114 DRS. L. MONO, W. RAMSAY, AND J. SHIELDS, ON THE 



more or less spongy nature, due to the transition through the state of oxide, and 

 consequently we should expect it to behave more like the sponge. 



Most of the palladium employed by other observers has probably been subjected 

 to this treatment, which possibly explains the readiness with which in most instances 

 it takes up hydrogen. There is also evidence, from other sources, that new palla- 

 dium foil possesses a lower absorption power for hydrogen. For example, a portion 

 of new palladium foil, examined by GRAHAM ('Researches,' p. 268), and believed to 

 be from fused metal, occluded only 68 volumes of hydrogen. This is ascribed by 

 GRAHAM to the fact that the metal had been fused. " An inferior absorbing power 

 for hydrogen appears to be connected in both platinum and palladium with the 

 fusion of the metal." GRAHAM'S explanation is quite consistent with the view here 

 put forward, for the fusion of the metal would simply produce (only, perhaps, in a 

 more perfect way) the same effect as a thorough welding or rolling. 



The foil examined by us had not been fused, but it persistently refused to occlude 

 hydrogen in any quantity. 



After it had been submitted to the preceding operations it was ignited several 

 times in the blowpipe flame, rolled up, reignited, and introduced hot into the 

 experimental tube. 



On now admitting hydrogen at the ordinary temperature about 33 volumes were 

 immediately absorbed. When the experimental tube was warmed by a naked 

 BUNSEN flame an additional quantity of hydrogen, amounting to over 100 volumes, 

 was suddenly occluded. On heating more strongly this gas was expelled and again 

 reabsorbed on cooling. The experimental tube was now placed in a water bath. 

 When the temperature reached 88-90 C. absorption again began and continued 

 slowly at 100 C., beginning at the rate of about 1 cub. centim., or 9 volumes, per 

 minute and gradually diminishing. In an hour and a half at 100 C. about 500 

 additional volumes had been occluded, and on standing overnight at the ordinary 

 temperature only a very little, if any, hydrogen was absorbed. 



Next day an oil bath was substituted for the water bath, and the temperature was 

 gradually raised above 100 C. Absorption again went on until 130 was reached, 

 when the occluded gas began to be expelled. The temperature was therefore lowered 

 to 120. Absorption continued for two hours, and then appeared to diminish. By 

 allowing the temperature of the bath to fall to 100 absorption again took place, and 

 continued for another hour. The apparatus was now allowed to remain for 44 hours 

 at the ordinary temperature, when we were surprised to find that a further absorp- 

 tion of about 100 volumes had taken place. 



It would thus appear that after the occlusion of hydrogen has made a fair start, or 

 when the palladium has been largely converted into palladium hydrogen, a further 

 absorption is able to go on at the ordinary temperature. This may be due to the 

 change in texture of the palladium caused by ruptures between the particles of the 



