HYDROGENIUM ; THE RELATION OF HYDROGEN TO PALLADIUM:. 155 
paramagnetic and diamagnetic classes. But magnetism is so liable to extinction under 
tae influence of heat, tha.t the magnetism of a metal may very possibly disappear entirely 
when it is fused or vaporized, as appears to be the case with hydrogen in the form of gas 
As palladium stands high in the series of the paramagnetic metals, hydrogenium must be 
allowed to rise out of that class, and to take place in the strictly magnetic group with 
iron, nickel, cobalt, chromium, and manganese. 
5. Palladium ivith Hydrogen at a high Temperature .—The ready permeability of 
heated palladium by hydrogen gas would imply the retention of the latter element by 
the metal even at a bright red heat. The hydrogenium must, in fact, travel through the 
palladium by cementation, a molecular process which requires time. The first attempts 
o arrest hydrogen in its passage 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 examined 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 sud¬ 
denly cooling the metal in water, a small portion of hydrogen was found locked up in 
the metal. A volume of metal amounting to 0*062 cubic centim., gave 0*080 cubic 
centim. of hydrogen; or, the gas, measured cold, was 1*306 times 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 hydrogen appears, therefore, to depend 
on absorption, and not to require the assumption of anything like porosity in their struc¬ 
ture. 
The highest velocity of permeation observed was in the experiment where four litres 
of hydrogen (3992 cub. centims.) per minute passed through a plate of palladium 1 millim. 
in thickness, 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 millimetres per minute. 
6. Chemical Properties. —Th^ 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. Stanislas Meunier failed in discovering 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. Hydrogen (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 consider¬ 
able 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 inquiry 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 both substances are solid, metallic, 
and of a white aspect. That the alloy contains about 20 volumes of palladium united 
with a volume of hydrogenium ; and that the density of the latter is about 2, a little 
higher than magnesium, to which hydrogenium may be supposed to bear some analogy. 
That hydrogenium has a certain amount of tenacity, and possesses the electrical conduc¬ 
tivity of a metal. And finally, that hydrogenium takes its place among magnetic 
metals. The latter fact may have its bearing upon the appearance of hydrogenium in 
meteoric iron, in association with certain other magnetic elements. 
I cannot close this paper without taking the opportunity to return my best thanks to 
Mr. W. C. Roberts, for his valuable co-operation throughout the investigation. 
* Proceedings of the Royal Society, 1868, p. 426. 
