398 



Intelligence and Miscellaneous Articles* 



which have dissolved gases (such as water charged with carbonic 

 acid), and those which have condensed it (such as platinum-black 

 charged with hydrogen), emit gases which, for one and the same 

 temperature, have tensions variable with the state of saturation of 

 the material. It is b}^ the study of the tensions that we have arrived 

 at the recognition of the simultaneous production of a definite 

 compound and of a solution of hydrogen gas. 



The palladium, saturated with hydrogen at the negative pole of 

 a voltameter, was introduced into a glass tube communicating at 

 one extremity with a manometer, and at the other with a Sprengel 

 pump, which permitted a vacuum to be produced at the commence- 

 ment, and afterwards, in the course of the experiment, determined 

 volumes of gas to be expelled*. 



If the operation take place at about 100°, successively increasing 

 quantities of gas being taken away, we obtain, with either cast or 

 spongy palladium, the results inscribed in the following Table, which 

 contains the observed pressures for different degrees of saturation. 



Temperatures. 



Cast palladium. 



Spongy palladium. 



Volumes of hy- 

 drogen fixed in 

 the palladium. 



Tensions. 



Volumes of hy- 

 drogen fixed in 

 the palladium. 



Tensions. 



100°-2 

 99-8 

 100 

 100 

 100-5 



809 

 743 

 700 

 672 

 642 



dib 



595 

 402 



millim. 

 1428 

 909 

 598 

 454 

 353 



"238 

 225 

 230 



775 

 743 

 718 



684 



millim. 

 715 

 493 

 361 

 247 

 » 



99-8 

 100 

 1001 



608 

 590 

 300 



227 

 225 

 224 



The Table shows us : — (1) that as long as the volume of hydrogen 

 fixed is more than 600 times the volume of the palladium, the pres- 

 sure decreases very rapidly at each subtraction of hydrogen, which 

 is the character of a solution ; (2) that the pressure becomes con- 



* As palladium saturated with gas disengages hydrogen at the ordinary 

 temperature, it is necessary, if we wish to know exactly the total volume 

 of gas absorbed, to put the metal, on taking it out of the voltameter, into 

 a small balloon full of boiling water and furnished with a discharge-tube. 

 The temperature of the balloon is raised to the boiling-point of water, and 

 the gas discharged is collected. After cooling, the metal can be handled 

 in order to introduce it into the manometric apparatus without fear of 

 losing any gas. This preliminary operation is indispensable when the 

 forged metal is operated on, which, when withdrawn from the voltameter, 

 grows rapidly hot in contact with the air, in consequence of the combustion 

 of the hydrogen. 



