368 TRAJ^SACTIONS OF SECTION B. 



SECTION B.— CHEMISTEY. 

 Pbesident of the Section: — Professor W. A. Bone, D.Sc, P.E.S. 



WEDNESDAY, SEPTEMBER 8. 

 The President delivered the following Address : — 



Gaseous Combustion. 



This year is, as many of you are doubtless aware, the centenary of Davy's 

 invention of the Miner's Safety Lamp, which formed the starting-point of his 

 brilliant researches upon Flame, in which he disclosed and brought within the 

 range of experimental inquiry most of the intricate and baffling problems con- 

 nected with the fascinating subject of gaseous combustion. Also, the ground 

 on which we meet to-day is known to the whole scientific world as the place 

 where, during more than a quarter of a century of continuous investigation, a 

 succession of Manchester chemists, led and inspired by Professor H. B. Dixon, 

 have devoted themselves to the elucidation of the many problems which Davy's 

 work foreshadowed. Therefore, both in jaoint of time and place, the occasion 

 is singularly appropriate for a review of recent advances in this important 

 field of scientific inquiry. 



At the Sheffield Meeting of this Association in 1910 I had the honour of 

 presenting to a joint conference of Section A and B (Physics and Chemistry) a 

 Eeport summarising the then ' State of Science in Gaseous Combustion ' '■ 

 which gave rise to a keen and stimulating discussion, and was not only printed 

 in extenso in the Annual Eeport for that year, but was also widely circulated 

 through the medium of the scientific and technical press. There is no need, 

 therefore, for me to refer in any detail to the results of researches already 

 dealt with in that Eeport. I can more usefully devote part of the time at my 

 disposal to supplementing it with a review of more recent researches which 

 have considerably extended our knowledge in many directions. 



Ignition Phenomena. 



The first Section of my 1910 Eeport was concerned with Ignition Tempera- 

 tures and the Initial Phases of Gaseous Explosions, and it is in connection with 

 ignition phenomena that subsequent progress has been most marked. 



For the ignition of a given explosive mixture it is necessary that the 

 temperature of its constituents should be raised, at least locally, to a degree 

 at which a mass of gas self-heats itself by combination until it bursts into 

 flame ; or, in other -words, to a degree at which the chemical action becomes 

 autogenous or self-propelling, so that it quickly spreads throughout the whole 

 mass. This particular degree, or in some cases range, of temperature is 

 commonly spoken of as the ignition-foint of the mixture, but in using the 

 expression certain qualifications should be carefully borne in mind. In the 

 first place, as H. B. Dixon and H. F. Coward had shown in 1909," whereas when 

 certain combustible gases (such, for example, as hydrogen and carbon monoxide, 

 the mechanism of whose combustion is probably of a fairly simple character) and 

 air or oxygen are separately heated in a suitable enclosure before being allowed 

 to mix, the temperature at which ignition occurs lies within a very narrow 



1 Brit. Assoc. Eeport.':, 1910 (Sheflfield), pp. 469 to 505. 

 - Trans. Chem. Soc. 1909, vol. 95, pp. 514 to 543. 



