On Hydrogenium. 43 



combinations by metals in another class of changes. By- 

 elevation of temperature all metals can be reduced to the 

 fluid condition, and many are easily converted into invisible 

 vapours. Even silver has been distilled, as water or spirit 

 is distilled, although at a much higher temperature. Mer- 

 cury is an instance of a metal fluid at common tempera- 

 tures, but which can be frozen into a solid ; and there is an 

 alloy of sodium and potassium which is also a fluid under 

 normal conditions. Why then should we not have a metal 

 which is gaseous under ordinary circumstances ? There 

 appears to be no valid reason ; but until Dr. Graham showed 

 us this alloy of palladium and the consolidated hydrogen, 

 we have never been able to catch a glimpse of hydrogen in 

 either the liquid or solid form. Many gases liquify under 

 intense pressure, and become even solid when the combined 

 effects of both pressure and cold are employed ; but 

 hydrogen has resisted every attempt to squeeze it into a 

 liquid by pressure from without ; and it was not until 

 Graham employed force in a different direction that any 

 positive result of the compression of hydrogen was 

 obtained. 



Graham's results were obtained by making palladium the 

 negative pole or cathode of a voltaic battery, decomposing 

 water. In the arrangement, the hydrogen, one of the con- 

 stituents of the resolved water, is set free in contact with 

 the palladium, and as the latter has an affinity for the 

 hydrogen, besides other physical peculiarities favourable to 

 the fixation of the gas, the hydrogen, instead of rising in 

 bubbles and escaping through the fluid, passes into the 

 palladium. The h^^drogen does not pass into the pores of 

 the metal, if we understand the word pore in its everyday 

 sense. It does not pass into any crevices or tubular 

 openings into which moisture could enter, but it penetrates 

 in the most intimate way the substance of the palladium, 

 a metal denser than steel, having a specific gravity of 

 12 08, in fact, more than half as heavy again as cast-steel. 

 The hydrogen passes into the palladium much as 

 carbon is carried into the substance, between the atoms, of 

 iron during the process of steel-making by cementation. 

 The hydrogen passes in and is compressed, not' by a pressure 

 from without, but by an attractive force exerted from 

 within. By this force the hydrogen is drawn to the inner- 

 most parts of the plate of palladium, and it is compressed 

 and solidified into what shows strong evidence of being a 



