PROFESSOR THOMAS GRAHAm's SCIENTIFIC WORK. 213 



As regards the removal of hydrogen from palladium by oxygenants, 

 the gas of the charged metal was found to manifest all the chemical 

 activity of hydrogen in the nascent state. Thus it reduced corrosive 

 sublimate to calomel, combined directly with free iodine, converted 

 ferrid into ferro cyanides, destroyed the color of permanganates, &c. 

 Moreover, the spongy metal, charged with hydrogen and exposed to the 

 air, was apt to become suddenly hot, and so completely discharged, by 

 a spontaneous aerial oxidation of its absorbed gas into water ; while the 

 hydrogen of a piece of charged palladium wire was often capable of 

 being set fire to, and of burning continuously along the wire. 



Lastly, the reversal of the position of the palladium plate in the 

 decomposing cell of the battery afforded a most ready means of com- 

 jiletely extracting its hydrogvn. Indeed, for some time after the rever- 

 sal, while hydrogen was being freely evolved from the negative pole, no 

 oxygen was observable on the surface of the palladium plate, now made 

 the positive pole, through its rapid oxygenation of the absorbed 

 hydrogen. 



As regards the extent of the absorption of hydrogen by palladium, it 

 was found, as already indicated, to vary considerably with the physical 

 state of the metal, whether fused, hammered, spongy, or electrolytically 

 deposited, for example. In one case, previously referred to, a specimen 

 of electrolytically deposited palladium, heated to 100'^, and then slowly 

 cooled in a continuous current of hydrogen, was found to occlude 982.14: 

 times its volume of the gas, measured cold. In this case the actual 

 weight of palladium experimented with was 1.0020 gram, and the 

 weight of hydrogen absorbed . 0073 gram, being in the ratio of 

 90,277 per cent, of palladium and 0.723 per cent, of liydrogen. The 

 atomic weight of hydrogen being 1, and that of palladium 100.5, it is 

 observable that the ratio of the weights of the constituents of the charged 

 metal, hydrogen and palladium, approximates to the ratios of their 

 atomic weights. 



In another experiment some palladium wire, drawn from a piece of 

 the fused metal, was charged electrolytically with 935.G7 times its volume 

 of hydrogen. Some idea of these enormous absorptions of hydrogen may 

 be formed by remembering that water at mean temperature absorbs 

 only 782.7 times its volume of that most absorbable of the common gases, 

 ammonia. 



A point of interest with regard to the different quantities of liydrogen 

 absorbable by palladium in its different states is the gradual diminution 

 in the absorptive power of any particular specimen of the metal with 

 each successive charge and discharge of gas in whatever way effected — 

 the absorptive power, however, being partially restorable by subjecting 

 the metal to a welding heat. 



The density of palladium charged with eight or nine hundred times 

 its volume of hydrogen is perceptibly lowered. Owing, however, to a 

 continuous formation of bubbles of hydrogen on the surface of the 



