HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
35 
attained a steady maximum. From this point onwards the rate remained nearly 
proportional to the partial pressure of the hydrogen. The significance of these 
results will be considered later. 
At the conclusion of Experiment II., successive determinations were made of the 
rate for normal electrolytic gas (1) after the surface had been subjected to the action 
of oxygen at 450° for 36 hours, and (2) after the apparatus had been further 
exhausted during 12 hours. The results of these two experiments, which are 
tabulated below, show that oxygen per se has no stimulating influence on the activity 
of the surface, but rather, owing to its !£ dehydrogenising ” action, the reverse. The 
long exhaustion which intervened between the two experiments completely restored 
the surface to its normal condition. 
Experiment III. 
July 27, 1904. 
Normal electrolytic gas after treatment with oxygen 
36 hours. T = 400°. Rate of circulation = 1 in 
60 minutes. 
Experiment IV. 
July 28, 1904. 
Normal electrolytic gas. Surface in “normal” 
condition. T = 400°. Rate of circulation = 1 in 
60 minutes. 
t. 
P. 
h. 
t. 
P. 
h- 
hours. 
millims. 
hours. 
millims. 
0 
470-4 
— 
0 
467-3 
— 
1 
357-4 
0-1193 
1 
336-2 
0-1430 
2 
256 • 6 
0-1316 
2 
240-7 
0-1441 
3 
167-8 
0-1492 
3 
170-3 
0-1462 
4 
112-6 
0-1552 
4 
120-6 
0-1471 
5 
71-2 
0-1640 
The results of the last two experiments of the series (V. and YI.) are chiefly 
interesting in that they point to a theory of the catalytic process. Starting with the 
surface in the “normal” condition, a mixture containing an excess of hydrogen was 
admitted to the apparatus, and the rate of combination observed until nearly the 
whole of the oxygen had disappeared (Experiment V.). During the interval between 
Experiments Y. and YI., hydrogen was circulated over the gauze at 400° for 18 hours 
and then pumped out of the apparatus. Immediately afterwards the rate for normal 
electrolytic gas over the “ hydrogenised ” surface was determined (Experiment YI.). 
The results of the two experiments are tabulated below :— 
