146 
DRS. L. MOND, W. RAIMSAT, AND J. SHIELDS OH THE 
Table III.—Calorimetric Experiments on the Occlusion of Oxygen by 
Platinum Black (continued.) 
Experi¬ 
ment. 
Opera¬ 
tion. 
Gas. 
Gas absorbed. 
Calorimeter 
deflection. 
Heat 
evolved. 
K= 100 
gram. cal. 
Heat 
evolved 
per gram 
of gas 
absorbed. 
Admitted. 
Exhausted. 
VI. 
24. 
cub. centims. 
115-05 Hj 
cub. centims. 
[24-48] 
32-43 
cub. centims. 
90-57 Ho 
grams. 
0*00815 Ho 
millims. 
1260-0 
1-3268 
K. 
162-8 
: vir. 
25. 
20. 
-- 
4-79 0,. 
60-76 „ 
Hil 
[24-75] 
4-79 Oo 
36-01 „ 
0-00685 Oo 
0-05149 
199-5 
1012-8 
0-21C0 
1-0663 
30-6 
20-7 
Totals . 
40-80 „ 
• • 
• • 
1-2763 
1 
' 
i vm. 
1 
27. 
Oxygen occluded. 
Exliansted at a red heat 
i 
21-67 Oo 
0-03098 Oj 
. 
Let us consider first of all the first experiment of five operations. Staiting ^^ith 
the platinum black prepared as above, successive quantities of oxygen were added 
until after Operation 5 it was fully charged up with oxygen. The absorption of the 
oxygen in the first three operations was very rapid, but became slowei in the fouith 
and still slower in the fifth. The table sufficiently explains itself. In Operations 
1, 2 and 3, the heat evolved per gram of oxygen absorbed remains pretty nearly the 
same. In Operation 4 there is a distinct diminution in the amount of heat evolved, 
whilst in 5 this has tailed off to 10 K. These results are remarkable. If all the 
numbers in the last column had remained constant, we might have concluded that we 
were dealing only with the direct occlusion of oxygen, or, even if the last two or three 
values had remained constant we might have accepted these as representing the heat 
of occlusion of oxygen. As it is, however, and knowing as we do that the platinum 
black, in spite of the treatment to which it was subjected, may have contained some 
platinum hydrogen, we must conclude that the first four numbers, at any rate, aie 
composite numbers partially due to the heat of occlusion of oxygen and pai dally to 
the heat of formation of water. It might have been expected that the fiist chaige of 
oxygen would have removed all the hydrogen existing in the platinum, and it is 
curious that for small concentrations of platinum hydrogen, the ratio of the quantity 
of oxygen which goes to form water to that which is occluded remains constant, foi 
this is obviously what the approximate constancy of the first three numbers means. 
For greater concentrations of platinum hydrogen, as can lie seen from Opeiation 16, 
this no longer holds good. 
