CHEMISTRY. 



HYDROGENIUM. 



Some years since, Deville and Troost discovered that hydrof^en 

 passed somewhat readily througli platinum at a higli temjiera- 

 tnre, and hiterGraham discovered the property of palladium even 

 at low temperatures of taking up and retaining within itself a 

 large proportion of hydrogen. 



It has often been maintained, on chemical grounds, tliat hydro- 

 gen gas is the vapor of a highty volatile metal. Graham, in two 

 papers read before the Royal Society,* details a series of experi- 

 ments made by him, from vvhich he concludes that *' palladium, 

 with its occluded hydrogen, is simply an alloy of this volatile 

 metal, in which the volatility of the one element is restrained by 

 its union with the other, and which owes its metallic aspect 

 equally to both constituents." Assuming that hydrogen does 

 really thus exist in a metallic state, he calls the metal hydro- 

 genium. 



The jxilladium was employed in the form of wire, and was 

 charged with hydrogen by making it the negative electrode of 

 a small Bunsen battery ; the positive electrode consisted of a 

 j)latinum wire extending by the side of the palladium wire in a 

 jar of acidulated water. In this way the palladium wire occluded 

 an amount of hydrogen equal to 800 or 900 times its own vol- 

 ume. , 



Densiiy. — The density of palladium when charged with 800 or 

 900 times its volume of hydrogen is perceptibly lowered. The 

 density of the alloy cannot be measured in water in the usual 

 manner, as the mere immersion in water determines the escape 

 ofhvdrogen. It was therefore estimated, assuming that th(! two 

 metals united without condensation, by measuring the wire un- 

 der an equal tension, before and after charging it .with hydro- 

 gen. 



The hydrogen was then exhausted by a Sprengel aspirator and 

 the volume measured. 



It was found, on exhausting the hydrogen, that the palladium 

 wire had decreased in length by an amount nearly equal to its 

 increase over its original length. Supposing th(! increase of vol- 

 ume <lue to the hydrogenium to be represented ijy the sum of 

 the elongation and the retraction, the density of hydrogenium 

 calculated from a number of experiments would be in the neigh- 

 borhood of .85. 



•Printed in full in tho"Chom. News," Vol. xix., p. 52, and Vol. xx., p. IG. 



