1869.] 



of Hydrogen to Palladium. 



217 



current from a battery. The absorption rose thereafter to 425 volumes 

 of hydrogen, and in a second experiment to 422*5 volumes. 



The wire becomes fissured longitudinally, acquires a thready structure, and 

 is much disintegrated on repeatedly losing hydrogen, particularly when 

 the hydrogen has been extracted by electrolysis in an acid fluid. The pal- 

 ladium in the last case is dissolved by the acid to some extent. The metal 

 appeared, however, to recover its full power to absorb hydrogen, now con- 

 densing upwards of 900 volumes of gas. 



The effect upon its length of simply annealing the palladium wire by 

 exposure in a porcelain tube to a full red heat, was observed. The wire 

 measured 556-0/5 millims. before, and 555*8/5 millims. after heating; or 

 a minute retraction of 0*2 millim, was indicated. In a second annealing 

 experiment, with an equal length of new wire, no sensible change whatever 

 of length could be discovered. There is no reason, then, to ascribe the 

 retraction after hydrogen, in any degree, to the heat applied when the gas 

 is expelled. Palladium wire is very slightly affected in physical properties 

 by such annealing, retaining much of its first hardness and elasticity. 



2. Tenacity. — A new palladium wire, similar to the last, of which 100 

 millims. weighed 0*1987 grm., was broken, in experiments made on two 

 different portions of it, by a load of 10 and of 10*17 kilogrammes. Two 

 other portions of the same wire, fully charged with hydrogen, were broken 

 by 8*18, and by 8*27 kilogrammes. Hence we have — 



Tenacity of palladium wire 100 



Tenacity of palladium and hydrogen 81*29 



The tenacity of the palladium is reduced by the addition of hydrogen, but 

 not to any great extent. It is a question whether the degree of tenacity 

 that still remains is reconcileable with any other view than that the second 

 element present possesses of itself a degree of tenacity such as is only found 

 in metals. 



3. Electrical Conductivity. — Mr. Becker, who is familiar with the practice 

 of testing the capacity of wires for conducting electricity, submitted a palla- 

 dium wire, before and after being charged with hydrogen, to trial, in com 

 parison with a wire of German silver of equal diameter and length, at 10°* 5. 

 The conducting-power of the several wires was found as follows, being re- 



ferred to pure copper as 100 : — 



Pure copper 100 



. Palladium 8*10 



Alloy of 80 copper + 20 nickel 6*63 



Palladium + hydrogen 5*99 



A reduced conducting-power is generally observed in alloys, and the charged 

 palladium wire falls 25 per cent. But the conducting-power remains still 

 considerable, and the result may be construed to favour the metallic character 

 of the second constituent of the wire. Dr. Matthiessen confirms these 

 results. 



VOL. XVII. R 



