1904.] WHARTON— PALLADIU>[ (Pd ). 335 



the processes by which pure palladium is finally attained, but 

 enough is stated to show that a complete working system is estab- 

 lished, requiring, of course, delicacy of perception and dexterous 

 manipulation, yet yielding at last a beautiful substance capable of 

 sundry uses, which are undeveloped only because no regular supply 

 could hitherto be counted on. The steady production of palladium 

 by the Orford Copper Co. is now more than 3000 ounces annually, 

 from approximately 300,000 tons of Canadian ores treated. It is 

 obvious that only as a by-product in the working of very great 

 quantities of ore can palladium be produced as here stated. 



Besides having so very high a melting point, and being at the 

 same time both hard, ductile and malleable, palladium is so 

 absolutely non-corrodible that a sheet of it may hang for a long 

 time in a laboratory exposed to chlorine and hydrogen-sulphide 

 gases without losing its polish or tarnishing. 



The wonderful occlusion or absorption of hydrogen by palladium 

 deserves special attention and invites further study. 



The volume of hydrogen thus absorbed varies greatly under 

 different circumstances, and has been variously stated by diiTerent 

 observers. According to Graham {Phil. Mag., [4] 32, 401, 503) : 



Fused palladium at 200° absorbs 68 volumes. 



Finely divided palladium at 200° *' 686 " 



Sheet palladium at ordinary temperatures (after ignition) " 376 " 



« » «< 90° to 97° " " 643 " 



.< «« 4( 245° ** " 526 « 



In Poggendorff's Annalen for 1869, Graham describes experi- 

 ments in which 900 volumes were absorbed. 



The greatest absorption observed before the experiments of 

 McElfresh (mentioned below^ was shown by electrolytically 

 precipitated palladium; the maximum being 982.14 volumes of 

 hydrogen. 



Schmidt {Ann. Physik., iv, 13,747)?/- Chem. Soc, 85, 86, 312 

 (1904), finds that the volume of hydrogen absorbed by palladium 

 increases with the fall of temperature to about 140° ; below this he 

 finds concordant results. From 140° to 300° the absorption curve 

 approaches a straight line. Absorption, and also diffusion, increases 

 with pressure as well as with temperature. 



Hoitsema (Z<?//. physikal. Chemie., 1895, 17, i),/. L. C. S., 78^ 

 11,388 (1895) examines the hypothesis of Troost and Hauteville, 

 that in the absorption of H by Pd a compound is formed repre- 



