298 



HYDKOGEN AS A GAS AND AS A METAL, 



ladmm foil, and, liaviug- coimectcd it by a wire with the zinc end of a 

 galvanic cell, to immerse the plate in acidulated water, the positive pole 

 being connected with a plate of platinum likewise immersed in the liquid, 

 hydrogen is immediately set free at the palladium surface, and oxygen 

 at the i)latinum end. The latter gas is given oli in bubl)les from the 

 platinum, whereas the hydrogen is absorbed by the palladium. 



The palladium is capable of thus absorbing about nine hundred times 

 its volume of hydrogen, and this enormous absorption or condensation of 

 hydrogen witbin the pores of the metal takes place without any mate- 

 rial alteration in the color of the palladium, the latter retaining its metallic 

 apxiearance. This, among other circumstances, induced Professor Graham 

 to regard the charged palladium as being a true alloy of palladium with 

 the metal hydrogenium ; for it has been found, that when two metals 

 unite, the compound resulting retains the characters of a metal, whereas 

 this is not the case when a metal and a non-metallic body combine. In 

 order to exhibit this absorption on a large scale, I have arranged the 

 following experiments : 



Pig-.l 



A small glass cell is partially filled with v,-ater, slightly acidulated v.ith 

 sulphuric acid. Into this water a bar of metallic tin is dipped; this bar 

 is of the size shown at T, Fig. 1, and is supported in a horizontal 

 position by means of a varnished wire clamped to the side of the glass 

 cell with the aid of a binding-screw. Having secured T in its position, 

 we now take a slip of rather .stout ])alladinmfoil, about four inches long, 

 and a quarter of an inch wide, and coil it as shown at P ; to the end 

 within the spiral is now attached a fine fiber of glass by means of a 

 minute quantity of cement, and this is so adjusted that the glass shall 

 act as a needle-indicator, as shown in the diagram. The palladium is 

 then attached to the edge of the glass cell by means of a binding-screw 

 and varnished wire. When the cell, so arranged, is placed at D, Fig. 

 2,* the image is projected on the screen, as in Fig. 1. 



* This projection miiy bo iiiostcouveuieiitlye£fcctecl by means of the appar<atiis shown 

 in section at Fi^. 2, and which was arranged for mo by Mr. Yeates, of Dnblin. At A wo 

 have the front of a lantern with the object-glasses removed, the light oxyhydrogeu, 

 oxycalcinm, or any other, having to pass only through the condensers. After passing 

 the condensers, the rays fall on an ordinary mirror, E, suitably inclined to the beam of 



