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VII. — On the Electrical Properties of Hydrogenised Palladium, By Cargill G. 

 Knott,D.Sc. (Edin.),F.RS.E., Professor of Physics, Imperial University, 

 Tokay o, Japan. (Plate XI.) 



(Despatched to Royal Society of Edinburgh, May 25, 1886. Read 19th July 1886.) 



In the following paper I desire to place on record the results of certain 

 experiments which have lately engaged my attention. The facts established 

 are, so far as I am aware, novel and in themselves interesting. 



Many of the physical properties of hydrogenised palladium or hydrogenium 

 have been carefully studied by Graham, Dewar, and others ; but no one seems 

 to have called attention to its thermoelectric peculiarities, or to have made a 

 special study of its electrical resistance. These two inquiries form the subject 

 of this paper. Throughout I shall use, for brevity's sake, the name Hydrogenium, 

 which was applied by Graham to the fully-saturated form. Here, however, it 

 is applied generally to any alloy of the two substances, without any regard to a 

 possible chemical compound of definite molecular constitution. The paper 

 naturally divides itself into two sections — the first part relating to the electrical 

 resistance, the second part to the thermoelectric properties. 



Electrical Eesistance of Hydrogenium. 



The steady increase of the resistance of hydrogenium with the charge of 

 hydrogen was noticed by Dewar;* and further details were given by myself 

 in a short paper published a few years ago.t There I obtained a resistance of 

 1*518 for fully-saturated hydrogenium, of which the originally pure palladium 

 wire had a resistance of unity. In the present inquiry I have easily obtained a 

 much greater increase of resistance — such as 1-634, 1*7775, and even as much 

 as 1*83. Whether this may be a result of impurities being present in the acid 

 which was used as the electrolyte, I cannot say. It may be noted, however, 

 that the palladium wire itself was obtained in Paris, and was guaranteed to be 

 very pure indeed. 



The main purpose of the present investigation was to study the temperature 

 characteristics of the resistance of hydrogen-charged palladium. Throughout 

 each series of experiments the same palladium wire was used, the hydrogen 



* Trans. Roy. Soc. Edin., vol. xxvii. t Proe. Roy. Soe. Edin., 1882-83. 



VOL. XXXIII. PART I. 2 A 



