DIALTTIC SEPARATION OF GASES BY COLLOID SEPTA. 



421 



Absorption and detention of Hydrogen by Platinum. — The passage of a gas through a 

 colloid septum is preceded by the condensation of the gas in the substance of the septum, 

 according to the views taken in this paper. Is a plate of ignited platinum capable, then, 

 of condensing and liquefying hydrogen gas^ The subject could scarcely admit of expe- 

 rimental investigation without the application of the same useful air-exhauster that was 

 employed with the non-metallic colloids. The metal was always treated in the same 

 manner; so that a description of the details of one experiment will apply to all*. 



Platinum wire or plate being provided, the surface of the metal was first divested of 

 all adhering oily matter, by boiling in caustic alkali and afterwards in distilled water. 



The platinum, generally in the form of wire, was then introduced into a porcelain 

 tube M, N (fig. 2), glazed both outside and inside, 0-55 metre in length and 23 millims. 



Pis. 2. 



in internal diameter. This tube could be heated either by means of the combustion- 

 furnace used for organic analysis, or by placing the tube across the chamber of a small 



* Platinum in the peculiar condition of platinum-black absorbs 745 times its volume of hydrogen gas. — Traite 

 de Chimie Generale, par MM. Peiouze et FaiMr, t. iii. p. 398. 



