( 1020 ) ' 
substances, as is evident from the table of values given by KUENEN *) 
Hence, D. BeRTHELOT Ss *) estimate is probably much too low. 
c. Let us write the equation of the rectilinear diameter of CAILLETET 
and Maruias*) in the form 
lig + Ovap 
in which vig, Cvap and or are the liquid, vapour and critical densities 
respectively and « is the slope of the diameter; calling 
Tr. 
Chee CL 
Ok 
the reduced slope, we can, with the liquid densities published by 
BaLy and Donnan‘), and the value of the critical density already 
published, deduce from the isotherms 
a = —- 0.003050 
ON 0.9027. 
The inelination of the diameter for argon is, therefore, unusually 
great — greater than has ever yet been found for any other substance, 
since « for most substances lies between — 0.0005 and —0.0025 ®). 
In connection with the foregoing, it is of interest to note that 
Youre ®) discovered an intimate relationship for substances of higher 
critical temperature between the diameter’s inclination and curvature 
and the values of the critical volume deduced from the law of the 
diameter. Representing the curved diameter by 
a aa Pal + cat 
ee ( ON i 
= \ Lig | Yvap 
then we obtain the following corresponding relations 
— by << 098) Aa 3.77 va 0 
-—— ba ME == Si kg == 
ENNE > 3.17 cad: 
On a former occasion’) the diameter was considered to be straight 
in which 
) J. P. Kuenen, Die Zustandsgleichung, p. 60. 
) D. BertHetot, Journ. de phys. (3). 10. 611. 1901. 
) L.-CGAILLETET and E. Marutas, Journ. d. phys. (2). 5. 549. 1886, 
4) k. G. C. Baty and F. G. Donwan, Journ. chem. Soc. 81. 911. 1902. 
) E. Matratas, Le point critique des corps purs, p. 9 and 10. 
S. Youre, Phil. Mag. (5). 50. 291. 1900 
