﻿Hydrogen to Palladium, 



125 



Volume of palladium wire ... 0*0949 cub. centim. 



Volume of occluded hydrogen gas . 84*3 cub. centims. 



Weight of same 0*007553 grin. 



Volume of hydrogenium .... 0'003820cub. centim* 



These results give by calculation 



Density of hydrogenium .... 1*977. 



It was necessary to assume in this discussion that the two 

 metals do not contract nor expand, but remain of their proper 

 volume on uniting. Dr. Matthiessen has shown that in the for- 

 mation of alloys generally the metals retain approximately their 



original densities*. 



In the first experiment already described, probably the maxi- 

 mum absorption of gas by wire, amounting to 935*67 volumes, 

 is attained. The palladium may be charged with any smaller 

 proportion of hydrogen by shortening the time of exposure to 

 the gas (329 volumes of hydrogen were taken up in twenty mi* 

 nutes), and an opportunity be gained of observing if the density 

 of the hydrogenium remains constant, or if it varies with the 

 proportion in which hydrogen enters the alloy. In the follow- 

 ing statement, which includes the three experiments already re- 

 ported, the essential points only are produced : — 



Table. 



Volumes of 

 hydrogen 

 occluded. 



Linear expansion in 

 millimetres. 



Density of 

 hydrogenium. 



From 



To 



329 



462 



487 

 745 

 867 

 888 

 936 



496-189 

 493 040 

 370-358 

 305-538 

 488-976 

 556-185 

 609144 



498-552 

 496-520 

 373126 

 511-303 

 495-656 

 563-652 

 618-923 



2055 

 1-930 

 1-927 

 1-917 



1-898 

 1-977 

 1-708 



If the first and last experiments only are compared, it would 

 appear that the hydrogenium becomes sensibly denser when the 

 proportion of it is small, ranging from 1*708 to 2*055. But the 

 last experiment of the Table is perhaps exceptional ; and all the 

 others indicate considerable uniformity of density. The mean 

 density of hydrogenium, according to the whole experiments, ex- 

 cluding that last referred to, is 1*951, or nearly 2. This unifor- 

 mity is in favour of the method followed for estimating the den- 

 sity of hydrogenium. 



On charging and discharging portions of the same palladium 



* Philosophical Transactions, 1860, p. 1/7. 



