1908] Explosive Combustioii. 



WEEKLY EVENING MEETING 



Friday, February 2<s, 19()S. 



George Matthey, EtsQ., F.R.8., in the Chair 



Professor Williajvi Arthur Boxe, D.Sc. Ph.D. F.R.S. 



Explosive Gomhustion, with iSpecial Reference to that of 

 Hydrocai'bons. 



It is hardly necessary to remind you that the subject of my discourse 

 will be ever associated with the illustrious name of Davy. Davy 

 turned his attention to the phenomena of flame in the year 1815, in 

 response to an urgent appeal on the part of a committee formed in 

 the North of England, to investigate the causes of accidents arising 

 from the explosion of fire-damp in coal mines, and to devise means 

 for their prevention. The perennial interest of his researches, how- 

 ever, lies not so much in their immediate practical success, great as 

 this undoubtedly was, as in the broader theoretical issues which were 

 disclosed, and brought within the region of experimental enquiry, 

 by so splendid an exercise of genius. 



Davy insisted on the necessity of considering flames in all cases 

 " As the combustion of an explosive mixture of inflammable gas, or 

 vapour, and air," and he defined flame as "aeriform, or gaseous 

 matter, heated to such a degree as to be luminous." For the starting 

 and propagation of a flame in an explosive mixture, he showed that 

 each successive layer of gas must be raised to a certain definite tem- 

 perature, called the '' ignition point," and he investigated both the 

 ignition temperatures and the explosion limits of a large number of 

 the commoner combustible gases. He then proceeded to his famous 

 discovery that, notwithstanding the extremely high temperatures of 

 flames, which, in the case of cyanogen, he estimated to be "above 

 5000° of Fahrenheit," they can be readily extinguished by contact 

 with a cooling surface of sufficient area and heat-conducting power, 

 and that for this purpose metal surfaces are by far the most efficient . 

 How he developed and applied this discovery to the construction of 

 his " safe-lamp " for miners is, of course, a matter of history. 



In experimenting upon the ignition temperatures of explosive 

 mixtures, Davy made the important and far-reaching discovery that 

 combustible gases combine with oxygen at lower temperatures with- 

 out any appearance of flame whatever. He emphasised the import- 

 ance of a complete investigation of the chemical aspects of this 



