On the Movements of the Flame in the Explosion of Gases. 471 



" On the Movements of the Flame in the Explosion of Gases." 

 By Harold B. Dixon, M.A., F.Pt.S. Eeceived and Eead 

 Jnne 5, 1902. 



(Abstract.) 



Part I. — Historical Introduction. 



Bunsen, in 1867, made the first careful measurement of the rate 

 at which an explosion is propagated in gases, and he also made the 

 first systematic researches on the pressure and temperature produced 

 by the explosion of gases in closed vessels. His results led him to the 

 remarkable conclusion that there was a discontinuous combustion in 

 explosions. When electrolytic gas, or when carbonic oxide with half 

 its volume of oxygen is fired, only one-third of the mixture is burnt, 

 according to Bunsen, raising the temperature of the whole to about 

 3000° C. No further chemical action then occurs until the gaseous 

 mixture falls by cooling below 2500°. Then a further combustion 

 begins, and so on, per saltum. These deductions were criticised by 

 Berthelot, who pointed out that they assumed the constancy of the 

 specific heats of steam and of carbonic acid at high temperatures. 



Bunsen also stated that the rapidity with which the flame of the 

 explosion spreads is synchronous with the attainment of complete 

 combustion and of the maximum temperature. 



In 1881 Berthelot and Le Chatelier independently discovered the 

 great velocity with which the flame travels in gaseous explosions. 

 Berthelot showed that this velocity was a constant for each gaseous 

 mixture, and compared the rate of the " detonation- wave " (Vande explo- 

 sive) with the mean velocity of the molecules produced by the combus- 

 tion before they had lost any heat. In theBakerian Lecture for 1893, 

 the author showed that Berthelot 's theory did not account for many 

 observed rates of explosion, and put forward the view that the explo- 

 sion-wave travelled with the velocity of sound in the burning gases. 

 Using the rates determined by the author, D. L. Chapman has 

 argued that, if the explosion-wave is of a permanent type, an equa- 

 tion can be deduced from Riemann's formula by which the rates of 

 explosion can be calculated if the specific heats are known, and vice 

 versa. The rate of the detonation-wave may therefore be utilised, 

 according to Chapman, to determine the specific heats of gases at very 

 high temperatures. 



In 1883 Mallard and Le Chatelier published their researches on the 

 combustion of gaseous mixtures. Using a delicate indicator, they 

 found that rapidly exploding gases gave very high pressures for very 

 small periods of time ; these high but fugitive pressures they attribute 



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