148 
DRS. L. MONO, W. RAMSAY, AND J. SHIELDS OH THE 
the hyclrogeii was admitted at full atmospheric pressure. The volume of hydrogen 
required to fill the experimental tube is given in square brackets [24’74], whilst 
30’89 cub. centims. were afterwards extracted, the difference between them having 
been removed from the platinum in vacuo. 
Operation 15 is interesting, as the value 68-2 K represents the true heat of occlu¬ 
sion of one gram of hydrogen, which is in good agi'eement with the values formerly 
obtained, the mean of which was about 69 K. 
Just as in the case of 6 , Operations 11 , 12 , and 13 can be calculated in a similar 
way, and give the following values per gram of oxygen removed, if wm assume that 
in each case the whole of the hydrogen is oxidised to water, and that none goes to 
form ]ilatinum hydrogen. 
Operation 11 .... — 18-4 K per gram of oxygen removed. 
„ 12 .... — 20T K 
„ 13 ... . — 21-3K 
Experiment V. is similar to I. and III., except that wn start iii this case with 
platinum black, which has been fully charged with hydrogen, and from wdiich all the 
hydrogen which comes off in vacuo at 0° C. has been removed. 
For the first addition of oxygen a greater amount of heat is evolved, viz., 30‘6 K, 
probably due to the relatively large formation of wmter compared wdth the quantity 
of oxygen really occluded. The last charge of oxygen gives out IFS K per gram of 
oxygen absorbed, and this seems to be due for the most part to fhe true occlusion of 
oxygen. 
At this stage we intended to stojj the series of experiments and to find out, by 
exhausting at a red heat, how much oxygen had actually been occluded in the last 
set of operations ; but, since there was some uncertainty wdiether the wmter wdiich 
was formed was itself occluded or absorbed by the platinum, producing heat changes, 
or whether it simply condensed on the inner walls of the experimental tube and on 
the platinum black, it seemed that some light might be thrown on this point by a 
slight alteration in subsequent experiments. 
The high value, 30-6 K, was obtained in Operation 16 : but before this experiment 
was performed, the platinum black previously charged with hydrogen was kept in 
communication wdth a P 3 O 2 tube in vacuo for two days, in order to remove as 
much as possible of the wmter along with the hydrogen. In Operation 24 
the platinum black was fully charged witli hydrogen. [24-48] cub. centims. were 
required to fill the experimental tube, whilst 32-43 cub. centims. w-ere pumped off as 
expeditiously as possible, in order to leave most of the wmter formed, wdiich diffuses 
very slowly through the capillary tubing, in the experimental tube. In the next 
operation, 25, a small quantity of oxygen wms admitted, but the value for the heat 
evolved per gram of oxygen absorbed was 30-6 K, wdiich is identical w-ith the value 
obtained in Operation J 6 , although in the latter case as much waiter as possible had 
