150 
DRS. L. MOND, W. RAMSAY, AXD J. SHIELDS OH THE 
(2.) The amount of heat absorbed on the removal of oxygen from platinum black 
can be calculated in a somewhat similar way. 
In Experiment VII., as we have just seen, 38'26 cub. centims. of hydrogen must 
have been left over occluded from the preceding Experiment VI. Be.sides this, how¬ 
ever, 7'95 cub. centims. of hydrogen were pumped off in vacuo in Operation 24, so 
that in ExjDeriment VI., altogether, 38‘26 -j- 7'95 = 4G’21 cub. centims. of hydrogen 
must have been occluded. The total hydrogen absorbed was 90‘a7 cub. centims. ; 
hence 90*57 — 46'21 = 44*36 cub. centims. must have combined with 21*18 cub. 
centims. of oxygen occluded in Experiment V. to form water. 
The evolution of heat corresponding to this formation of water is 
44*36 X 0*00009 X 342 = 1*3652 K. 
Similarly, the heat evolved on the occlusion of 46*21 cub. centims. hydrogen is 
46*21 X 0-00009 X 69 = 0*2869 K. 
The sum of the two heats evolved, viz., 1*6521 K, is greater than the heat actually 
evolved, viz., 1*3268 K, by 0*3253 K. 
Consequently, 0-3253 K must have been absorbed on removing 22*18 cub. ceutims. 
= 0*03172 grm. of oxygen, and hence — 10-3 K were absorbed per gram of oxygen 
removed. 
(3.) Going back another step, we ffnd that, from Exjjeriment VI., 22*18 cub. centims. 
of oxygen must have been occluded in Experiment V. The total oxygen used in 
Experiment V. was, however, 41*80 cub. centims., and therefore 19*62 cub. centims., 
= 0-02805 gram of oxygen, must have formed water with the corresponding quantity 
of hydrogen pre-existing in the platinum black, giving out 
684 X 0-02805 
16 
1*1995 K. 
19*62 cub. centims. of oxygen would remove 39*24 cub. centims. of hydrogen, with 
the absorption of 
39-24 X 0*00009 X 69 = 0*2438 K. 
The heat due to the formation of water and the removal of hydrogen is thus 
1*1995 — 0*2438 = 0*9557 K, whilst the heat actually evolved was 1*3371 K. Con¬ 
sequently, 0*3814 K have been liberated on the occlusion of 0*03172 gram of oxygen ; 
or 12-0 K were evolved for every gram of oxygen occluded. 
All these calculations depend on the final measurement of the oxygen occluded, 
and consequently any error involved in this determination would be magnified at 
each step backwards. 
We have thus obtained three values for the amount of heat evolved per gram oi’ 
