r 129 ] 
YI. On the Occlusion of Oxygen and Hydrogen hy Platinum Black, —Part II. 
By Ludwig Ph.D., F.P.S., William PtAMSAY, Pli.D,, F.R.S., and John 
Shields, D.Sc., Ph.D. 
Keceivccl July 21, 1897. 
Contents. 
Page. 
I. Introduction.129 
II. The Heat of Occlusion of Hydrogen by Platinum Black.130 
III. On some Attempts to remore the Oxygen from Platinum Black without destroying 
its Occlusive Power. (Occlusion of SO 2 , CO, NH,, Ac.).138 
IV. On the Existence of Platinum Oxygen and Platinum Hydrogen in Presence of 
each other.141 
V. The Heat of Occlusion of Oxygen by Platinum Black. 143 
VI. Speculations on the Nature of the Occlusion of Gases by Platinmn Black .... 1.51 
I. Introduction. 
In a former paper (‘ Phil. Trans.,’ A, 18 95, vol. 186, p. 657-693) we gave an account 
of some experiments on the occlusion of oxygen and hydrogen by platinum black, and 
pointed out that freshly-made platinum black invariably contains a considerable 
quantity of oxygen. Most of the specimens which we examined contained approxi¬ 
mately 100 volumes, or 0'66 per cent, of oxygen, which could only be completely 
removed hy heating in vacuo at a dull red heat, and although a large fraction of the 
total oxygen can be extracted at about 400° C., the substance which remains behind 
is no longer platinum black but platinum sponge which has a much lower absorptive 
power for gases. 
When hydrogen is admitted to platinum black containing x volumes of oxygen, 
2x volumes are converted into water, and the remainder of the gas absorbed, which, 
in general, is about 100 volumes, is really occluded. The heat evolved on the 
occlusion of hydrogen by platinum black has been measured by Berthelot (‘ Ann. de 
Chim. et de Phys.,’ 1883, vol. 30, p. 519), and by Favre (‘(lomptes Ptencl.,’ vol. 77, 
p. 649, and vol. 78, p. 1257), but we have already (loc. cit., p. 693) expressed our¬ 
selves as dissatisfied with the results they obtained, since the heat due to the 
combination of the oxygen pre-existing in the platinum black with the hydrogen is 
also included in these measurements. 
VOL. CXC.—A. 
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