Intelligence and Miscellaneous Articles. 



399 



stant (which is the character of a combination) as soon as there are 

 not more than GOO volumes of the gas — a quantity which corre- 

 sponds ro -£ equivalent of hydrogen for 1 equivalent of palladium. 

 Prom this moment the hydrogenized palladium behaves as a definite 

 combination, susceptible of dissociation, and of which the tension 

 does not depend on the temperature — after the manner of carbonate 

 of lime, studied by M. Debray. 



In order to exhibit more distinctly this invariability of pressure 

 which is characteristic of combination, we will cite the results of an 

 experiment made at the temperatures in the vicinity of 160°. 





Volumes of hydro- 



1 Tensions of the 



Temperatures. 



gen gas fixed in 

 the palladium. 



definite compound. 







millim. 



160 



589 



14/5 



161 



574 



1500 



160-5 



480 



1480 



161 



290 



1482 



160 



200* 



1480 



Series of observations made between 20° and 180° have taught 

 us that within these limits of temperature the phenomenon retains 

 the same characters ; that is to say, the tension remains constant 

 as soon as the quantity of fixed hydrogen is no more than 600 vo- 

 lumes, which corresponds to the formula Pa 2 H. We have thus 

 obtained the following numbers, which permit us to construct the 

 curve of the dissociation tensions of the compound : — 



* We have therefore been able, in the experiment cited, to take away 

 two thirds of the gas without diminishing the tension. When the last 

 traces of Pa 2 H have been decomposed, the palladium remains saturated 

 with dissolved hydrogen gas. We then reenter the conditions of a pheno- 

 menon of solution; and fresh subtractions of gas should bring a rapid 

 decrease of the pressure : this is evidenced by the three following determi- 

 nations : — 



Temperatures. 



Volumes of gas. 



Tensions. 



o 

 161 

 160 

 161 



62 

 38 

 29 



millira. 

 731 

 435 

 391 



