IN GASES: HYDROGEN, CARBONIC OXIDE, AND OXYGEN. 641 
tube is found coated with a very fine layer of carbon. Whether under these con¬ 
ditions steam is necessary for the propagation of the explosive wave is doubtful, 
it is possible that the initial reaction between the carbonic oxide, steam, and 
oxygen increasing in velocity as the flame travels down the tube, produces at last 
a temperature at which a new reaction is determined. But such conditions do 
not occur in the partial burning of the comparatively short columns of gases that 
have been employed in researches on the incomplete combustion of gases. 
The result of these various experiments may be thus summarised :— 
1. The drier the mixture of carbonic oxide and oxygen, the greater the pressure 
it can withstand without igniting when a spark is passed through it. 
2. The addition of a trace of aqueous vapour to the non-inflammable mixture 
causes it to become inflammable, all other conditions remaining the same. 
3. The addition of a ti’ace of hydrogen or of a volatile body containing hydrogen 
causes the dry mixture to become inflammable, all other conditions remaining the 
same. 
4. The rapidity of explosion of the mixture in a tube one metre long is greater 
with a large quantity of aqueous vapour than when only a trace is present. 
These well-established facts, coupled with the fact that carbonic oxide does de¬ 
compose steam at a high temperature, appear to me to show conclusively that in 
the ordinary explosion of carbonic oxide and oxygen, the union is not a direct one, 
but is effected indirectly by the agency of hydrogen. 
In a paper on the alkaline peroxides,* the late Sir B. Brodje has thus described 
such an indirect action :—“ The alkaline peroxides have a double function, and can 
be used as agents either of oxidation or of reduction. By certain modifications 
of the conditions of the experiment, we can produce separately either result. It is 
not unreasonable to suppose that, among the numerous and varied forms of chemical 
decomposition, instances would be found in which these phenomena would occur 
simultaneously. If this were to be the case the result would be what is termed 
a contact or catalytic decomposition, but caused by two successive changes of a 
normal chemical character.” 
The action of steam in determining the union of oxygen with carbonic oxide is of 
this kind ; that is to say, when carbonic oxide and oxygen are exploded in a eudio¬ 
meter, the heat of the spark causes the carbonic oxide in its immediate neighbourhood 
to decompose the steam usually present, and the hydrogen, liberated by this reaction, 
unites with the oxygen to re-form steam. The steam so formed reacts with more 
carbonic oxide, and so the alternate changes go on until all the carbonic oxide is 
oxidized according to the two equations 
CO + ICO = C0 2 + 2 H 
2Ho+ Oo = 2H,0. 
MDCCCLXX XIV. 
* Phil. Trans., 1860. 
4 N 
