576 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
was 59° Fahr., and the height of the barometer 30- 14 inches ; a uniform exhaustion 
was maintained in the air-pump receiver of 29*3 inches, as observed by the gauge 
barometer attached. 
The constant volume of dry air passed into the vacuum, or was effused, in three 
experiments, in 494, 495, and again in 495 seconds. 
The constant volume of dry hydrogen was effused, in two experiments, in 137 and 
again in 137 seconds. Calculating from 495 seconds as the time for air, we have — 
Time of effusion of air r 
Time of effusion of hydrogen 0*277 
Or, the result may be otherwise expressed, taking the reciprocals of the last numbers : 
Velocity of effusion of air 1 
Velocity of effusion of hydrogen . . . . 3*613 
The specific gravity of hydrogen gas, according to the most recent and exact deter- 
mination, that of Regnault, is 0 06926, referred to air as unity ; of which the square 
root is 0*2632, and the reciprocal of the square root 3*7994 ; to whicti the numbers 
for the time and velocity of hydrogen above certainly approximate. 
Oxygen and Nitrogen. — Temperature 60° ; exhaustion maintained at 29*3 inches. 
The constant volume of air was effused in 494 seconds, of oxygen in 520 seconds, 
and of nitrogen in 486 seconds, in one experiment made upon each gas. Hence the 
following results : 
Time of effusion. 
Square root of 
density. 
Velocity of effusion. 
Reciprocal of square 
root of density. 
Air 
1 
1 
1 
1 
Oxygen 
1-053 
1-0515 
0-9500 
0-9510 
Nitrogen 
0-984 
0-9856 
1-0164 
1-0146 
The densities made use of are those of M. Regnault, namely, 1*10563 for oxygen, 
and 0*97137 for nitrogen. It will be observed, that the times of effusion of these two 
gases correspond as closely with the square roots of their densities as the mode of ob- 
servation will admit of; the times observed being within one second of the theore- 
tical times. 
Carbonic Oxide. — This gas was prepared by the action of oil of vitriol upon pure 
crystallized oxalic acid, and subsequent washing with alkali. The temperature 
during the effusive experiment was 60°*3 ; the usual exhaustion was maintained. The 
time of effusion of air was 494 seconds ; of the same volume of carbonic oxide 488 
seconds : 
Time of effusion, 
air = 1. 
Square root of 
density. 
Velocity of 
effusion. 
Reciprocal of 
square root. 
Carbonic oxide 
0-987 
0-9838 
1-0123 
1-0165 
