HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 
41 
to the burning out of the small amount of residual occluded oxygen. The pressure 
records during the absorption of hydrogen were as follows :— 
The tube was finally exhausted (I) at the room temperature for an hour for the 
removal of any unabsorbed gas, and (2) at dull red heat for 40 hours, during which 
no less than 26 cub. centims. of hydrogen were very slowly extracted. 
[ Third Series with Silver Gauze at 500°. 
In a series of experiments with normal electrolytic gas at this temperature, it was 
proved that the rate of combination, although very fast, still remained proportional 
to the partial pressure, and that, as at 400°, the catalysing power of the surface was 
stimulated, in a marked degree, by previous exposure to hydrogen.— January 31, 
1906.] 
Fourth Series with Silver Foil at 400 . 
In order to ascertain whether the catalytic process is materially influenced by the 
physical character of the surface, a final series of experiments was made at 400° with 
pure silver foil. A piece of pure “ assay ” silver was rolled out into a thin ribbon 
(40 centims. long and 1*5 centims. broad), and after its surface had been slightly 
etched by momentary immersion in cold dilute nitric acid, followed by a thorough 
washing with hot distilled water, it was wound spirally round a glass rod. The 
extremities of the rod were provided with small glass projections, so that it would 
rest inside the combustion tube of the circulation apparatus without the foil 
touching the glass walls. The area of the foil exposed to the reacting gases was 
60 sq. centims. 
Successive charges of normal electrolytic gas were circulated over the foil at 400 c , 
until the rate of combination, which was at first rather slow, had attained a steady 
maximum. The values of “ Jci” increased from 0'0310 to 0‘0770 during this period, 
after which the rate of combination remained proportional to the pressure of the dry 
gas. This is shown in Experiment XXII., which gives the normal value of “ for 
the series. 
VOL. CCVI.-A. 
G 
