400 



Intelligence and Miscellaneous Articles. 



Temperatures. 



Dissociation ten- 

 sions of Pa 2 H. 



Temperatures. 



Dissociation ten- 

 sions of Pa 2 H. ! 



i 



1 



millim. 





millim. 



20 



10 



100 



232 



30 



16 



110 



336 



40 



25 



120 



467 



50 



36 



130 



624 



60 



50 



140 



812 



70 



65 



150 



1104 



80 



106 



160 



1475 



90 



160 



170 



i 



1840 



Remarks. — The numbers in this Table were obtained with a palladium 

 wire ; this was preferred to a sheet for these determinations, because the 

 boundary tension is more rapidly reached. Besides, a sheet leads, although 

 more slowly, to the same results. The cast and the forged metal present 

 no difference in respect of the tensions ; and the behaviour is the same, 

 whether the metal has been charged by the pile or by a prolonged stay in 

 hydrogen. 



The above numbers show that Pa 2 H does not sensibly emit gas 

 at the ordinary temperature. The hydrogen-tensions which limit 

 the decomposition of the compound increase at first slowly; but 

 from 140° very small additions to the temperature are attended by 

 a rapid augmentation of the pressure. Between 130° and 140° 

 the tension becomes equal to the pressure of the atmosphere. 



This compound, then, cannot be prepared at a higher temperature 

 than 130°, unless the hydrogen be compressed. The most conve- 

 nient temperature for its production is that of boiling water, at 

 which the dissociation tension is below one third of the atmospheric 

 pressure. 



In brief, our experiments prove that palladium forms with hy- 

 drogen a definite compound, of which the formula is Pa 2 H. This 

 combination, once formed, can dissolve hydrogen gas after the 

 manner of platinum, and in quantity variable with its physical 

 state. This property of Pa 2 H explains the difference between the 

 numerical results obtained by Graham according as he employed 

 palladium wire or spongy palladium. 



In another communication we will show that potassium and 

 sodium form combinations with hydrogen which have the formulae 

 .K 2 H, Na 2 H (K==39, Na=23). These, together with hydrogenized 

 palladium, form a series parallel to that of which M. Wurtz dis- 

 covered the first term in the combination of copper with Ivy drogen 

 Cu 2 H 2 (Cu=63*5), and to which he gave the name of hydride 

 of copper. — Coniptes Benclus de VAcad. des Sciences, vol. lxxviii. 

 pp. 686-690. 



