8 
DR. W. A. BONE AND MR. R. V. WHEELER ON THE COMBINATION OF 
are of special interest in that they prove how inadequate is any purely chemical view 
of the catalytic process. In the case of ferric and nickel oxides it is possible, within 
certain temperature limits, to obtain a truly catalytic combination at a rate far in 
excess of that at which either the surface itself is reduced by hydrogen alone, or the 
reduced surface reoxidised by oxygen. In the case of copper oxide, it would appear 
that the catalytic process primarily involves the condensation of “ active ” oxygen at 
the surface, and that the film of condensed oxygen actually protects the surface from 
the attacks of hydrogen; indeed, the substitution of inert nitrogen for the oxygen of 
electrolytic gas always produces a very remarkable acceleration of the rate at which 
the hydrogen disappears. 
One of the chief difficulties encountered in experiments of the kind under discussion. 
is the reattainment of the state of “ normal ” activity in a given series of experiments, 
possibly extending over many days or even weeks together, during the course of 
which conditions other than temperature are purposely varied. Indeed, the certainty 
with which the surface can be restored to its “ normal” state after a given change of 
conditions is often a criterion of the value of the series. It is always important, in 
interpreting the results of a particular set of experiments, to take into account the 
past history of the surface, and to follow carefully any changes in its catalytic power 
induced by special circumstances. Throughout the paper, therefore, the experiments 
with a given surface are described in their chronological order, and the date on which 
each experiment was performed is indicated in the tabulated results. 
An Apparatus for Measuring the Velocities of Catalytic Gas Reactions. 
The apparatus employed for measuring the velocity of the catalytic combination of 
hydrogen and oxygen during this research is shown in Diagram I., fig. 1. It is, 
however, well adapted for velocity measurements in the case of other catalytic gas 
reactions when the product can be removed by condensation or absorption by a 
suitable reagent. 
It consists essentially of a closed system in which the reacting gases are circulated, 
at a uniform rate, over the particular surface under investigation, maintained at a 
constant temperature, and afterwards through a cooling or absorption arrangement 
to ensure the rapid removal of the reaction product, in this case steam. The rate of 
combination is, in the case under discussion, measured by observing the pressure in 
the apparatus at regular intervals of time. By means of a series of “bye-pass” 
sampling tubes, samples of the gases can, if necessary, be cut off at intervals during 
an experiment without altering the pressure in the apparatus, or in any way 
interfering with either the course or the conditions of the reaction. 
Two great advantages may be claimed for this apparatus, namely, (1) that with 
ordinary electrolytic gas it allows of velocity measurements being made in a single 
