510 Mr. T. Graham on the Absorption and 



nel, by the help of which another analogous body like nitrogen 

 might be conceived capable of passing through the platinum in 

 small quantity, by a process of liquid or gaseous diffusion. 



Absorption and detention of Hydrogen by Platinum. — The pass- 

 age of a gas through a colloid septum is preceded by the con- 

 densation 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 experimental investigation without 

 the application of the same useful air-exhauster that was em- 

 ployed 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 intro- 

 duced into a porcelain tube M, N (fig. 2), glazed both outside 

 and inside, 0*55 metre in length and 23 millims. 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 cylindrical furnace. The 

 porcelain tube was fitted at both ends with perforated corks, well 

 cemented with fused gutta perch a, and provided each with a 

 small quill tube. Such may be described as the distillatory ap- 

 paratus employed. It was connected at the end N with the 

 Sprengel pump A B, to be used as an exhauster and transferrer of 

 gas, by means of good caoutchouc adapters (not vulcanized), and 

 at the other end, M, with the apparatus for supplying dry hy- 

 drogen, atmospheric air, or any other gas. By a screw clamp 

 upon the adapter at M, the tube could be closed, and the gas- 

 producing apparatus then detached, leaving the porcelain tube 

 shut at one end. A tube of the hard glass used in combustion 

 analysis may be substituted for the porcelain tube in many such 

 experiments. A less degree of heat suffices than was at first 

 supposed. 



The porcelain tube is exhausted by continuing the action of 

 the Sprengel for ten or fifteen minutes, till small bubbles of gas 

 cease to be delivered by the tube A B in the mercurial trough 

 below. The sufficiency of the joints is thus first ascertained. 

 Heat being then applied to the porcelain tube, its impermeability 

 at a red heat will also be tested. 



The platinum, when introduced, was confined to about two- 



* Platinum in the peculiar condition of platinum-black absorbs 745 times 

 its volume of hydrogen gas. — Traite de Chimie Generate, par MM. Pelouze 

 et Fremy, vol. iii. p. 398. 



