362 
PROFESSOR GRAHAM ON THE MOTION OF GASES. 
those which follow upon hydrogen, the transpiration times which were obtained foi 
the three portions of the scale already described were 0*7344, 0*7388 and 0*7294, 
which approach the speculative number for carbonic acid quite as closely as the 
experiments previously detailed. 
(4.) The hydrogen was prepared (as was always the case) from zinc which con- 
tained no arsenic, and was passed through a wash bottle containing oxide of lead 
dissolved in caustic soda, and dried by passing over asbestos moistened with oil of 
vitriol. The thermometer was 67° and the barometer 29*506 inches. 
Table VIII. — Transpiration of Air and Hydrogen. 
Pressure by gauge barometer. 
Air. 
Hydrogen. 
Experiment I. 
Experiment II. 
Experiment I. 
Experiment II. 
inches. 
//■ 
// 
20 
0 
0 
0 
0 
15 
221 
221 
107 
107 
10 
328 
328 
158 
159 
8 
188 
185 
92 
91 
6 
251 
251 
121 
121 
4 
422 
423 
176 
178 
2 
579 
580 
310 
308 
From 20 to 2 inches 
1989 
1988 
964 
964 
The results calculated from the means of these experiments are as follows, the 
transpiration time of air being taken as 0*9 : — 
Transpiration times of Hydrogen. 
Air =1. 
Oxygen =1. 
From 20 to 10 inches ... 
From 10 to 6 inches ... 
From 6 to 2 inches ... 
From 20 to 2 inches ... 
0-4845 
0-4866 
0-4859 
0-4867 
0-4352 
0-4371 
0-4364 
0-4371 
The experimental times for hydrogen vary only in the smallest degree at different 
pressures, and almost coincide with the theoretical time for this gas, 0*4375, which 
is one-half of the time of nitrogen and 7-16ths of that of oxygen. This result is so 
important that I shall make no apology for presenting another series of experiments 
in which hydrogen was compared directly with oxygen. 
The temperature during the following experiments was 67°, and the barometer 
29*420 to 29*458 inches. 
