[ 105 ] 



III. On the Occlusion of Hydrogen and Oxyrjen by Palladium. 



By LUDWIU MOND, Ph.D., F.R.S., WILLIAM KAMSAY, Ph.D., F.R.S., and 



JOHN SHIELDS, D.Sc., Ph.D. 



Received December 8, Read December 10, 1897. 



CONTENTS. 



PAGE 



I. Introduction 105 



II. Preparation of the Palladium 100 



III. Density of Palladium 107 



IV. Analysis of Palladium Black 107 



V. Absorption of Oxygen by Palladium 108 



VI. Observations on the Occlusion of Hydrogen by Palladium Black, Sponge, and Foil 111 



VII. The Heat of Occlusion of Hydrogen by Palladium Black 117 



VIII. Investigation of the Ratio Palladium : Hydrogen J 20 



IX. On the Heat of Occlusion and the Heat of Condensation 122 



X. The Influence of Increased Pressure on the Occlusion of Hydrogen by Palladium 



Black 12:! 



XI. The Heat of Absorption of Oxygen by Palladium Black 121 



I. Introduction. 



SINCE the discovery by GRAHAM ('Phil. Trans.,' I860, p. 399, also ' GRAHAM'S 

 Researches,' p. 235), that palladium possesses the property of occluding or absorbing 

 large quantities of hydrogen, chemical literature has been enriched by various con- 

 tributions to our knowledge of this interesting phenomenon. To mention only a few 

 of these, some of which will later on be considered in detail, we have the results of 

 investigations on the change of volume undergone by palladium on the occlusion of 

 hydrogen, the density of the occluded hydrogen, the heat changes which take place, 

 and the pressure of " palladium hydrogen " at different temperatures, &c. 



The solution of hydrogen in, or the combination of hydrogen with, palladium, 

 which we may be permitted provisionally to term palladium hydrogen, is now often 

 used in laboratories as a convenient source of pure hydrogen ; and finely divided 

 palladium, on account of the facility with which it absorbs hydrogen, is also 

 extensively employed in gas analysis. Hydrogen, occluded by palladium, may con- 

 veniently be weighed as palladium hydrogen, and recourse was had by REISER 



VOL. CXCI. A. P 12.5.98 





