HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
17 
Now since the rate of diffusion of hydrogen is four times that of oxygen, it follows, 
assuming the rate of combination at the surface to be infinite, that with normal 
electrolytic gas there will always be an excess of hydrogen at the surface. The rate 
of steam formation would, therefore, be determined by the rate of diffusion of the 
oxygen. This conclusion is obviously not incompatible with the results of the 
previous experiments with the normal gas. Applying the same argument to cases in 
which the gases are not present in their combining proportions, it follows that so long 
as the hydrogen exceeds one-third of the total volume its rate of diffusion will 
maintain it in excess at the surface, and the rate of steam formation should depend 
on the partial pressure of the oxygen only. As soon, however, as the hydrogen falls 
below this limit, the rate should depend on the partial pressure of the hydrogen only. 
In tabulating the results of these experiments it will be necessary to record in 
separate columns the partial pressures of both hydrogen and oxygen, as well as the 
constants calculated from each set of partial pressures. In this way the influence of 
each gas on the rate of change can be seen at a glance. In the following tables, 
therefore :—- 
t = time in hours from the beginning. 
P = 
P H., = 
p o = 
*H«" 
total pressure of the dry gas (corr.) in the apparatus, 
the partial pressure of the hydrogen. 
the partial pressure of the oxygen, 
p 
1 , r °H 2 
7 lo gp-• 
1 ^h 3 
- lo g tT^- 
t P, 
o 2 
T = temperature of the combustion tube. 
Experiment Y. 
March 21, 1904. 
Original mixture = 3H 2 + 0 2 nearly. The rate of circulation was rapid, and [32 • 5 per cent, of the 
original oxygen disappeared during the first two hours. — February 10, 1906.] T = 430°. 
t. 
P. 
p h 2 . 
p o. 
/j h 2 . 
k o 2 . 
hours. 
millims. 
millims. 
millims. 
0 
411-8 
311-8 
100-0 
— 
— 
2 
314-2 
246-7 
67-5 
0-0509 
0-0853 
4 
243-4 
199-5 
43-9 
0-0485 
0-0894 
6 
184-9 
160-5 
24-4 
0-0481 
0-1021 
8 
144-2 
133-4 
10-8 
0-0461 
0-1208 
10 
117-4 
115-5 
1-9 
0-0431 
0-1721 
VOL. CCYI.—A. 
D 
