G8 Royal Institution : — Dr. W. Odling on some Effects 



The quantity of hydrogen held by the metal at these high tem- 

 peratures may become too small to be appreciated; but I presume 

 it is still present, and travels through the metal by a kind of rapid 

 cementation. This extreme mobility is a singular property of hy- 

 drogen, which was involved in the fundamental discovery, by MM. 

 H. Sainte-Claire Deville and Troost, of the passage of that gas through 

 plates of iron and platinum at high temperatures. 



The marked rapidity of the passage of the same gas through 

 a thin sheet of caoutchouc appears to be more capable of explana- 

 tion on known principles. Caoutchouc of less than 0*1 millimetre in 

 thickness, if impregnated with hydrogen, loses its gas entirely by 

 the most momentary exposure to the air. A tube of 2 millimetres in 

 thickness, through which hydrogen and carbonic acid were singly 

 passed, each for an hour, was found to retain — 



Of hydrogen 0*01 13 volume. 



Of carbonic acid 0*2200 „ 



The absorption, then, is in the proportion of 1 hydrogen to 20 car- 

 bonic acid, but the comparative rate of penetration of the two gases 

 through a sheet of caoutchouc is as 1 hydrogen to 2\ carbonic acid ; 

 or the hydrogen moves eight times as rapidly as the density of its 

 solution would indicate. But these gases differ in diffusibility as 

 carbonic acid 1 to hydrogen 4 '7. The rapid passage of hydrogen 

 through caoutchouc is thus partly explained by the rapid manner in 

 which that gas is brought to one surface of the sheet and conveyed 

 away from the other by gaseous diffusion. Again, both substances 

 travel through the substance of the caoutchouc by their diffusibility 

 as liquids. Suppose hydrogen in that form to be nearly as much 

 more diffusive than the other substance as it is when both are gaseous, 

 then the observed rapid passage of hydrogen through caoutchouc 

 would appear to be fully accounted for. 



Liquid diffusion has also a bearing upon the rapid dissemination 

 of hydrogen through a soft colloid metal, like palladium or plati- 

 num, at a high temperature. The liquid diffusion of salts in water 

 is known to be six times as rapid at 100° as at 0°. If the diffusion 

 of liquid hydrogen increases with temperature in an equal ratio, it 

 must become a very rapid movement at a red heat. Although the 

 quantity absorbed may be reduced (or the channel narrowed), the 

 flow of liquid may thus be increased in velocity. The whole phe- 

 nomena appear to be consistent with the solution of liquid hydrogen 

 in the colloid metal. The " solution affinity " of metals appears to 

 be nearly confined to hydrogen and carbonic oxide, so that metals 

 are not sensibly penetrated by other gases than these. 



ROYAL INSTITUTION OF GREAT BRITAIN. 



May 22, 1868.— "On some Effects of the Heat of the Oxyhy- 

 drogen Flame." By William Odling, M.B., F.R.S. 



I. 



Chemical changes, whether of combination or decomposition, 

 result in the production of new bodies which, under the conditions 



