472 



On the Induction of the Explosive Wave, &c. [June 16, 



XXIX. " On the Induction of the Explosive Wave and an 

 Altered Gaseous Condition in an Explosive Gaseous Mixture 

 by a Vibratory Movement." By Lewis T. Wright. Com- 

 municated by Professor Odling, F.R.S. Received June 13, 

 1887. 



(Abstract.) 



The author refers to the conclusions of Berthelot and Vieille that 

 the phenomenon of the explosive wave is quite distinct from that of 

 ordinary combustion, each being marked by well-defined limits called 

 by them the regime of detonation and combustion respectively. The 

 transition from the one to the other is accompanied by violent vibra- 

 tory movements. 



Mallard and Le Chatelier separate the combustion of an explosive 

 mixture inflamed at the open end of a tube, closed at the other, into 

 four different and succeeding phases — 



(1.) Uniform propagation of flame ; 

 (2.) A vibratory movement ; followed in some cases by 

 (3.) The explosive wave of Berthelot and Vieille. 

 (4.) Spontaneous extinction of flame. 



The author has specially studied the connexion between the vibrating 

 stage and the explosive wave with a certain mixture of coal gas and 

 air (in large glass tubes) which sharply exhibits the various features 

 of the four stages described by Mallard and Le Chatelier. 



The points determined were these, that the detonating stage (explo- 

 sive wave) is never initiated without preceding vibratory movements 

 on the part of the flames. 



That with the same mixture the vibrating period is of definite 

 duration culminating in the explosive wave stage. 



The necessary connexion between the two stages being proved, the 

 author investigated the question whether the explosive wave condition 

 is communicated layer by layer by the contact of the flame itself, or 

 whether the whole column of unignited gas in the tube adjacent or 

 distant from the flame is "induced" by the vibrating flame into a 

 more receptive condition which enables the chemical reaction between 

 the molecules to proceed at a more rapid rate than usual. 



The phenomena exhibited by the flame suggest this latter explana- 

 tion, and the author by the application of a weak spark test has been 

 enabled to prove that the whole column of gas, either adjacent or dis- 

 tant from the vibrating flame, is in an altered condition after being 

 submitted to but a portion of the vibratory action which normally 

 initiates the explosive wave. 



