HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
23 
Absorption of Hydrogen by Porous Porcelain at Red Heat. 
It was now necessary to ascertain whether or not hydrogen is occluded to any 
appreciable extent by porous porcelain at high temperatures. The combustion tube 
containing material used in the preceding experiments was transferred to the 
“ absorption apparatus” (see Diagram I., fig. 2), where, after a preliminary thorough 
exhaustion at 700°, pure hydrogen, which had been just previously passed over red 
hot copper, was admitted, and the subsequent absorption of the gas by the red hot 
porcelain was followed by pressure readings at frequent time intervals. In three 
different experiments the following records were obtained :— 
t ... . 
0 
1 
2 
3 
4 
5 
10 
15 
20 
30 
60 minutes 
(1) p. . . 
720 
664 
645 
636 
628 
621 
597 
585 
575 
561 
532 millims. 
(2) P . . . 
740 
— 
688 
677 
— 
668 
646 
637 
630 
621 
5) 
(3) P . . . 
766 
706 
693 
686 
680 
674 
665 
657 
650 
633 
>> 
The gas absorbed at red heat was very obstinately retained when the apparatus 
was exhausted at the ordinary temperature. In the third of the above experiments, 
for instance, it was not removed after 10 hours’ continuous pumping. As soon, 
however, as the tube was again heated to redness, the occluded gas could always be 
completely removed after two or three hours’ pumping. 
3rd, Ath and 5th Series.—Experiments with Surfaces C, D and E. 
Whilst the behaviour of these three surfaces resembled that of the surface B in the 
three important respects already referred to on pp. 13 and 14, certain differences were 
observed which must not be overlooked in constructing a theory of the catalytic 
process. 
Surface C. 
The activity of this surface was stimulated by long exposure to hydrogen at the 
ordinary temperature, but not when the treatment was repeated at 450°. The 
stimulating influence of hydrogen at the ordinary temperature is illustrated by the 
results of the following series of experiments, at 430°, with normal electrolytic gas :— 
