bi) Means of Dcebereiner's Eudiometer. 275 



by varying the proportion of hydrogen, that hydrogen and 

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

 and carburetted hydrogen with the greatest difficulty. When 

 the action of the sponge was moderate, only the hydrogen 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 com- 

 bustion, 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 

 facility ; 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 con- 

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

 olefiant gas is absent, so to regulate the proportion of hydro- 

 gen, 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 ni- 

 trous gas when the former is admitted to the latter in a nar- 

 row tube. 



Section 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 be- 

 ing explained, by examining the facts that have been stated, 

 in connexion with the degrees of combustibility of the com- 

 pound gases under ordinary circumstances. The precise de- 

 gree 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 with- 



M m 2 out 



