﻿On the Relation of Hydrogen to Palladium. 123 



capacity. The positive electrode was a thick platinum wire 

 placed side by side with the palladium wire, and extending the 

 whole length of the latter within a tall jar filled with dilute sul- 

 phuric acid. The palladium wire had, in consequence, hydrogen 

 carried to its surface, for a period of 1^ hour. A longer exposure 

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

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

 length noted. Finally the wire, being dried with a cloth, was 

 divided at the marks, and the charged portion heated in a long 

 narrow glass tube kept vacuous by a Sprengel aspirator. The 

 whole occluded hydrogen was thus collected and measured ; its 

 volume is reduced by calculation to Barom. 760 inillims., and 

 Therm. 0° C. 



The original length of the palladium wire exposed was 609' 14.4 

 millims. (23*982 inches), and its weight 1*6832 grm. The wire 

 received a charge of hydrogen amounting to 936 times its volume, 

 measuring 128 cubic centims., and therefore weighing 0*01147 

 grm. When the gas was ultimately expelled, the loss as ascer- 

 tained by direct weighing was 0*01164 grm. The charged wire 

 measured 618*923 millims., showing an increase in length of 

 9*779 millims. (0*385 inch). The increase in linear dimensions 

 is from 100 to 101*605, and in cubic capacity, assuming the 

 expansion 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 ... 100 or 95*32 



Hydrogenium . . 4*908 or 4*68 



104*908 100 

 The expansiou 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 sixteen 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 palla- 

 dium, 0*1358 cubic centim., is to the volume of the hydrogenium 

 0*006714 cubic centim. Finally, dividing the weight of the hy- 

 drogenium, 001 147 grm., by its volume in the alloy, 0*0067i4 

 cubic centim., 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 hydrogen from the wire, however 

 caused, is attended with an extraordinary contraction of the latter. 

 On expelling the hydrogen by a moderate heat, the wire not only 



