( 134 | 
There are some cases that are less favourable, but considering the 
agreement with the isothermals which are represented by the system 
of co-efficients, Ba, Ca, Da, Ha, Fa, the regular course of these 
co-efficients with the temperature may be adduced as a proof that 
the co-efficients obtained have not only importance for the calcula- 
tions but have also a physical meaning. Even if some difficulties 
remain as with the densities of carbon dioxide at pressures above 
850 atm. and with the densities in the neighbourhood of saturation, 
the choice of six terms in the polynomial appears in reasonably 
good agreement with the nature of the probiem and the accuracy 
of the observations. 
§ 4. In order to express the virial co-efficients as functions of 
temperature we introduce the reduced quantities: 
p v tie 
p a ’ » rn ? t = ry (8) 
Pk Ul Fi 
where Z relates to the critical state. 
Then (I) changes into: 
5 ¢ D E y 
AY o = Y — Nn ——. Ill 
‘ a Ay» 15 A? pv? zE At yt Àö yo +r 18 ps Ce 
where U, B, €, D, € and § are functions of t and 
Pk UI: 
A= eee, =. RD 
Aly ( ) 
while 
A B C 
MES DES —— », ©&= pm? 
(10) 
Altes Eik F | 
SNS ’ SS Er —— MJ 
