Corrections of the Nitrogen Scale. 
529 
3. Numerical Data. 
We have now to consider numerical values. In Table I. 
are given the values o£ p c , r c , P , and M. The specific heats 
are assumed to be constant from 0° to 100° except for 
carbonic acid. The value for nitrogen is from Holborn & 
Austin *, the others from Lussana f. For carbonic acid 
Lussana's mean value for a pressure of 1 metre of mercury 
is used as a basis, and the variation with temperature, 
assumed to be linear, is taken from the mean of the results 
of Regnault, E. Wiedemann, and Holborn & Austin. All 
the values refer to a pressure of 1 metre of mercury. 
Table I. 
Critical Constants, Specific Heats, and Molecular Weights. 
Gas. 
Pe. 
(atmospheres). 
T 
(=273+g. 
C^xlO 6 . 
(ergs). 
M. 
(mol. wt.). 
C0 2 
0, 
72-9 
50-8 
393 
33-6 
13 
(19-4) 
304 4 
154-2 
133 
128 
32 
7-90(1+0-001070 
937 
9-91 
9-87 
142-2 
44 
32 
28 8 
28 
2 
Air 
N 
H„ 
The data available on the cooling effect, jju, are those of 
Joule and Kelvin \ on all five ^gases ; of Satanson § and 
of Kester || on carbonic acid ; and of Olszewski IF on the 
inversion-point for hydrogen. Of Joule and Kelvin's 
seventeen experiments on hydrogen, only those have been 
considered in which the impurity of the gas was small 
(Nos. 3, 5, 6, 7, 9, 13, 14, 15, 16, 17), the correction for 
impurity being very large and uncertain. The data for 
plotting the experimental curve y~f(j') are collected in 
* Phys. Rev. xxi. p. 260 (1905). 
+ Nuovo Cimento (3) xxxvi. p. 134 (1894). 
X Kelvin, Math, and Phys. Papers, i. pp. 418-429. 
§ Wied. Ann. xxxi. p. 502 (1888). 
|| Phys. Rev. xxi. p. 260 (1905). 
f Phil. Mag-. [6] iii. p. 535 (1902). 
