836 WfTARTON — PALLADIUM (Pd). [April 7, 



sented by PdzH, but he does not agree with those authors. Debray 

 thought the compound Pd^H.^ was formed. Why should a chemical 

 formula be sought for the compound of palladium and hydrogen 

 since they combine together in practically all proportions, thus 

 indicating it to be a simple alloy ? 



McElfresh i^Pi'oc. Am. Acad. Arts and Sciences, vol. xxxix, No. 

 14, Jan., 1904), examining critically the influence of occluded 

 hydrogen upon the electrical resistance of palladium, finds that 

 resistance to increase constantly, but not at a uniform rate, as the 

 occluded hydrogen increases; the maximum increase of the resist- 

 ance being 68 per cent, when 1030 volumes were occluded. This 

 absorption, reached by continuous exposure for 30 hours, is the 

 highest yet observed and probably indicates complete saturation. 



McElfresh considered Knott's method {^Pi'oc. Roy. Soc. Edtn., 

 vol. xii, 1882, 1883) of determining the amount of occlusion, by 

 measuring the increase in weight of the palladium treated, to be 

 incapable of accuracy ; he was also dissatisfied with the results 

 obtained with imperfect apparatus by supplying to palladium a 

 measured quantity of electrolytically produced hydrogen and 

 deducting therefrom the quantity remaining after various periods 

 of absorption. He therefore avoided the error inherent in such 

 apparatus by using in this latter method ingenious apparatus of his 

 own devising, thus reaching conclusions which appear quite reliable. 



It is remarkable that Richter's Chemis/?y, as translated by Edgar 

 F. Smith, states (p. 46) that the conductivity of palladium for both 

 heat and electricity is little affected by its occlusion of hydrogen. 



As for the discharge of occluded hydrogen from palladium, 

 Graham states that ''the gas exhibits no disposition to leave the 

 metal and escape into a vacuum at the temperature of its absorp- 

 tion." Edgar F. Smith informs me that he finds charged palla- 

 dium immersed in water at 160° to give off hydrogen with freedom 

 comparable to the escape of carbonic acid from soda water. 



Baskerville informs me that, in examining palladium for radio- 

 activity, he found none in either of the two forms I sent him at 

 his request for that purpose — namely, electrolytically deposited 

 scale such as mentioned above in this paper, and similar scale which 

 had been fused into a large button. But when he examined the 

 same specimens after charging them in a finely divided state with 

 hydrogen, he found slight indications of radio-activity in the first, 

 but none in the second. He therefore asks whether, during the 

 electro-deposition, a tension might have accumulated which 



