). 
4) In this there is no longer any notice taken of the correspondence between 
the C coefficients, as is also the case in the other diagrams discussed in the 
present paper. 
5) Comparison with fig. 15 shows that the third virial coefficient, C, would then 
exhibit wide deviations from correspondence. 
