PROFESSOR GRAHAM ON THE MOTION OF GASES. 
365 
II. TRANSPIRATION OF VARIOUS GASES AND VAPOURS. , ,,,, , 
1. Protocarburetted Hydrogen, CHg. 
It is necessary to mention how this gas was prepared, as it is one, like olefiant gas, 
of which we are never quite certain of the absolute purity. Six hundred grains of 
dried acetate of soda, the same weight of fused hydrate of potash, and nine hundred 
grains of unslaked quick-lime, all in fine powder, were well-mixed in a coated Flo- 
rence flask used as a retort, and the gas brought off by heat. The last portions of 
gas were rejected. The hydrate of baryta never, in my hands, gave so pure a gas, 
when substituted for the hydrate of potash. Free hydrogen, the usual impurity in 
this gas, I have formerly shown to have scarcely any effect upon the rate of carburetted 
hydrogen, when present only to the extent of a few per cent. 
The old experiments with the long 20 feet capillaries E and H, of small resistance, 
agreed remarkably in the transpiration time 0‘5515 for this gas. With capillary M, 
52*5 inches in length, and transpiring into a vacuum, I obtained 684, 686, 685 seconds 
as the time for this gas, against 1 120 and 1120 seconds for air ; thermometer 62°, and 
barometer 29‘844 inches. This gives 0*5504 for carburetted hydrogen for a capillary 
of great resistance. This gas, in a state of compression, was transpired by the same 
capillary into air as in the experiments to follow on olefiant gas. The results, with- 
out details, were as follows : thermometer 64°, barometer 30*050 to 30*074. 
Transpiration of Protocarburetted Hydrogen (into air) by Capillary M, 
52*5 inches in length. 
Air =1. 
Oxygen =1. 
From 20 to 10 inches ... 
From 10 to 6 inches ... 
From 6 to 4 inches ... 
From 4 to 2 inches ... 
From 2 to 1 inch 
0-6304 
0-6254 
0-6269 
0-6335 
0-6349 
0-5495 
0-5490 
0-5515 
0-5525 
0-5607 
From 10 to 1 inch 
0-6321 
0-5541 
The transpiration of this gas appears highly uniform at different pressures. Ex- 
cluding the two observations at the extremes of the scale, the mean result is — 
Transpiration time of protocarburetted hydrogen . . . 0*5510. 
A repetition of the last experiments gave a slightly different series of numbers, 
namely, 0*5583, 0*5497, 0*5541, 0*5523, 0*5549; showing that the slight departure 
from uniformity among the results at different pressures before observed is of an ac- 
cidental nature, and does not follow any fixed law. The mean of the three preferable 
new observations gives 0*5510, or precisely the same result as the former series. 
This number for protocarburetted hydrogen closely approaches 0*5536, which is 
seven elevenths, or of 0*870, the time of nitrogen. The numerical relation may be 
3 B 
MDCCCXLIX. 
