1825.] finely divided Platinnm on Gaseous Mixtures. 417 



ture of the atmosphere, by means of the sponge ; but though 

 this is in strictness true, yet the combination, in all the experi- 

 ments J have made, has been extremely slow, and the due dimi- 

 nution of volume has not been completed till several days have 

 elapsed. On mixtures of olefiant gas, of carburetted hydrogen, 

 or of cyanogen, with oxygen, the sponge does not, by any dura- 

 tion of contact, exert the smallest action at common tempera- 

 tures. 



It was this inefficiency of the platinum sponge on the com- 

 pounds of charcoal and hydrogen in mixture with oxygen, while 

 it acts so remarkably on common hydrogen, and also, though 

 slowly, on carbonic oxide, that suggested to me the possibility 

 of solving, by its means, some interesting problems in gaseous 

 analysis. I hoped, more especially, to be able to separate from 

 each other the gases constituting certain mixtures, to the com- 

 position of which approximations only had been hitherto made, 

 by comparing the phsenomena and results of their combustion 

 with those which ought to ensue, supposing such mixtures to 

 consist of certain hypothetical proportions of known gases. It 

 might, for instance, be expected, that from a mixture of hydro- 

 gen and carburetted hydrogen with oxygen, the platinum sponge 

 would cause the removal of the hydrogen, leaving the carbu- 

 retted hydrogen unaltered. To ascertain this, and a variety of 

 similar facts, I made artificial mixtures of the combustible gases 

 in known volumes ; and submitted them, mixed with oxygen, 

 sometimes to contact with the sponge, and sometimes with the 

 balls made of clay and platinum, described by Professor Dobe- 

 reiner.* 



Sect. I. — On the Action of finely divided Platinum on Gaseous 

 Mixtures at common Temperatures. 



1. Mixtures of Hydrogen and Olefiant Gases with Oxygen. 



When to equal volumes of olefiant gas, and an explosive 

 mixture (which is to be understood, whenever it is so named, 

 as consisting of two volumes of hydrogen and one of oxygen 

 gases), one of the platinum balls, recently heated by the blow- 

 pipe, and allowed to cool during eight or ten seconds, is intro- 

 duced through mercury, a rapid diminution of volume takes 

 place 'y the whole of the hydrogen and oxygen gases is con- 

 densed ; but the olefiant gas is either not at all, or very little 



* The proportions which I used, but which perhaps are not of much importance,' 

 were.two parts of fine china clay, and three parts of spongy platinum mixed with water 

 into a paste, wliich was moulded into small spherules, about the size of j)eas. The 

 sponge, best adapted to the purpose of acting on mixed gases, is obtained by using a 

 little pressure to the ammonia-muriate, after putting it into the crucible. If too light 

 and porous, tlie sponge is apt to absorb mercury by being repeatedly pa,sscd through it, 

 and to become amalgamated. In order that the balls or sponge might be removed after 

 their full action, they were fastened to pieces of platinum wii'c. 



Neio Series J vol. ix. 2 E 



