D. CHEMISTRY AND METALLURGY. 199 



D. CHEMISTRY AND METALLURGY. 



HYDROGENOUS PALLADIUM. 



The combination of hydrogen with palladium, first discov- 

 ered by Graham, and termed by him occlusion, has been gen- 

 erally supposed to indicate the formation of a true alloy be- 

 tween the metals palladium and hydrogenium. This opinion 

 was stated by Graham, who proved that the density of pal- 

 ladium, when it conceals from eight to nine hundred volumes 

 of hydrogen within itself, is sensibly inferior to that of the 

 pure metal, while its tenacity and electric conductivity are 

 diminished and the magnetism augmented. This subject has 

 been lately investigated by Messrs. Troost and Hautefeuille, 

 who have shown that the phenomenon is more complex than 

 has hitherto been supposed; that in fact palladium forms 

 with hydrogen a definite compound, whose formula is two 

 molecules of the former and one of the latter. This combi- 

 nation itself, once formed, can then dissolve hydrogen gas aft- 

 er the manner of platinum, and in quantity variable with its 

 physical state. This property of the new compound explains 

 the difference between the numerical results obtained by 

 Graham, according as he employed palladium wire or spongy 

 palladium. This hydrogenous palladium, together with cer- 

 tain similar combinations of potassium and sodium with hy- 

 drogen, forms a series parallel to that combination of copper 

 with hydrogen called by Wurtz the hydride of copper. 



THE OCCLUSION OF HYDROGEN BY IRON. 



At a recent meeting of the Philosophical Society of Man- 

 chester, England, Mr. Johnson exhibited some iron and steel 

 wire whose nature had been so changed that, from being ex- 

 ceedingly tough, it had become short and brittle, while its 

 weight was increased; and a fresh fracture at any point ap- 

 peared, when treated chemically, to show that the chemical 

 constitution of the iron had undergone a remarkable change. 

 Professor Osborne Reynolds having made a careful examina- 

 tion of this wire, seems to have established the fact that free 

 hydrogen had entered into and combined vyith the iron and 



