HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
39 
Experiment XI. the further stimulation of the surface by hydrogen is again well 
marked. Moreover, it proved very enduring in character, hardly fading at all during 
several successive experiments with normal electrolytic gas, and, indeed, subsequent 
complete “dehydrogenation” of the surface by oxygen at 400° only reduced the value 
of “k” for normal electrolytic gas to (P6554. It is evident, therefore, that the 
stimulating action of hydrogen was partly due to the surface becoming “ hydro- 
genised,” and partly also to the permanent increase in the surface area when this 
condition was removed. This was very clearly shown in the next two experiments 
(XII. and XIII.). Starting with the gauze in its completed “dehydrogenised” 
condition, hydrogen was again circulated over it at 400° for 16 hours, and afterwards 
rapidly withdrawn from the apparatus. The rate for normal electrolytic gas was at 
once re-determined, as follows :— 
«■ 
Experiment XII. 
Normal electrolytic gas over “ hydrogenised ” gauze. T = 400 . 
t ... . 
0 
i 
4 
1 
3 
¥ 
1 hour. 
p . . . . 
371-1 
203-4 
115-1 
66 -G 
36-6 millims. 
h ... . 
— 
1-0488 
1-0168 
0-9944 
1-006 
The increase in the value of “ hi’ from 0'65 to 1‘04 must he ascribed to the direct 
influence of hydrogen, that is to say, to the association of hydrogen with the surface. 
The combustion tube containing The gauze was now transferred to a high- 
temperature furnace and exhausted, first in the cold, and afterwards at red heat. 
About 9 cub. centims. of hydrogen were extracted during four hours at red heat, and 
the exhaustion was continued for a full hour after the gas had ceased to be evolved. 
The gauze was (tooled in vacuo , and the tube afterwards transferred back to the 
circulation apparatus, where the rate for normal electrolytic gas was finally re-deter¬ 
mined (Experiment XIII.). The complete removal of the hydrogen had left the 
gauze in an extremely “active” condition, owing to the large increase in its surface 
area and porosity. 
Experiment XIII. 
September 26, 1904. 
Normal electrolytic gas. T = 400°. 
t . 
0 
1 
4 
| hour. 
P. 
327-6 
36-6 
2 • 6 millims. 
h . 
— 
3-80 
4-20 
