﻿130 On the Relation of Hydrogen to Palladium. 



through the red-hot metal were made by transmitting hydrogen 

 gas through a metal tube of palladium with a vacuum outside, 

 rapidly followed by a stream of carbonic acid, in which the 

 metal was allowed to cool. When the metal was afterwards ex- 

 amined in the usual way, no hydrogen could be found in it. 

 The short period of exposure to the carbonic acid seems to have 

 been sufficient to dissipate the gas. But on heating palladium 

 foil red-hot in a flame of hydrogen gas, and suddenly cooling 

 the metal in water, a small portion of hydrogen was found 

 locked up in the metal. A volume of metal amounting to O0G2 

 cubic centim., gave 0*080 cubic centim. of hydrogen ; or, the 

 gas, measured cold, was 1*306 time the bulk of the metal. 

 This measure of gas would amount to three or four times the 

 volume of the metal at a red heat. Platinum treated in the 

 same way appeared also to yield hydrogen, although the quantity 

 was too small to be much relied upon, amounting only to 0*06 

 volume of the metal. The permeation of these metals by hy- 

 drogen appears therefore to depend on absorption, and not to 

 require the assumption of anything like porosity in their stucture. 



The highest velocity of permeation observed was in the expe- 

 riment where four litres of hydrogen (3992 cubic centims.) per 

 minute passed through a plate of palladium 1 millim. in thick- 

 ness, and calculated for a square metre in surface, at a bright 

 red heat, a little short of the melting-point of gold. This is a 

 travelling movement of hydrogen through the substance of the 

 metal with the velocity of 4 millims. per minute. 



The Chemical Properties of hydrogenium also distinguish it 

 from ordinary hydrogen. . The palladium alloy precipitates 

 mercury and calomel from a solution of the chloride of mercury 

 without any disengagement of hydrogen; that is, hydrogenium 

 decomposes chloride of mercury, while hydrogen does not. 

 This explains why M. Stanislaus Meunier failed to discover 

 the occluded hydrogen of meteoric iron by dissolving the latter 

 in a solution of chloride of mercury • for the hydrogen would 

 be consumed, like the iron itself, in precipitating mercury. Hy- 

 drogen (associated with palladium) unites with chlorine and 

 iodine in the dark, reduces a persalt of iron to the state of 

 protosalt, converts red prussiate of potash into yellow prussiate, 

 and has considerable deoxidizing powers. It appears to be the 

 active form of hydrogen, as ozone is of oxygen. 



The general conclusions which appear to flow from this in- 

 quiry are that in palladium fully charged with hydrogen (as in 

 the portion of palladium wire now submitted to the Royal 

 Society) there exists a compound of palladium and hydrogen in 

 a proportion which may approach to equal equivalents*; that 



* Proceedings of the Koyal Society, 1868, vol. xvi. p. 425. fPhil. Mag. 

 July 1868. p. 66.] * L 



