444. W. A. Norton—Force of Hifective Molecular Action. 
that for a certain mixture of oxygen and hydrogen its estimated 
value is about 24; and that for carbon-dioxide it is 3° 
the gas is in the condition and at the temperature referred to 
on page 438, and increases as the temperature falls, to 4'93 at 
about the temperature, —80° C. At the critical temperature 
30°°9 C., its value is 4-7. 
The approximate value of & for any gas at any temperature 
may be readily obtained, for any other temperature for the 
same gas, by the empirical law that it is inversely proportional 
to the ,; power of the absolute temperature. It is to be under- 
stood that the calculations are for the value of & at the maximum 
tension of the gas (vapor) at the temperature considered. 
n the liquefaction of oxygen, hydrogen, and _ nitrogen, 
when the point of liquefaction, so styled, was reached, the dis- 
tance, a, between the molecules, must have been reduced to 
3dr, or very nearly this. This distance answers to the point 
of ebullition of gases whose molecular curve lies just above the 
critical curve (for which k=4-7). By specific heat ratios we 
OT 2-456. The reduction of 
temperature from 15°°5 C. to 145°°5 C. should materially aug- 
ment this deduced value of &. If we assume that the empirical 
law holds for oxygen, as for carbonie acid, that & is in- 
versely proportional to the 7, power of the absolute temper- 
ature, we obtain k=2°64. Now taking u=3°, I find g=1156°2. 
Taking this value of g, and k=2°64, the formula gives P,=272'5 
atmospheres. The volume ratio for the actual gas, for which 
k=2°64, I find to be aS This gives for the density of the 
condensed gas, 0°881 the maximum density of water; on the 
hypothesis that the dimensions of the molecules are unaffected 
by the reduction of temperature. But theoretically this should 
be attended with a contraction of the effective molecules. If 
we assume the law of the consequent diminution in the volume 
of the gas to be the same as that of the increase of & from a fall 
of temperature, the density comes out 0°94. According to 
Professor Pictet’s experimental determinations the elastic gor 
sure of the condensed oxygen was 273 atmospheres; and th 
density 0°98. | 
If we Bippees the original value of & (2-456) to remain un- 
peenee and take w=8°5, the formula gives P,=285 atmos- 
obtain for oxygen, k=4:93x 
_ pheres; and the density is 0°91, or 0-975. For k=2°63, and 
ER P,=273'6 atmospheres; and the density is 0°888, or 
