1908] on Explosive Oombustmi. 77 



problem might not lie in the assumption of an initial association of 

 the hydrocarbon and oxygen forming an unstable "oxygenated" 

 molecule, which subsequently rapidly decomposes. Thus, for example, 

 the changes involved in the explosive combustion of an equimolecular 

 mixture of ethylene and oxygen might conceivably be represented 

 somewhat as foUow^s : — 



C2H4 + Oo = [C2H4O2] = 2C0 + 2H2 

 unstable 



Many years ago, indeed. Professor H. E, Armstrong, suggested 

 that the combustion of a hydrocarbon takes place under the conjoint 

 influence of water and oxygen, and involves the successive formation 

 of intermediate ^^ hydroxi/latecV' molecules, which at high tempera- 

 tures rapidly decompose into simpler products. Little notice was 

 taken of his suggestion at the time, but recent researches have shown 

 that " hydroxylated " molecules are probably formed, even in flames, 

 although I think it doubtful whether water vapour is an essential 

 factor in the process. 



The researches recently carried out at the Manchester University, 

 have covered the entire range of conditions under which hydro- 

 carbons can be burned, from the slow flameless combustion dis- 

 covered by Davy, right up to the extreme conditions of detonation. 

 An exhaustive study of the slow combustion of methane, ethane, 

 ethylene, and acetylene, at temperatures between 250° and 400° C, 

 afforded decisive evidence against the preferential burning, whether 

 of carbon or of hydrogen. Large quantities of aldehydic intermediate 

 products were isolated, and the balance of evidence was decidedly in 

 favour of the " liydroxylatioa " theory, with the proviso, however, 

 that the oxygen is directly active. Finally, the following scheme 

 was put forward for the slow combustion of ethane, and ethylene at 

 250° to 850^ C. 



CH:i.CH3 -> CH3.CH.2OH -> CH3.CH(0H)2 -^ CO +_H20 + H.CHO -> H.COOH -^ C0(0H)2 



. — -^ ForTnaldehyde Formic Carbonic 



Ethane Ethyl Alcohol HoO + CH3.CHO— i Acid Acid 



I Acttaldthyde . ' , — — ■ ^ 



CO + H2O CO2 + H2O. 



CHgrCHg. ^H2C:CH(0H) ->- (HO)CH:CH(OH) ^ H.COOH ^ C0(0H)2 



,— — ' — -^ Formic Acid Carbonic Acid 



Ethylene 2 H.CHO , ■ — -, , ' 



Formaldehyde ' CO + H2O COo + H2O 



Translated into words, this means that, in the case of ethane, the 

 initial oxidation product is probably ethyl alcohol C2H5.OH. The 

 alcohol has not, indeed, been actually isolated during the slow com- 

 bustion at 300^ 0., chiefly because it is much more rapidly oxidised 



