OCCLUSION OF HYDROGEN AND OXYGEN BY PALLADIUM. 



125 



Assuming, as was necessary in the case of the corresponding experiment on 

 platinum black (q.v., 'Phil. Trans.,' A, 1897, vol. 190, p. 149), that no appreciable 

 heat change is involved in the mere wetting of the palladium by the water formed, 

 and knowing the total heat of the reaction, the heat of formation of water, the heat 

 of occlusion of the hydrogen, and the quantity of oxygen removed, we can calculate 

 the heat absorbed on its removal. 



The results obtained in three independent experiments are given below in tabular 

 form. The amounts of hydrogen occluded and oxygen removed are expressed in 

 cubic centimetres, volumes (Pd. bk. = 1), and grams ; and it will be seen that there is 

 a very satisfactory agreement among themselves of the values representing the number 

 of volumes of hydrogen occluded and the number of volumes of oxygen removed. 



CALORIMETRIC Experiments on the Absorption of Oxygen by Palladium Black. 



The three values of the heat absorbed per gram of oxygen removed, or, what 

 amounts to the same thing, the heat evolved per gram of oxygen absorbed, are thus 

 + 11-9, + 12-0, and + 11'2 K., whilst the mean of the three is + 117 K. This 

 number, referred to 16 grams of oxygen, becomes + 187 K.(+ 18700 gram calories). 



From the nature of these experiments it is difficult to say within what limits of 

 error this number may be taken as correctly representing the heat of absorption of 

 oxygen in palladium black. As far as such measurements go, however, the agreement 

 between the individual numbers may be said to be satisfactory. 



