144 
DRS. L. MOND, W. RAMSAY, AND .T. SHIELDS ON THE 
the oxygen in platinum black be discharged by the addition of even considerably less 
than the theoretical quantity of hydrogen, the resulting substance still contains 
platinum oxygen and platinum hydrogen existing together, and that the quantity of 
hydrogen pumped off such a mixture at a red heat, in vacuo, even although relatively 
small, does not necessarily represent the actual amount of hydrogen existing in the 
mixture as platinum hydrogen, but only that fraction of it which escapes the catahMic 
action of the platinum or platinum oxygen. 
In the experiments which follow an attempt was made to reduce the amount ot 
this hydrogen to as small an extent as possible. The apparatus used was precise!}’ 
similar to that employed for the determination of the heat evolved on the occlusion 
of hydrogen. The amount of platinum black used was 12-555 grams, and after its 
introduction, the capacity of the experimental tube was carefully determined. 
According to calculation the above quantity of platinum black contained 55-18 cub. 
centims. of oxygen, and this requires for its complete conversion into water about 
110 cub. centims. of hydrogen. Before placing the appai’atus in the calorimeter it 
was sealed on, on one side to the pump, and on the other to the burette supplying 
pure hydrogen. After completely exhausting, at the ordinary temperature, 9G-40 
cub. centims. of hydrogen were admitted and allowed to remain overnight Next 
day communication was made v ith the pump, and whilst the platinum black was 
heated in boiling aniline (temp. 184° C.), as much water and gas as possible were 
pumped off. In this way 1-52 cub. centims. of hydrogen were extracted. The 
experimental tube, in the vacuous state, was then removed from the pump and 
burette and its contents thoroughly mixed up by prolonged shaking. After having- 
been shaken at intervals for a day it was cooled to 0° C. and inserted into the calori¬ 
meter and sealed on once more to the pump and to the Imrette, furnishing pure 
oxygen. 
It was hoped that by this treatment all the platinum hydrogen might be destroyed 
and that the specimen would be able to occlude oxygen directly. Oxygen was, therefore, 
admitted in small poi’tions of about 5 cub. centims. at a time, and the results are 
o’lven in talmlar form in Table III. For the sake of convenience, all the results have 
been tabulated together, and have been further sub-divided into a series of eight 
experiments, or twenty-seven operations. 
