182 ANNUAL OF SCIENTIIIC DISCOVERr. 



by side with the palladium wire, and extending the whole length 

 of the hitter, within a tall jar tilled with dilute suiphuric aiid. 

 The palladium wire had, in consi'quenc;e, hydrogen carried to its 

 surface for a jjeriod of ope and a half hours. A longer exposure 

 was found not to add sensibly to the charge of hydrogen acquircjd 

 by the wire. The wire was again measured and the increase 

 in length noted. Finall}', the wire, being dried with a cloth, was 

 divided at the murks, and the charged portion heated in a lotig 

 narrow glass tube kept vacuous by a Sprengel aspirator. The 

 whole occluded hydrogen was thus eolleeteil and measured ; its 

 volume is reduced by calculation to Bar. 7G0 m.m., and Therm. » 

 0°C. 



The original length of the palladium wire e:4posed was GOO. 144 

 m.m. (23.982 inches) and its weight l.G8o2 grm. The wire re- 

 ceived a charge of hydrogen amounting to 9o6 times its volume, 

 measuring 128 c.c, and therefore weighing 0.01147 grm. 

 When the gas was ultimately expelled, the loss as ascertained by 

 direct weighing was 0.011G4 grm. The charged wire measured 

 G18.923 m.m., showing an increase in length of 9.779 m.m. (0- 

 .385 inch.) The increase in linear dimensions is from 100 to 101- 

 .G05; and in cubic capacity, assuming the exixansion to be equal 

 in all directions, from 100 to 104.908. Supposing the two metals 

 united without any change of volume, the alloy may therefore be 

 said to be composed of — 



By volume. 



Palladium lUO or 95.32 



Hydrogoniura 4.908 or 4.G8 



J 



104.908 100 



The expansion which the palladium undergoes appears enormous 

 if viewed as a change of bulk in the metal only, due to any con- 

 ceivable physical force, amounting as it does to 16 times the 

 dilatation of palladium when heated from 0° to 100° C. The 

 density of the charged wire is reduced by calculation from 12.3 

 to 11.79. Again, as 100 is to 4.91, so the volume of the palladium, 

 0.1368 c.c, is to the volume of the hydrogenium 0.00G714 c.c. 

 Finally, dividing the weight of the hydrogenium, 0.01147 grm., 

 by its volume in the alloy, 0.00G714 c.c, we find 



Density of hydrogenium, 1.708 



The density of hydrogenium, then, appears to approach that 

 of magnesium, 1.743, by this first experiment. 



Further, the expulsion of hydrogt'n from the wire, however 

 caused, is attended with an extraordinary contraction of the lat- 

 ter. On expelling the hydrogen by a moderate heat, the wire 

 not only receded to its original length, but fell as much below 

 that zero as it had previously ri^dcMi above it. The palladium wire 

 first measuring G09. 144 m.m., and which Increa.sed 9.77 m.m., 

 was ultimately reduced to 590.444 mm., and contracted 9.7 

 m.m. The wire is peimanently shortened. The density of the 



