OCCLUSIOISr OF OXYGEN AND HYDROGEN BY PLATINUM BLACK, 
135 
quite parallel with the first part owing to the very slow absorption going on. Instead 
of drawing the tangent to part III. of the curve, which would obviously be wrong, 
a closer approximation to the true deflection can be obtained by drawing a parallel to 
part I. of the curve through the last point of observation, at which point the volume 
of occluded hydrogen was determined. 
Blank experiments showed that admission of the relatively small quantity or gas 
from the burette to an empty experimental tube produced no appreciable deflection. 
Several preliminary experiments were made, using small quantities ot platinum 
black, but the results of these were unsatisfactory on account of the difficulty of 
measuring the deflection and the amount of hydrogen occluded accurately enough. 
To obviate this difficulty, experiments were made on a larger scale, and with as much 
platinum black as could conveniently be introduced into the experimental tube. The 
results of these experiments are given in the following Table I., the experimental 
tube beino’ removed from the calorimeter, re-exhausted at 184 C., and replaced in 
the calorimeter again before admitting hydrogen the second time. 
Table I. 
Experi¬ 
ment. 
1 
Platinum 
black used. 
Hydrogen occluded. 
Heat evolved. 
1 
Heat evolved per 
gram of hydro- ; 
gen occluded. 
1 
1 
---- 1 
Deflection. 
Heat in calories. 
1 K = 100 cal. 
h. 
i 
grams. 
9-744 
9-744 
cub. centims. grams. 
8-34 0-000751 
7-38 0-000664 
millims. 
49-6 
43-6 
K. 
0-05223 
0-04591 
K. i 
69-6 
69-1 
Table II. 
Experi¬ 
ment. 
Platinum 
black used. 
Hydrogen 
occluded. 
Heat 
Deflection. 
evolved. 
Heat in caloiues. 
1 K = 100 cal. 
Heat evolved per 
gram of hydro¬ 
gen occluded. 
grams. 
cub. centims. 
grams. 
millims. 
K. 
K. 
i let. 
9-744 
-2-51 
-0-000226 
-14-1 
— 0-01485 
-65-7*- 
! 15. 
9-744 
2-13 
0-000192 
11-6 
0-01221 
63-7 
III. 
1-9193 
1-90 
0-000171 
11-1 
0-01169 
68-3 
The mean of the two results is an evolution of 69‘4 K per gram of hydrogen 
occluded. This value, however, may represent the sum of two other values, one of 
which relates to the heat evolved on the occlusion of the hydrogen, which can be 
* Heat absorbed pei’ gram of hydrogen removed. 
