354 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
hydrogen was preserved in a state of great purity by transmitting it by a bent tube 
from the generating retort to the upper part of the pneumatic receiver, and in large 
volumes, so that the gas never passed through water, and was retained only a very 
short time in contact with the surface of that liquid, the transpiration time then fell, 
as will afterwards appear, quite as low as the theoretical number. 
(3.) The transpiration of carbonic oxide took place in 1051 and 1051 seconds, 
against 1090 and 1089 seconds for air; thermometer 58° Fahr., barometer 29'866. This 
gives for carbonic oxide the transpiration times 0‘9646, air = 1 ; and 0‘8690, oxygen = 1 . 
I'he transpiration time of the same gas by the former capillary H wasO‘8674 ; while 
the number corresponding with the theoretical density of the gas is 0'8750. 
The capillary K was now shortened to 39*375 inches, and the following experiments 
were made with it. 
(1.) Carbonic acid was transpired in 661 and 659 seconds, thermometer 58°, and 
barometer 30*024. The time of oxygen was 900 and 903 seconds. The means give 
0*7321 as the transpiration time of carbnnic acid, a number considerably less than 
0*75, and confirming my suspicion that the latter number was too high, and that the 
resistance of H was not sufficiently great to eliminate the whole influence of effusion 
in this gas. It may be remarked, in passing, that the new number for carbonic acid 
approaches 0*7272, which is equal to or is the reciprocal of the density of carbonic 
acid gas. Such a relation suggests the idea that carbonic acid possesses the time of 
oxygen, (of which gas, carbonic acid contains its own volume,) diminished by the 
carbon present, which gives an additional momentum corresponding to its weight to 
the compound gas, and acts thus entirely in increasing its velocity. 
In another series of experiments the numbers were 659 and 659 for carbonic acid, 
against 900 and 902 for oxygen; thermometer 58°, and barometer 30*052. This 
gives 0*7303 as the transpiration time of carbonic acid. 
(2.) Without entering into a detail of the experiments, I may add, that the capillary 
K of its present length gave 0*9034 as the transpiration time of air and 0 4500 as the 
transpiration time of hydrogen ; the time of the latter gas being undoubtedly elevated 
by a minute impurity, as in the former case. 
The length of capillary K was now reduced to 26*25 inches, and in order to in- 
crease the transpiration time, which fell to about 567 seconds for air, the range of the 
attached barometer observed was increased from 3 to 5 inches, the observations being 
made at 28*5 and 23*5 inches of the barometer attached to the air-pump. 
(1.) The times for air were 946 and 945 seconds ; the time for oxygen 1053 seconds, 
giving 0*8979 as the transpiration time of air; thermometer 57° and barometer 
.30*096. 
(2.) The times for carbonic acid were 773 and 773 seconds, the times for air ob- 
served immediately before being 942 and 943 seconds ; thermometer 57° and baro- 
meter 29*982. This gives 0*8202 as the transpiration time for carbonic acid referred 
to air, and 0*7361 referred to oxygen. 
