44 
DR. W. A. BONE AND MR. R. V. WHEELER ON THE COMBINATION OF 
Normal electrolytic gas 
T = 400° 
Experiment XXVI. 
April 15, 1905. 
over surface previously treated wit.li hydrogen at 650°. 
Rate of circulation = 1 in 75 minutes. 
t. 
P. 
h- 
1 
t. P. 
h. 
minutes. 
millims. 
minutes. 
millinxs. 
0 
497-2 
— 
15 
185-2 
1-716 
5 
355 • 2 
1-754 
20 
138-2 
1-668 
10 
254 • 2 
1-749 
30 
80-2 
1 -585 
The remarkable influence of hydrogen on the activity of the metal is strikingly 
illustrated by the four pressure curves, for normal electrolytic gas, reproduced in 
Diagram IV., p. 45. Curve A was obtained with the surface in its “normal ’ 
condition, and C after complete “ dehydrogenation ” with oxygen. Curves B and D 
show the influence of “ hydrogenation” at 400° and 650° respectively. 
During the course of the experiments just described, a bright mirror of silver had 
formed along the whole length of the glass rod round which the ribbon had been 
wound, and the inner surface of the combustion tube had become completely coated 
with a thin brown film, suggestive of the decomposition of a volatile compound 
of silver. 
Summarising now the results of the four series of experiments, it is evident (1) that 
with normal electrolytic gas the rate of combination is proportional to the pressure of 
the dry gas; (2) that the activity of the surface is always greatly stimulated by 
previous treatment with hydrogen, but not with oxygen; (3) that an “active ’ 
surface absorbs hydrogen both at 400° and at dull red heat; and (4) that the 
behaviour of the “ hydrogenised ” metal suggests the formation of a hydride rather 
than the mere occlusion or condensation of the gas. The theory of the catalytic 
action of the metal indicated by the facts is that it essentially involves the rapid 
formation and oxidation of a hydride, or at least of a film of “ hydrogenised ” silver. 
Two independent velocities, namely, that of “ hydrogenation ” (Yj) and that of the 
oxidation of the “ hydrogenised ” metal (V 2 ), therefore come into play during the 
process, and the relative values of the two will, in any particular case, depend on the 
condition of the surface as regards its power of combining with hydrogen. In the 
experiments with the gauze, for example, it is evident that V : was faster than Y 2 , for 
with mixtures containing excess of hydrogen the catalysing power of the surface was 
quickly stimulated up to a certain limit of complete “ hydrogenation,” after which the 
velocity of steam formation was nearly proportional to the partial pressure of the 
oxygen (vide Experiments Y. and X.). In the case of the foil, however, it is evident 
from the results of Experiment XXIII. that V ? was slower than Y 2 , for the velocity 
