Mr. T. Graham on Hydrogenium. 461 



with platinum, a metal of its own class, and gave an alloy consisting, 

 according to analysis, of 76*03 parts of the former and 23*97 parts 

 of the latter. This alloy was very malleable and ductile ; its specific 

 gravity was 12*64. Like pure palladium, it absorbed hydrogen, 

 evolved on its surface in the acid fluid of the galvanometer, with 

 great avidity. 



A wire 601*845 millims. in length (23*69 inches) was increased 

 to 618*288 millims., on occluding 701*9 volumes of hydrogen gas 

 measured at 0° C. and 0*760 barom. This is a linear elongation of 

 16*443 millims. (0*6472 inch), or 2*732 on a length of 100. It 

 corresponds with a cubic expansion of 8*423 volumes on 100 vo- 

 lumes ; and the product may be represented — 



In volume. 



Fixed metals 100*000 or 92*225 



Hydrogenium 8*423 or 7' 77 5 



108*423 or 100*000 



The elements for the calculation of the density of hydrogenium 

 are the following, the assumption being made as formerly, that 

 the metals are united without condensation : — 



Original weight of the wire 4*722 grms. 

 Original volume of the wire 0*373 cub. centim. 

 Volume of the hydrogen extracted 264*5 cub. centims. 

 Weight of the hydrogen extracted, by calculation, 0*0237 grm. 



The volume of the hydrogenium will be to the volume of the 

 wire (0*373 cub. centim.) as 100 is to 8*423— that is, 0*03141 

 cub. centim. Finally, dividing the weight of the hydrogenium by 

 its bulk, 0*0237 by 0*03141, the density of hydrogenium is found 

 to be 0*7545. 



On expelling all hydrogen from the wire at a red heat, the 

 latter returned to its first dimensions as exactly as could be mea- 

 sured. The platinum present appears to sustain the palladium, so 

 that no retraction of that metal is allowed to take place. This alloy 

 therefore displays the true increase of volume following the acqui- 

 sition of hydrogenium, without the singular complication of the 

 retraction of the fixed metal. It now appears clear that the retrac- 

 tion of pure palladium must occur on the first entrance of hydrogen 

 into the metal ; the elongation of the wire due to the hydrogenium 

 is negatived thereby to the extent of about one half, and the ap- 

 parent bulk of the hydrogenium is reduced to the same extent; 

 hydrogenium came in consequence to be represented of double its 

 true density. 



The compound alloy returns to its original density (12*64) upon 

 the expulsion of the hydrogen, showing that hydrogen leaves with- 

 out producing porosity in the metal. No absorptive power for 

 vapours, like that of charcoal, was acquired. 



A wire of the present alloy, and another of pure palladium, were 

 charged with hydrogen, and the diameters of both measured by a 

 micrometer. The wire of alloy increased sensibly more in thickness 

 than the pure palladium, about twice as much ; the reason is, that 



