428 MR. T. GEAIIAM ON THE ABSORPTION AND 



barora. The whole gas extricated (68 vols.) seems unusually small, but it corresponds 

 closely enough with the volume calculated from the increase of the palladium in weight. 

 An inferior absorbing ])ower for hydrogen appears to be connected in both platinum 

 and palladium with the fusion of the metal. 



6. A portion of similar palladium-foil, charged with hydrogen, was found to have its 

 gas reduced from 20-7 to 16"2 cub. centims. after exposure to the air for forty-two 

 hours. The liquid hydrogen, whether held by the substance or in the pores of the 

 metal, appears therefore to evaporate slowly at the temperature of the atmosphere, 

 therm. 19°, barom. 752 millims. 



7. Spongy palladium, from the ignition of the cyanide, being heated in hydrogen at 

 200°, and allowed to cool slowly in the same gas for four hours, the metal was found to 

 have taken up 686 vols, of hydrogen. 



Treated in a similar manner with air, spongy palladium exhibited no absorbing-power 

 for oxygen or nitrogen. 



Hydrogen, condensed either in the palladium sponge or foil, was observed to have its 

 chemical affinities enhanced. The palladium being placed in dilute solutions of the 

 following substances for twenty-four hours in the dark at the ordinary temperature, the 

 action of the hydrogen became manifest. 



Persalt of iron became protosalt. 



Ferricyanide of potassium became ferrocyanide. 



Chlorine-water became hydrochloric acid. 



Iodine-water became hydriodic acid*. 



Apart from hydrogen, the palladium sponge exhibits a power of selection and absorp- 

 tion of alcohol in preference to water. 30 grms. of the sponge were left in contact with 

 9-5 cub. centims. of dilute alcohol of specific gravity 0-893, for fifty-one hours, sealed in a 

 tube. The supernatant liquid now drawn off to the extent of 3-9 cub. centims. was of 

 specific gravity 0-901, while the portion retained by the palladium was found when 

 distilled to be of specific gravity 0-885, or it was sensibly concentrated. This chemical 

 action of palladium sponge was more than once verified. Platinum sponge, on the other 

 hand, exhibited no indication of a similar separating-power ; nor did the sponge of iron 

 reduced by hydrogen from the oxide. 



8. Connected, it may be, with this chemico-molecular action of palladium is the variable 

 absorptive power for different liquids exhibited by palladium-foil. Immersed in various 

 liquids for an hour, and afterwards dried by pressure for a few seconds between folds of 

 blotting-paper, a quantity of palladium-foil represented by 1000 was found to retain in 

 its pores — 



Of Water 1-18 part. 



Of Alcohol (0-802) 5-5 parts. 



* The power of platinum-black charged -with hydrogen to communicate the latter element to organic com- 

 pounds has lately been observed by M. P. de Wilde, following Dr. Debits. — Bulletin de la Society Chimiqne, 

 Mars 1866. 



