On Hydrogenium. 45 



place, and there is also, as in the former example of the 

 formation of common salt, a measurable increase in the size 

 and in the weight of the product. Graham has investigated 

 these changes with such precision and minuteness as to show 

 exactly what takes place. The palladium can absorb into 

 its substance not less than 936 times its volume of hydrogen 

 gas ; that is to say, a small disc of the solid palladium 

 of the diameter of this tube (showing a glass tube over 

 three feet in length), and 25 th of an inch thick, something 

 nearly approaching the size of this little gem of a medal, 

 would condense within its atoms the whole contents of this 

 tube of hydrogen gas. If we regard the little disc as a 

 piston closely lifting the tube, and if we regard this con- 

 densation of the hydrogen as the result of a pressure 

 exerted from without, it would require a force equal to more 

 than eight thousand atmospheres, a pressure of over 55 tons 

 on the inch, to force this piston down in the tube until the 

 palladium and condensed hydrogen together occupied the 

 same bulk as they do in the alloy, by virtue of the force of 

 attraction exerted from within. 



When the combination of the palladium and hydrogenium 

 is effected, the resulting alloy is of larger bulk than a very 

 great increase of temperature of the palladium itself would 

 occasion ; but the palladium itself in the alloy is actually 

 squeezed into a smaller space at the time of combination. 

 This is shown by its occupying less than its original space, 

 if the hydrogenium be distilled out of it, and by certain 

 experiments, the results of which prove that this diminu- 

 tion of bulk does not take place at the time of the expulsion 

 of the hydrogenium. 



That the combination is of the nature of an alloy is 

 deduced from measurements of its tenacity and electrical 

 conductivity, both very near to those of pure palladium, 

 and, which is very remarkable, by the hydrogenium in the 

 alloy proving measurably a magnetic metal. The two con- 

 stituents stand in atomic proportions, and the solidified 

 hydrogen, the hydrogenium, has chemical properties differ- 

 ing from those of hydrogen gas, differing very much as the 

 properties of ozone do from those of oxygen. From a 

 solution of corrosive sublimate, the alloy of hydrogenium 

 and palladium precipitates mercury and calomel, a change 

 which hydrogen itself is quite incapable of effecting. A mix- 

 ture of hydrogen and chlorine gas remains permanently 

 unchanged as long as it is kept in the dark ; but exposed to 



