1869.] 



Mr. T. Graham on Hydrogenium. 



501 



may be detailed. This wire, which was new, took up a full charge of 

 hydrogen, namely 956*3 volumes, and increased in length from 609*585 

 to 619*354 millims. The elongation was therefore 9*769 millims. With 

 the expulsion of the hydrogen afterwards, the wire was permanently 

 shortened to 600*115 millims. It thus fell 9'470 millims. below its normal 

 or first length. The elongation and retraction are here within 0*3 millim. 

 of equality. The two changes taken together amount to 19*239 millims., 

 and their sum represents the increase of the wire in length due to the 

 addition of hydrogenium. It represents a linear expansion of 3*205 

 on 100, with a cubic expansion of 9*82/ on 100. The compositon of the 

 wire comes to be represented as being, 



In volume. 



Palladium 100*000 or 90*895 



Hydrogenium 9*82/ or 9*105 



109*827 or 100*000 



The specific gravity of the palladium was 12*3, the weight of the wire 

 1*554 grm., and its volume 0*126 cub. centim. The occluded hydrogen 

 measured 120*5 cub. centims. The weight of the same would be 0*0108 

 grm., and the volume of the hydrogenium 0*012382 cub. centim. (100: 

 9*827 : : 0*126 : 0*01238). The density of the hydrogenium is therefore 



°- Q1Q8 =0*872. 

 0*01238 



This is a near approach to the preceding result, 0*854. Calculated on the 

 old method, the last experiment would give a density of 1*708. 



It was incidentally observed on a former occasion that palladium 

 alloyed with silver continues to occlude hydrogen. This property is now 

 found to belong generally to palladium alloys, when the second metal does 

 not much exceed one half of the mixture. These alloys are all enlarged in 

 dimensions when they acquire hydrogenium. It was interesting to per- 

 ceive that the expansion was greater than happens to pure palladium 

 (about twice as much), and that, on afterwards expelling the hydrogen by 

 heat, the fixed alloy returned to its original length without any further 

 shortening of the wire. The embarrassing retraction of the palladium 

 has, in fact, disappeared. 



The fusion of the alloys employed was kindly effected for me by 

 Messrs. Matthey and Sellon, when the proportion of palladium was con- 

 siderable, by the instrumentality of M. Deville's gas-furnace, in which 

 coal-gas is burned with pure oxygen — or by means of a coke-furnace 

 when the metals yielded to a moderate temperature. The alloy was 

 always drawn out into wire if possible, but if not sufficiently ductile, it 

 was extended by rolling into the form of a thin ribbon. The elongation 

 caused by the addition of hydrogenium was ascertained by measuring the 

 wire or ribbon stretched over a graduated scale, as in the former ex- 

 periments. 



