NATURAL PHILOSOPHY. 181 



IS HYDROGEN GAS A METAL f 



It has been long- suspected that hydrogen would ultimately 

 prove to be a metal. Our readers will also recollect the an- 

 nouncement that during some recent experiments a substance 

 had been discovered, supposed to be the metallic base of hydro- 

 gen. Sdll more recent experiments by Thomas Graham, F.R.S., 

 Master of the British Mint, throw additional light upon this most 

 important subject. 



It has often been maintained on chemical grounds that hydro- 

 gen gas is the vapor of a highly volatile metal. The idea forces 

 itself upon the mind, that XDalladium 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. How 

 far such a view is borne out by the properties of the compound 

 substance in question, will appear by the following examination 

 of the properties of what, assuming its metallic character, would 

 fairly be named hydrogenium. 



The density of palladium, when charged with 800 or 900 

 times its volume of hydrogen gas, is perceptibly lowered, but the 

 change cannot be measured accurately by the ordinary method 

 of immersion in water, owing to a continuous evolution of minute 

 hydrogen bubbles, which appear to be determined by contact with 

 the liquid. However, the linear dimensions of the charged palla- 

 dium are altered so considerably, that the difference admits of 

 easy measurement, and furnishes the required density by calcu- 

 lation. Palladium, in the form of wire, is readily charged with 

 hydrogen, by evolving that gas upon the surface of the metal in 

 a galvanometer containing dilute sulphuric acid, as usual. The 

 length of the wire, before and after a charge, is found by stretch- 

 ing it on both occasions bj' the same moderate weight, such as 

 will not produce permanent distention over the surface of a fiat, 

 graduated measure. The measure was graduated to hundredths 

 of an inch, and by means of a vernier, the divisions could be 

 riuid to thousandths. The distance between two fine cross lines 

 marked upon the surface of the wire near each of its extremities 

 was observed. 



The wire had been drawn from welded palladium, and was 

 hard and elastic. The diameter of the wire was 0.462 millimetres ; 

 its specific gravity was 15.38, as determined with care. The wire 

 was twisted into a loop at each end, and the mark made near 

 each loop. The loops were varnished so as to limit absorption of 

 gas by the wire to the measured length between the two marks. 

 To straighten the wire, the loop was fixed, and the other con- 

 nected with a string passing over a pulley and loaded with 1.5 

 kilogrammes, a weight sufficient to straighten the wire without 

 occasioning any undue strain. The wire was charged with hy- 

 drogen by ranking it the negative electrode of a small Bunsen's 

 battery, consisting of two cell-^, each of half a litre in capacity. 

 The positive electrode was a thick, plantinum wire, placed side 



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