GASEOUS COMBUSTION AT HIGH PRESSURES. 



311 



down into carbon, hydrogen, methane and carbon monoxide, in accordance with the 

 scheme. 



H 



H.C.H 



H.C.H 



H 



"(1) CH 4 +CO 

 (2) C + 2H. + CO 



4H.O 





H.O + ILC.CHO 



This conclusion was endorsed, in general terms, by Prof. H. B. DIXON in his 

 Presidential Address to the Chemical Society in 1910, as the result of his own 

 independent observations on the rate of detonation of a mixture C 2 H 6 + 2 .* 



The modes of decomposition of dihydroxyethane and acetaldehyde at high tempera- 

 tures, and the nature of the resulting products are such as would permit of the play of 

 several secondary interactions, such for instance as (i.) CO + OH 2 ^__1C0 2 + H,, and 

 (ii.) C + OH 2 = CO + H 2 , during the cooling period of an explosion. And therefore it 

 is to be expected that the final result in any particular case will depend upon (i.) the 

 maximum flame temperature and the rate of the subsequent cooling therefrom, which 

 conditions are in turn governed by such factors as initial pressure, and (ii.) the phase 

 attained by the explosion (i.e., " inflammation" or " detonation"), and (iii.) the area 

 and nature of the cooling surface per unit volume presented by the walls of the 

 containing vessel. 



The dependence of the final result upon such conditions is well illustrated by the 

 following tabulated records (Table XV.) of the behaviour of a mixture C 2 H 6 + O a (i.) 

 when inflamed at less than atmospheric pressure in glass vessels presenting very 

 different areas of cooling surfaces to a given volume of the combining gases, and (ii.) 

 when detonated in a leaden coil at initial pressures of 900 to 1200 mm. 



It is thus seen (l) that the rapid cooling of the exploded gases in (a) favoured the 

 survival of steam, aldehydes, and unsaturated hydrocarbons ; (2) that the longer 

 duration of the flame in (b) greatly increased the separation of carbon, at the expense 

 of the saturated hydrocarbons and aldehyde, whilst it also favoured the secondary 

 reduction of steam by carbon ; and (3) that the much higher temperatures and 

 pressures attained in detonation, whilst militating against the survival of aldehyde 

 and unsaturated hydrocarbons, was chiefly effective in promoting the secondary 

 reduction of steam by carbon. Nevertheless, even in detonation, as much as 17 to 20 

 per cent, of the original oxygen appeared as steam in the final products. 



The foregoing considerations led us to study in detail the behaviour of the same 

 mixture when exploded in bomb A, under various initial pressures between 10 and 40 



* ' Trans. Chem. Soc.' 1910, vol. 97, p. 665. 



