56 
DR. W. A. BONE AND MR. R. V. WHEELER ON THE COMBINATION OF 
partial pressure of the hydrogen (in the case of silver, however, this only holds good 
up to a point of “ maximum hydrogenation ” of the surface). 
The evidence in favour of the “ occlusion” theory is particularly strong in the case 
of nickel, where the “ normal ” condition of activity can be reduced to almost 
vanishing point by prolonged exhaustion at a comparatively low temperature. 
Moreover, the subsequent recovery of activity can be demonstrated by circulating 
successive charges of electrolytic gas over the surface under conditions which entirely 
preclude any chemical action of either of the reacting gases on the metal. 
Part VII. —Experiments with Easily Reducible Metallic Oxides. 
It remained now to examine the action of easily reducible oxides, and for this 
purpose calcined spathic iron ore, copper oxide, and nickel oxide were selected. A 
necessary condition for the complete success of the experiments was the finding, in 
each case, of some temperature at which the catalytic combination of the gases would 
proceed with fair velocity without the surface itself undergoing any permanent 
change. This condition was fulfilled at 200° in the cases of calcined spathic iron ore 
and copper oxide, and at 160° in the case of nickel oxide. 
A. Experiment with Calcined Spathic Iron Ore. 
The catalysing material was prepared by calcining fragments of spathic iron ore at 
didl red heat in a current of air. It contained 79’0 per cent, of ferric oxide and 
14'5 per cent, of manganous oxide. 
1st Group. 
The very powerful catalysing action of these oxides at 200° may be judged from 
the following experiment with normal electrolytic gas. Readings were made every 
10 minutes during the first hour, but, for purposes of comparison with later 
experiments, the values of “ are calculated oil the basis of an hour as the unit of 
time. 
Experiment I. 
November 28, 1904. 
Normal electrolytic gas. T = 200 J . Rate of circulation = 1 in 60 minutes. 
t. 
P. 
h. 
t. 
P. 
h. 
minutes. 
millims. 
minutes. 
millims. 
0 
373-5 
— 
50 
219-0 
0-2783 
10 
336-5 
0-2724 
60 
197-5 
0-2767 
20 
302-5 
0-2748 
80 
163-5 
0-2691 
30 
272-5 
0-2738 
140 
86-7 
0-2718 
40 
243-5 
0-2787 
