Dr . Henry on the action of finely divided platinum on 
IX. Mixtures of Hydrogen , Carbonic Oxide , Carburetted 
Hydrogen , and Olefiant Gases with Oxygen. 
In mixtures of these four gases with oxygen, it was found, 
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 es- 
caped combustion, unless the hydrogen were in such propor- 
tion 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 dis- 
posed 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 gene- 
rally 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 en- 
tirely acidified, and the whole of the carburetted hydrogen be 
left unaltered. This will generally be found to have been 
