HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
53 
Part YI.—Experiments with Nickel. 
The nickel was employed in the form of a rectangular piece of gauze, containing 
10 strands per centimetre, and measuring 15 by 14 centims. The surface exposed to 
the reacting gases was approximately 330 sq. centims. The metal proved to be a 
very efficient catalyser, although its catalysing power was rather sensitive to 
comparatively small changes in temperature. Thus in three preliminary experiments 
(Nos. I. to III. inclusive) at 200°, 220°, and 240°, the rate of circulation being 1 in 
40 minutes, the mean values of “ Jo” obtained were 0‘010, 0 - 045, and 0'350 
respectively. 
The ratio IL/Cb for the residual gas from Experiment II. was found to be exactly 
2‘0, and in the case of Experiment III. it was 2 - 2. Apparently, therefore, the 
prolonged action of the gases at 240° caused a slight oxidation of the metal, which, 
however, did not occur at 220°, the temperature chosen for all the succeeding 
experiments. 
At 220°. 
On circulating successive charges of normal electrolytic gas over the gauze at 220°, 
its catalysing power increased up to a point such that from 12 to 15 per cent, of the 
gas always disappeared during the first hour of a given experiment. After this point 
had been reached, however, the values of “ ” increased regularly during each 
experiment, as though the activity of the surface was being continually stimulated as 
the combination proceeded. This induced activity almost entirely disappeared during 
the interval between two successive experiments, when the apparatus was continuously 
exhausted. This is shown by the two following experiments with normal electrolytic 
gas. The rate of circulation for these, as well as all the other experiments of the 
series, was 1 in from 35 to 40 minutes. 
Experiment IV. 
May 29, 1905. 
Normal electrolytic gas. 
Experiment Y. 
May 31, 1905. 
Normal electrolytic gas. 
t . 
P. 
h - 
t . 
P. 
h - 
hours. 
millims. 
hours. 
millims. 
0 
514-7 
— 
0 
505-6 
— 
1 
452 • 1 
0-0564 
1 
437-6 
0-0625 
2 
376-3 
0-0680 
2 
352-9 
0-0781 
3 
301-6 
0-0774 
3 
260-1 
0-0962 
4 
242-9 
0-0817 
4 
199-1 
0-1012 
5 
178-4 
0-0922 
7 
87-6 
0-1099 
The continuous stimulation of the surface in each of the above experiments was not 
due to any permanent oxidation of the gauze, since the ratio H 2 /0 2 for the residual 
