84 Professor William Arthur Bonp [FeT). 28, 



the extreme conditions of detonation the passage from to 2 maybe 

 effected in a single molecular impact. The dihydroxy derivative 

 would at once break down into carbon monoxide and hydrogen, via 

 formaldehyde. 



But when the oxygen supply is reduced below the equimolecular 

 proportion, it is evident that the initial monohydroxy derivative can- 

 not all be oxidised to the dihydroxy stage ; some of it would, there- 

 fore decompose, partly into acetylene and steam, and partly also into 

 carbon, hydrogen, and steam, together with some methane. 



In a similar manner, the combustion of ethane would involve the 

 rapid passage through ethyl alcohol to acetaldehyde and steam, with 

 subsequent decomposition of the aldehyde into carbon, hydrogen, 

 methane, and carbonic oxide, with the proviso that a reduction of 

 the oxygen supply below the equimolecular proportion, would bring 

 about in some measure the decomposition of the alcohol into ethylene 

 and steam, etc., at stage 1. 



2 

 CH3 . CH (0H)o 



OhT+^H^ I CH7rCH0'+H.,0 



\G + 2H„ + CO/ 



But the cases of ethane and ethylene are typical of all other 

 hydrocarbons, so that it may be said that, in general, the mechanism 

 of explosive combustion involves, (1) the initial formation and subse- 

 quent decomposition of hydroxylated (or " oxygenated ") molecules ; 

 (2) in a sufficient supply of oxygen, the independent oxidation of the 

 decomposition products ; (3) in an insufficient oxygen supply, the 

 subsequent breaking down of unsaturated hydrocarbons, interactions 

 between carbon and steam, or between oxides of carbon, hydrogen, 

 and steam, the final system depending on the amount of available 

 oxygen, the temperature of the flame, and the rate of cooling. 



Experiment V. — The influence of different rates of cooling of the 

 flame on the final system may be illustrated by firing an equimole- 

 cular mixture of ethane and oxygen in two glass vessels, having 

 approximately the same volume, but widely different surface areas. 

 For this purpose I have selected (1) a tube about 1 metre long and 

 2 cm. internal diameter, and (2) a globe of 8*5 cm. internal 

 diameter. Both these vessels have the same volume (about 300 c.c), 

 but the surface area of the tube is very nearly 3 times that of the 

 globe. It is therefore to be expected that, in consequence of tlie 

 more rapid cooling of the flame, there will be a greater accumulation 

 of the primary combustion products in the case of the tube experi- 

 ment. On comparing the results of the two explosions, it is at once 

 evident that more water and less carbon have been produced in the 

 case of the tube ; moreover, the pressure ratio j^a/j^j, is 1*45 as com- 



