Proceedings of Royal Soeiety of Edinhurgli. [sess. 
84 
of the liquid, at absolute temperature t, we know that the latent 
heat is expressed by the formula — 
From Amagat’s data I find for the values of this quantity, and 
for the ratio of the densities of the liquid and vapour ; — 
Temperature C. X 
0° 4*369 9*023 
10 3*788 6*200 
20 2*882 3*823 
30 1*460 1*906 
Taking the density of CO 2 at 0° C. and 1 atm. as 0*002, it 
is easy to see that the values of X must be multiplied by 
500 2U7 
62”5 ' 1T90 ’ 
= 12*2 nearly, 
to reduce them to ordinar}^ heat units. Thus the latent heat at 
0° C. is about 53, while at 30° C. it is only 17*8. 
In the following table P represents the gain of energy from the 
liquid state to that of saturated vapour, at the indicated tempera- 
ture : — i.e., 
while 
is the corresponding gain of energy, in the critical isothermal, 
between the same limits of volume. 
Temperature C. P 
0° 
3*747 
10 
3*244 
20 
2*459 
30 
1*233 
Q 
3*577 
3*113 
2*409 
1*203 
