PROFESSOR H. B. DIXON OX THE RATE OF EXPLOSION IN GASES. 143 
of the wave the cooling due to expansion is so rapid that some molecules of hydrogen 
and oxygen, which are unburnt in the wave-front, have not time to combine before 
they are cooled below the temperature of combination. In a leaden tube, 9 mm. in 
diameter and lOB metres long, about 1 per cent, of electrolytic gas was found 
uncombined after the explosion. That this incompleteness of combustion v\ms not due 
to the cooling effect of the walls was shown by making comparative experiments in 
tubes 4 mm. and 19 mm. in diameter. Nearly the same percentage of unburnt 
residue was found in all the tubes, and also when the gases were detonated in an iron 
bomb 100 mm. in diameter. We have, therefore, positive evidence that in the 
explosion-wave the combustion of electrolytic gas is incomplete; it seems, therefore, 
not unreasonable to assume that in the wave-front— i.e., at the highest temperature— 
a considerable proportion of hydrogen and oxygen is uncombined, and the propagation 
of the wave is retarded accordingly. 
The residual gases, left after the explosion of electrolytic gas, were examined for 
peroxide of hydrogen; the water condensed on the tube was also washed out and 
examined. In neither case could peroxide of hydrogen be detected. If the view were 
correct that hydrogen and oxygen first form peroxide on explosion, it would seem 
likely that, in the rapid cooling, some of the peroxide would remain undecomposed, 
and be found in the residue. 
In the explosion of carbonic oxide and oxygen a similar residue of unburnt gas is 
found—indicating the dissociation of carbonic acid at the temperature of the wave. 
No trace of peroxide of hydrogen could be detected in the tube. These observations 
give no support to the view put forward by Moritz Traube that steam promotes 
the oxidation of carbonic oxide by dividing with it the molecules of oxygen :— 
CO -f 00 + OH3 CO2 + O2H3 
and that the peroxide so formed is again reduced to steam by more carbonic oxide:— 
CO + O3H2 = CO3 -f OH3. 
Cap. IX.— The Explosion of Hydrogen and Chlorine. 
The coincidences and the divergences found between the calculated and observed 
rates of explosion, as described above, made it important to examine a reaction in 
which no steam should be formed, and, if possible, one in which no alteration in 
volume should be produced. The simplest case fulfilling these conditions is the 
explosion of hydrogen and chlorine; a reaction which has the further advantage of 
forming, as the product of explosion, a gas which approximates to a perfect gas. So 
* ‘ Bcr. Dent. Cliem. Ges.,’ vol. 18, p. 1890. (See ‘Chem. Soc. Journ.,’ 1886, vol. 1, p. 94.) 
