142 
DRS. L. ?>iOXD, 4V. RAMSAY, AA^D J. SHIELDS OA THE 
CO., 
0., ' 
h; 
Residue .... 
2'53 cub. centime. = 10'5 vols. 
3-04 „ „ = 12-7 „ 
o-OO „ „ = 20-8 „ , 
0T8 „ „ = 0'7 „ j 
1 
Total. 
1075 ,, „ = 44’7 „ 
It would appear, therefore, from this experimeut that the hvdrog’en, on being 
admitted to the platinum black, attacks the portion with which it first comes in 
contact, converting the oxygen into water, and then takes its place, instead of first 
converting as much as possible of the oxygen into water. It is also noteworthv that 
the oxygen and hydrogen pumped off did not combine on passing over the heated 
platinum black or sponge, but this, perhaps, may be due to the fact that they come 
ofi‘ at difterent temperatures, and that the bulk of the gas diffused at once into the 
Topler ])ump, which had a much larger volume than the experimental tube. If this 
explanation is correct, then, even on allowfing the tube to stand for weeks or months 
one could scarcely expect all the admitted hydrogen to combine with the oxj’gen in 
the platinum black, since the hydi'ogen is practically not given off into the vacuum 
again, and consequently could not diffuse along to the other end of the tube contain¬ 
ing the occluded oxygen, and vice versd. 
That the explanation wm have given is substantially correct was proved bj^ slightly 
modifying the conditions of experiment. 
5'330 grams of platinum black was divided into two portions of 2’608 grams and 
2722 grams, which were introduced into the hard-glass tubes, A and B respectivelv, 
of fig. 4. 
Fig. 4. 
^ B 
Pump ■*- - 6 I t r ~ ^ i 1 I 1 -Ltl—± 
C B £ 
The two portions were thus separated by a narrow tube provided with a stop-cock, 
D. When the wdiole apparatus, C A D B E, was exhausted, the stop-cock, G, was 
shut. It was calculated that 46'86 cub. centims. of hydrogen were sufficient to 
convert all the oxygen in both portions of the platinum black into water. 48‘00 cub. 
centims., or rather more than what was theoretically necessary, were admitted from 
a gas burette through the stop-cock, E. After standing for about two hours, the 
communication between the two tubes remaining open all the while, the tap, 0, was 
opened, and it was found that the vacuum inside the apparatus was practically 
complete, or that all the hydrogen which had been admitted was absorbed. 
The stop-cock, D, was now closed, and the tube. A, nearest the pump, heated to a 
dull red heat and exhausted. When the exhaustion was complete, D was opened, and. 
