The Hate of Explosion in Gases. 



[Jan. 19, 



the presence of steam lias a marked effect on the rate. From 

 measurements of the rate of explosion with different quantities of 

 steam, the conclusion is drawn that at the high temperature of the 

 explosion wave, as well as in ordinary combustion, the oxidation 

 of the carbonic oxide is effected by the interaction of the steam. 



4. Inert gases are found to retard the explosion wave according to 

 their volume and density. Within wide limits an excess of one of 

 the combustible gases has the same retarding effect as an inert 

 gas (of the same volume and density) which can take no part in the 

 reaction. 



5. Measurements of the rate of explosion can be employed for 

 determining the course of some chemical changes. 



In the explosion of a volatile carbon compound with oxygen, the 

 gaseous carbon appears to burn first to carbonic oxide, and afterwards, 

 if oxygen is present in excess, the carbonic oxide first formed burns 

 to carbonic acid. 



6. The theory proposed by Berthelot that in the explosion wave 

 the flame travels at the mean velocity of the products of combustion 

 although in agreement with the rates observed in a certain number 

 of cases, does not account for the velocities found in other gaseous 

 mixtures. 



7. It seems probable that in the explosion wave 



(1) The gases are heated at constant volume, and not at constant 



pressure ; 



(2) Each layer of gas is raised in temperature before being 



burnt ; 



(3) The wave is propagated not only by the movements of the 



burnt molecules, but also by those of the heated but yet 

 unburnt molecules ; 



(4) When the permanent volume of the gases is changed in the 



chemical reaction, an alteration of temperature is thereby 

 caused which affects the velocity of the wave. 



8. In a gas, of the mean density and temperature calculated on 

 these assumptions, a sound wave would travel at a velocity which 

 nearly agrees with the observed rate of explosion in those cases 

 where the products of combustion are perfect gases. 



9. With mixtures in which steam is formed, the rate of explosion 

 falls below the calculated rate of the sound wave. But when such 

 mixtures are largely diluted with an inert gas, the calculated and 

 found velocities coincide. It seems reasonable to suppose that at 

 the higher temperatures the lowering of the rate of explosion is 

 brought about by the dissociation of the steam, or by an increase in 

 its specific heat, or by both these causes. 



10. The propagation of the explosion wave in gases must be ac- 



