HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
37 
to the rapid formation and decomposition of an unstable nitride. Graham also 
noticed a very similar effect in his experiments on the occlusion of hydrogen by 
metals. He records that 108*8 grammes of silver wire occluded 0-211 vol. of 
hydrogen (2*2 cub. centims.) when heated to redness and slowly cooled in the gas, 
and that “ the metal acquired a beautiful frosted appearance on the surface, and by 
repeated heating it became highly crystalline and brittle. 
A. 
In its original condition. 
B. After first series of experiments at 400 J 
and subsequent heating (vide p. 36). 
Photomicrographs of the silver gauze. 
In view of the greatly increased surface area of the metal, consequent upon the 
treatment referred to above, we were not surprised to find that its catalysing power 
had increased something like threefold (as compared with the “ normal ” rate in the 
previous series), when the rate for normal electrolytic gas was re-determined (Experi¬ 
ment VII.), as under :— 
Experiment YII. 
September 11, 1904. 
Normal electrolytic gas. T = 400°. Rate of circulation = 1 in 65 minutes. 
t ... . 
0 
1 
2 
1 
l\ hours. 
V ... . 
337-8 
148-2 
45-2 
18 • 6 millims. 
h ... . 
— 
0-7154 
0-8735 
0-8394 
That the enhanced catalysing power of the gauze was really due to its increased 
surface area was proved by rubbing off part of the frosted surface (it was obviously 
* ‘Phil. Trans.,’ 1866, vol. 156, p. 435; also ‘Chemical and Physical Researches,’ pp. 275-277. 
