953 
; Op 
rieure ')), and of REINGANUM's a, ay = 7 (si) —p| v?, calculated 
as functions of the temperature and of the density from equation 
VII. A. 35. The temperature is expressed in Kervin degrees and 
is calculated from 0° C.; the pressure is expressed in international 
atmospheres *). 
The importance of a knowledge of these. quantities especially as 
functions of the temperature has already been repeatedly insisted 
upon‘) so that we need say nothing further here upon that point. 
We shall only say that according to the chief vaN per WAALS equation 
Op Ou 
with constant ay,O, and A, _ . (5*) and «ag should be inde- 
a ve OWA 
(0? p 
pendent of the temperature, and consequently ad should vanish, 
so that the deviations whieh they all show may be taken as a 
measure of the degree to which argon deviates from the simple 
assumptions regarding molecules accepted by Van per Waars in deve- 
loping his prineipal equation. 
Agreement, at least approximate, with the chief van per Waars 
equation would first be expected in the monatomic substances, and 
therefore the investigation of these quantities for argon as well asa 
comparison of the results with those for substances of more complex 
molecular structure is of the greatest importance. 
Consideration of the quantity introduced by Reincanum °*). 
Sada = Op - Ou 
eel), 
enables us to see that, as far as the mutual actions of the molecules 
_is concerned, the assumptions upon which van peR Waars founded 
his chief equation with constant ay ,6,,and Ry must undergo some 
modification such as has recently been introduced by vaN DER Waars in 
the various developments of the consideration of apparent association. If 
we retain for the moment the most immediate assumption suitable for 
monatomic substances such as argon, that the atoms are incompressible, 
then changes in ar would be wholly dufe to deviations of the molecular 
1) E. H. AMAGAT, numerous papers in the C. R. collected in “Notes sur la 
physique et la thermodynamique”. Paris 1912. 
2) For the notations used in this paper see Enc. math. Wiss. V. 10. Suppl. N°. 23. 
3) Enc. math. Wiss. V. 10. Einheiten. a. 
4) M. RernaanuM, Diss. Göttingen 1899, Ann. d. Phys. (4), 18 (1905) p. 1008, 
Suppl. N°. 23, p. 140 sqq. 
5) M Retneanum. Diss. Gottingen 1899, 
