58 
DR. W. A. BONE AND MR. R. V. WHEELER ON THE COMBINATION OF 
alternating reductions and oxidations of the material composing the surface, it follows 
from the facts brought to light in the above experiments (1) that the rate of reduction 
of the surface by hydrogen at 200° must be excessively small compared with its rate 
of re-oxidation by oxygen, and (2) that the rate of combination with electrolytic gas 
must be comparable with the rate of reduction of the surface by hydrogen. That 
these conditions were not fulfilled will be seen from the following group of 
experiments :— 
2nd Group. 
Normal electrolytic gas was circulated at 200° over the material (which for some 
weeks previously had not been in use) until a constant rate of combination was 
attained. The two following determinations of the rate for normal electrolytic gas 
were then made :— 
Experiment V. 
January 31, 1905. 
Normal electrolytic gas. T = 200°. 
Experiment VI. 
February 1, 1905. 
Normal electrolytic gas. T = 200°. 
t. 
P. 
t. 
P. 
Ai. 
hours. 
millims. 
hours. 
millims. 
0 
367-3 
— 
0 
380-4 
_ 
1 
293-4 
0-0976 
1 
306-2 
0-0943 
2 
215-1 
01162 
2 
235-7 
0-1040 
3 
163-5 
0-1160 
3 
170-4 
0-1163 
4 
126-2 
0-1160 
4 
130-9 
0-1158 
5 
96-4 
0-1162 
5 
100-0 
0-1160 
The fall in pressure during the first hour in each of these experiments corresponded 
with the disappearance of as nearly as possible 20 per cent, of the original gas. 
Pure hydrogen was next circulated over the surface at 200°, but the pressure fell 
from 301'7 to 288'5 millims., or by 4 - 4 per cent, only, during the first hour, a rate of 
reduction whicli is many times slower than the rate of combination with electrolytic 
gas at the same temperature. On raising the temperature of the combustion tube to 
300 , the reduction ol the surface proceeded with fair velocity, the fall in pressure 
being about 100 millims. per hour. The reduction was continued until 2|- litres of 
hydrogen had been used, an amount exceeding the quantity of hydrogen in four full 
charges of electrolytic gas. 
The apparatus was then thoroughly exhausted during 36 hours, and the temperature 
of the combustion tube lowered to 200° again. A charge of oxygen was thereupon 
admitted, and the rate of re-oxidation of the reduced surface determined; the fall in 
pressure observed during the first hour was, however, only 297 out of 406T millims., 
or about 7 per cent., and during the next four hours there was a total further fall of 
