PROFESSOR H. B. DIXO^^ OX THE RATE OF EXPLOSION IN GASES. 
123 
of carbonic oxide in abundance on the edge of the crimson zone; but I iiave left the 
further investigation of the structure of the cyanogen flame to Professor A. Smithells, 
who has devised a most ingenious method of separating the outer and inner cones of 
flame, formed when a mixture of a combustible gas and air is burnt in a Bunsen 
burner. His experiments show that the cyanogen is completely destroyed in the 
inner red flame, and carbonic oxide is the main product of its oxidation there. This 
carbonic oxide burns above, on reaching the air, with its well-known blue flame"'' 
(‘Chem. Soc. Journ.,’ 1892, vol. 1, p. 215). 
Cap. VI. —The Keactions op Carbonic Oxide in the Flame. 
If it be true that in a flame gaseous carbon burns to carbonic oxide, and that carbonic 
oxide reacts with steam (if present) to a limited extent, and is completely oxidised in 
presence of steam and oxygen, two questions arise : (1) What happens to the carbonic 
oxide first formed in the combustion of hydrocarbons or cyanogen with excess of 
oxygen ? and (2) How do these secondary reactions affect the rate of explosion ? In 
the case of cyanogen we should expect, if the gases are fairly dry, that the formation 
of carbonic acid would be comparatively slow, since no steam is formed in the reaction. 
We find, in accordance with this expectation, that so long as the mixtures will explode, 
successive additions of oxygen retard the rate more than the additions of nitrogen— 
just as in the case of electrolytic gas. This means that in the cyanogen explosion the 
excess of oxygen and carbonic oxide are as inert towards each other (as far as the 
propagation of the wave is concerned) as the excess of oxygen and steam are in the 
explosion of electrolytic gas. On the other hand, the carbonic oxide formed in the 
explosion of hydrocarbons, with excess of oxygen, meets with the steam also formed in 
the flame. This is the condition necessary for its most rapid oxidation. We should 
expect, therefore, to find in the explosions of hydrocarbons that the retarding action 
of large quantities of oxygen is partly counteracted by this secondary reaction, for the 
oxygen in presence of the steam is not inert towards the carbonic oxide. As a matter 
of fact, we find that the first additions of oxygen to the hydrocarbon mixtures retard 
more than nitrogen, but as the additions are continued the oxygen has less and less 
retarding influence compared with the nitrogen. 
When carbonic oxide, which has the same density as nitrogen, is added to 
electrolytic gas, the retarding effect on the explosion is very nearly the same as when 
an equal volume of nitrogen is added :— 
* The greenish-grey tint, observable in the outer flame, may be clue to some oxide of nitrogen formed 
in the inner flame. A little peroxide of nitrogen gives a similar tint to an ordinary Bunsen gas flame ; 
and peroxide of nitrogen is formed when cyanogen is burnt under certain conditions {vide ‘ Chem. Soc*. 
Journ.,’ 1886, vol. 1, p. 390). 
R 
