OCCLUSION OF OXYGEN AND HYDROGEN BY PLATINUM BLACK. 
151 
oxygen occluded, or, what in one case amounts to the same thing, viz., the heat 
absorbed per gram of oxygen removed. 
From Experiment VII. 
11T K per gram occluded 
VI. . . 
— 10'3K ,, removed 
V 
n 5j .. 
12 0 K „ occluded 
The mean of the three is IIT K per gram of oxygen occluded, and the first of 
these, for reasons which have just been stated, is the most trustworthy. Deviations 
due to the magnification of any errors, are already apparent in the next two, although 
it is satisfactory to find that their mean is identical with the first. If it had been 
] 30 ssible to obtain another pair of values, then from the method of calculation the 
fourth would probably have been less than 10’3, and the fifth greater than 12'0, 
although the mean might have approximated to LIT K. 
Altoerether, therefore, we have six determinations of the heat of occlusion of 
oxygen, three of which were obtained more or less directly, whilst the other three 
were Indirect measurements, namely :— 
From Operation 
K. 
From Experiment 
K. 
5 
10-0 
VII. 
Ill 
10 
14-4 
VI. 
10-3 
23 
11-8 
V. 
12-0 
Of these, 14‘4 K is obviously too high, since the final amount of oxygen absorbed 
in Operation 10 is so large that it probably includes some heat due to the formation 
of water. 
The mean of the other five determinations is -f ll’O K per gram of oxygen 
occluded, and we think, although from the nature of the experiments and the diffi¬ 
culties encountered in determining this constant it is scarcely so satisfactorily 
established as the corresponding number for hydrogen, this value may be accepted 
as a pretty fair approximation to the amount of heat evolved per gram of oxygen 
occluded, or referred to a gram-atom of oxygen + 17G K. 
VI. S 2 yeculations on the Nature of the Occlusion of Gases by Platinum Black. 
With regard to the occlusion of hydrogen and other gases by platinum black, we 
are not as yet in a position to form a definite opinion. The difficulties which lie in 
the way are considerable, and when we remember that the cjuestion, whether the 
much better defined product obtained by occluding hydrogen in palladium is to be 
regarded as containing the compound Pdgll., or whether it is simply a solid solution 
of hydrogen in palladium, has not yet been definitely settled, it is not astonishing 
