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DR W. A. BONE AND MR. R Y. WHEELER ON THE COMBINATION OF 
excess of oxygen was only manifested during the initial stages. These facts suggest 
the following view of the catalytic process. Porous porcelain occludes, or condenses, 
both hydrogen and oxygen at rates which depend to some extent upon the physical 
condition and past history of the surface. In general, however, whereas in the case 
of oxygen the process is extremely rapid and the surface layer is soon saturated, the 
occlusion of hydrogen is slower and the limit of saturation much higher. Combination 
between the occluded gases occurs at a rate either comparable with, or somewhat 
faster than, the rate at which the film of occluded oxygen is renewed, but considerably 
faster than the rate of occlusion of hydrogen. 
Part II. —Experiments with a Basic Surface of Calcined 
Magnesite. 
The primary object of these experiments was to ascertain whether a surface 
composed of basic and non-reducible oxides behaves in the same way towards 
electrolytic gas as does the acidic porcelain. The material selected was a specimen of 
magnesite containing considerably less than 1 part of iron in 100,000; it was 
thoroughly calcined at 1000° in a muffle furnace, and then packed into the combustion 
tube of the circulation apparatus. # The packed tube was heated to dull redness in a 
current of dry air for several hours; it was then cooled, and connected with the 
circulation apparatus, where it was thoroughly exhausted at 430° for 24 hours. 
Several successive charges of normal electrolytic gas were then circulated in the 
apparatus, during which the catalysing power of the surface gradually increased up 
to a steady maximum, after which it remained practically constant. This steady 
state was regarded as the “ normal ’ condition of the surface. 
The following series of nine experiments was then made under precisely the same 
conditions as regards temperature (430°) and rate of circulation (namely, 1 in GO 
minutes). In the first experiment, the rate of combination for normal electrolytic 
gas was shown to be directly proportional to the pressure of dry gas. In the second, 
where a mixture of approximately 3H 2 + Oa was employed, it was found to be nearly 
proportional to the partial pressure of hydrogen. 
After Experiment II., hydrogen was circulated over the surface at 430° for 
1G hours, and on redetermining the rate of combination for normal electrolytic gas 
over the “ hydrogenised ” surface in Experiment III., it was found to be abnormally 
high. At the conclusion of Experiment III., the apparatus was exhausted at 430° 
for 1G hours, and on subsequently circulating a fresh charge of electrolytic gas over 
the surface, it was finally restored to its normal condition (Experiment IV.). The 
results of these four experiments are tabulated below :— 
* Tlie calcined material had the following percentage composition:—MgO = 87 - 00, CaO = 12'42, 
ALO, = 0-33, SiOo = 0'25. 
