PHYSICS: M. C. SHIELDS 
503 
or the Van der Waals equation of state (cf. Partington^). The final 
value 1.4029, is in close accordance with the three values which have 
been obtained by this method in carboys of 60 to 100 liters: Lummer 
and Pringsheim; 1.4025; Moody^ 1.4003; Partington,^ 1.4032. (Moody's 
published value has been revised by the addition of the internal work 
correction and by the removal of the applied radiation correction since 
it was already included in the intercept.) 
Data showing the same degree of uniformity were obtained in hydro- 
gen with four different junctions, in two cases the same junctions as were 
tested in air. These gave respectively 
1.4013, 1.4006, 1.4013, and 1.4017. 
There being no theoretical correction in the case of hydrogen, the 
final value is 1.4012. This value, so closely, in accord with the kinetic 
theory, is contrary to the only previous evidence of weight, viz., 1.4084, 
the original determination by Lummer and Pringsheim, and 1.407 com- 
puted by Scheel and Heuse^ from observations on Cp, which point to 
a quantum effect in hydrogen even at 18°. 
The development of ihe method in a one liter flask opened the possi- 
bility of observation with a liquid air bath, at a temperature where 
determinations by Scheel and Heuse on Cp and by Eucken^ on Cv 
have shown hydrogen to be virtually monatomic. By introducing a 
second low resistance potentiometer into the thermo junction circuit, 
it was found possible to make the thermometric arrangement quite as 
sensitive at -190° as at 18°, in spite of the fact that the thermal E.M.F. 
per degree is only about half as great. Observations are necessarily 
less precise because of the comparatively rapid change in temperature 
of the bath and the attendant difficulty in duplicating pressures. The 
final value of 7 with the correction for departure from the ideal gas 
state added, 1.592 at a mean temperature of 82° A., is however probably 
correct to 0.005, and corroborates closely the work of Scheel and Heuse. 
A full account of the work will appear in the Physical Review. 
1 Lummer and Pringsheim, Ann. Physik, Leipzig, 64, (536). 
2 Moody, Physic. Rev., Ithaca, 34, (275). 
3 Partington, Physik. Zs., Leipzig, 14, (969). 
4 Scheel and Heuse, Am. Physik, Leipzig, 40, (473). 
BEucken, Berlin, Sitz Ber. Ak. Wiss., 1912, (141). 
