Mr. T. Graham on Hydrogenium. 463 



similar, namely 468 volumes, and was not increased by protracting 

 the exposure of the wire for the long period of twenty hours. There 

 can be little doubt, then, of the uniformity of the hydrogenium com- 

 bination, the volumes of gas occluded in the three experiments being 

 464*2, 4G3 , 7, and 468 volumes. The linear expansion was 1*9 on 

 100 in the third experiment, and therefore similar also to the prece- 

 ding experiments. 



The hydrogenium may be supposed to be in direct combination 

 with the palladium only, as gold by itself shows no attraction for the 

 former element. In the first experiment the hydrogenium is in the 

 proportion of 0*3151 to 100 palladium and gold together. This 

 gives 0*3939 hydrogenium to 100 palladium ; while a whole equiva- 

 lent of hydrogenium is 0*939 to 100 palladium*. The hydrogenium 

 found is by calculation 0*4195 equivalent, or 1 equivalent hydroge- 

 nium to 2*383 equivalents palladium, which comes nearer to 2 equi- 

 valents of the former with 5 of the latter than to any other proportion. 



To ascertain the smallest proportion of gold which prevents retrac- 

 tion, an alloy was made by fusing 7 parts of that metal with 93 parts 

 of palladium, which had a specific gravity of 13*05. The button 

 was rolled into a thin strip and charged with hydrogen by the wet 

 method. An occlusion of 585*44 volumes of gas took place, with a 

 linear expansion of 1*7 on 100. A retraction followed to nearly 

 the same extent on afterwards expelling the hydrogen by heat. 



With another alloy, produced by fusing 10 of gold with 90 of pal- 

 ladium, the occlusion of gas was 475 volumes, the linear expansion 

 1*65 on 100. The retraction on expelling the gas afterwards was 

 extremely slight. To nullify the retraction of the palladium, about 

 10 per cent, of gold appears therefore to be required in the alloy. 



Another alloy of palladium of sp. gr. 13*1, and containing 24*79 

 per cent, of gold, underwent no retraction on losing hydrogen, as 

 already stated. 



The presence of so much gold in the alloy as half its weight did 

 not materially reduce the occluding power of the palladium. Such 

 an alloy was capable of holding; 459*9 times its volume of hydrogen, 

 with a linear expansion of 1*67 per cent. 



3. Palladium, Silver, and Hydrogenium. — The occluding power 

 of palladium appeared to be entirely lost when that metal was alloyed 

 with much more than its own weight of any fixed metal. Palladium 

 alloys containing 80, 75, and 70 per cent, of silver occluded no hy- 

 drogen whatever. 



With about 50 per cent, of silver, palladium rolled into a thin 

 strip occluded 400*6 volumes of hydrogen. It expanded 1*64 part 

 in 100 in length, and returned to its original dimensions without 

 retraction upon the expulsion of the gas. The specific gravity of 

 this silver-palladium alloy was 11*8 ; the density of the hydrogenium 

 0*727. 



An alloy which was formed of 66 parts of palladium and 34 parts 



of silver had the specific gravity 11*45. It was drawn into wire 



and found to absorb 511*37 volumes of hydrogen. The length of 



the wire increased from 609*601 to 619*532 millims. This is a linear 



* 11=1; Pd= 106-5. 



