422 Dr. Henri/ on the Action of [June, 



carbonic oxide are most easily acted upon ; then olefiant gas ; 

 and carburetted hydrogen with the greatest difficulty. When 

 the action of the sponge was moderately intense, only the hydro- 

 gen and carbonic oxide were consumed, or at most the olefiant 

 gas was but partially acted upon. Adding more hydrogen, so 

 as to occasion a more rapid diminution, the olefiant gas also was 

 burned ; but the carburetted hydrogen always escaped combus- 

 tion, unless the hydrogen were in such proportion that the ball 

 or sponge became red hot. 



From the facts which have been stated, it appears that when 

 the compound combustible gases mixed with each other, with 

 hydrogen, and with oxygen, are exposed to the platinum balls 

 or sponge, the several gases are not acted upon with equal faci- 

 lity ; but that carbonic oxide is most disposed to unite with 

 oxygen; then olefiant gas; and lastly, carburetted hydrogen. 

 By due regulation of the proportion of hydrogen, it is possible 

 to change the whole of the carbonic oxide into carbonic acid, 

 without acting on the olefiant gas or carburetted hydrogen. 

 With respect indeed to olefiant gas, this exclusion is attended 

 with some difficulty, and it is generally more or less converted 

 into carbonic acid and water. But it is easy, when olefiant gas 

 is absent, so to regulate the proportion of hydrogen, that the 

 carbonic oxide may be entirely acidified, and the whole of the 

 carburetted hydrogen be left unaltered. This will generally be 

 found to have been accomplished, when the platinum ball has 

 occasioned a diminution of the mixture, at about the same rate 

 as atmospheric air is diminished by nitrous gas, when the former 

 is admitted to the latter in a narrow tube. 



Sect. II, — On the Effect of finely divided Platinum on Gaseous 

 Mixtures at increased Temperatures. 



The effect of varying the proportion of free hydrogen to the 

 compound combustible gases, on the degree of action which is 

 excited by the platinum sponge, will perhaps admit of being 

 explanied, by examining the facts that have been stated, in con- 

 nexion with the degrees of combustibility of the compound 

 gases under ordinary circumstances. The precise degree of 

 temperature at which any one of them burns is not known, on 

 account of the imperfection of our present methods of measuring 

 high degrees of heat. It has been ascertained, however, by Sir 

 Humphry Davy,* that at a heat between that of boiling mercury, 

 and that which renders glass luminous in the dark, hydrogen 

 and oxygen gases unite silently, and without any light benig 

 evolved ; that carbonic oxide is as inflammable as hydrogen ; 

 that olefiant gas is fired by iron and charcoal heated to redness ; 



♦ OnFlame,8vo. p. 72. 



