( 1019 ) 
a. By substituting values of argon vapour pressures in the well 
known VAN DER WAALS vapour pressure equation *) 
re, PT; 
log — = f — 
t Pk a 
and using common logarithms we get the following values for /: 
t p in atm. | 1p 
| =! | 
—140°.80C.) 22.185 2415 || 
| —4349.72C.| 99.964 2.491 | 
| AE 35.846 2.457 | 
—125°.49C,| 42.457 2.577 | 
A cursory comparison of these values of f with those for other 
substances shows us that the value for argon is closer to the theoretical 
value of f at the critical point deduced from van DER WaAALS’s 
equation (1.737) than the values belonging to by far the greater 
number of other substances; this is what one would expect for 
monatomic substances. For carbon dioxide between —63° C. and the 
critical point f goes from 2.84 to 2.977); for isopentane *) between 
130°C. and the critical point f assumes a value between 2.75 and 
2.95, while it further appears from the list published by KveNeN ‘) 
that, with the exception of monatomic substances and a few others 
such as hydrogen, oxygen, and carbon monoxide, values of f are 
always still greater. 
6. From the critical data already published, and from the weight 
in grams of one litre of argon at normal temperature and pressure 
which, according to Ramsay and Travers?) is 1.782, we found for 
the critical virial quotient 
Pkek 
This value is also closer to the theoretical value deduced from 
VAN DER Waars’s equation, 2.67, than those of almost all other 
') J. D. van pen Waats, Cont. I, p. 158. 
*) J. P. Kurnen, Die Zustandsgleichung, p. 101, supplemented by Krrsom’s 
measurements, Proc.Jan. 1904, Comm. NV. 88. 
3) S. Young Ì. c. 
4) J. P. KuENEN, |. ce. p. 142. 
5) W. Ramsay and M. W, Travers, Proc. R.S. 67. 329. .1900. 
