965 
The density of the liquid at — 183°.15 agrees well with the figures 
given by Baty and Donnan'). The difference is less than 1 °/,. 
Although the deviations of the diameter from rectilinearity are 
sufficiently small to enable one to say that argon obeys the law of 
the diameter, they are still too large, and especially too systematic, 
to be due to experimental errors. As is easily seen from the table 
and from the accompanying figure, the experimental diameter in the 
neighbourhood of the critical point exhibits a curvature concave 
towards the axis of temperature, while at higher temperatures it is 
convex towards the same axis. The same behaviour has already 
been observed in other substances, e. eg. carbon dioxide ®). 
In fig. 8 are given the reduced density curves and diameters for 
ether (Ramsay and Youre ®)), isopentane (Youre *)), oxygen (Marmas and 
KAMERLINGH ONNES*)), xenon (PATTERSON, Cripps and Wurvrraw-Grar °)), 
argon and helium (KAMERLINGH ONNes 5), the reduction from the 
experimental data has been made by means of the critical density 
obtained from the diameter. 
On a previous occasion it was shown by KaMeRLINGH ONNmEs and 
Kerrsom *) how the equations of state for different substances deviate 
one from another, and how, these differences may find expression in 
deviation functions. On doing this, it appears that substances may 
be arranged in order so that the deviations of successive substances 
gradually increase, while it also appears that substances of widely 
divergent critical temperatures are then found to be in the order of 
their critical temperatures. The exemplification of this general pro- 
perty afforded by the behaviour of the diameter was noticed by one 
of us some time ago’) and is brought to light in fig. 3 in which the 
density curves are seen to enclose one another. 
If the law of corresponding states were strictly obeyed, then these 
curves ought to coincide exactly. From the diagram, however, it is 
seen that this is not the case. The curves enclose one another *®) in 
DE CG. Bary and I. G. Donnan, Journ. Chem. Soc. Trans. 81. (1912). p.911. 
2) H. KAMERLINGH ONNES and W. H. Kersom. Proc. Febr. 1908, Comm. 
N°. 104a. J. P. Kuenen and W. G. Rosson, Phil. Mag. (6). 3. 1902. p. 624. 
3) W. Ramsay and S. Youne, Phil. Trans. 178, (1887) p. 57. 
4) S. Youre. Proc. phys soc. London 1894/1895 p. 602. 
5) Le. 
Ee 
7) H. KAMERLINGH Onnes. Proc. Dec. 1911, Comm. NP, 1245. 
8) Enc. Math. Wiss. V. 10. Suppl. N°. 23. 
9) E. Marutas C. R. 139, (1904), p. 359. 
10) In the diagram of N?. 36 of Enc. Math. Wiss. V. 10. Suppl. NY. 23, is 
clearly shown the surrounding of the boundary curve for helium by that for iso- 
pentane. 
