43 
HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
apparatus was again exhausted, and finally the rate for normal electrolytic gas was 
re-determined in Experiment XXV. The results of this experiment prove that the 
“dehydrogenised” foil had become comparatively inactive; as the experiment 
proceeded, however, its catalysing power gradually increased, until finally it attained 
the “normal” value. The striking difference between the course of events in 
Experiments XXIV. and XXV. proves how completely the catalytic process depends 
on the association of the metal with hydrogen. The rate of circulation in these two 
experiments was 1 in 75 minutes. 
Experiment XXIV. 
April 9, 1905. 
T = 400°. Normal electrolytic gas over 
“ hydrogenised ” foil. 
Experiment XXV. 
April 11, 1905. 
T = 400°. Normal electrolytic gas over 
“ dehydrogenised ” foil. 
t. 
P. 
h- 
t. 
P. 
ki. 
hours. 
miHiras. 
hours. 
millims. 
0 
521-0 
— 
0 
479-6 
— 
1 
334-0 
0-7776 
1 
2 
464-7 
0-0272 
1 
257-2 
0-6138 
1 
440-6 
0-0367 
3 
207-0 
0-5344 
2 
376-8 
0-0523 
l 
173-0 
0-4788 
3 
328-8 
0-0546 
u 
120-0 
0•4250 
4 
285-3 
0-0564 
2 
82-6 
0•4000 
5 
240-1 
0-0601 
6 
209-3 
0-0600 
22 
21-1 
0-0616 
At the conclusion of Experiment XXV., the combustion tube containing the foil 
was removed to the absorption apparatus, where it was subjected to the prolonged 
action of hydrogen at dull red heat (650°). After the metal had become fully 
“ hydrogenised,” the tube was cooled and the unabsorbed gas withdrawn. Ihe tube 
was again transferred back to the circulation apparatus, where the rate for normal 
electrolytic gas was re-determined (Experiment XXVI.). The metal was now found 
to be extraordinarily active, so much so that pressure records had to be taken every 
few minutes ; by the end of half an hour no less than 83 per cent, of the original gas 
had disappeared. The values for “/cfi’ are, for purposes of comparison with the 
previous experiments of the series, referred to the hour as the unit of time. 
