and the Properties of Substances. 177 
to unity. An inspection of the table will show that the greatest 
deviation from the square root law in the case of both the 
quantities c, and c, is shown by the hydrogen atom. The 
deviations are in opposite directions. This adds another anomaly 
‘to the large number for which hydrogen is already famous. 
Tasie Il. 
| 
Atomic Atomic 
| symbol V1 y2 symbol Y1 Y2 
| H | -653/1-70 || cl | 920 | 1-171 
i C 1-000 | 1-00 Br (tS | WeikOD 
O ‘974 ‘977 Sn 882 | 1:346 
] F 863 819 if ogi |) Ills 
The writer has deduced two fundamental relations from the 
law of molecular attraction and the laws of thermodynamics’. 
‘These equations may now be written 
(2, 
ee eR a as, Bp (1), 
(2,,) 
> 
! T=M pCa” nh a ARP A a a (2), 
1, )3 
where p denotes the pressure of the substance at the tempera- 
ture 7, and M? and M,? are quantities which have the same values 
for all substances at corresponding states. Thus if the chemical 
formula of a substance be known the critical constants can ap- 
proximately be calculated by means of the atomic constants cy 
and c,. The values of 7, for a few substances were calculated in 
this way by means of equation (2) and are contained in Table III, 
putting for M, its mean value 17°69. The agreement between 
calculation and experiment is not quite so good as obtained in 
Table I, due probably to the fact that higher powers of %, and 
,, are involved which increases the effect of the errors in ‘their 
values on the value of 7,. But still the formulae should be useful 
in obtaining approximately the values of the critical quantities. 
They may be of use in chemical investigations, especially when 
the properties of a new compound are being investigated whose 
chemical formula can only be conjectured. “Thus if the critical 
‘constants of a hypothetical substance be calculated, its pressure, 
* Phil. Mag., Oct. 1909, p. 509, and Dec. 1909, p. 903. 
VOL. XVII. PT. II. 12 
