Lost Pressure in Gaseous Explosions. 



21 



that the velocity of a travelling wave corresponds to a 

 temperature in the wave-front twice that derived from the 

 heat liberated by slow combustion. Chapman has calculated 

 the specific heats of the products from the wave velocity, and 

 has obtained values nearly twice as high as those at low 

 temperatures. Berthelot has remarked that the pressure 

 indicated by any moving mechanism is probably not that 

 in the wave-front but on i corresponding to ordinary com- 

 bustion. 



If, however, the translational energy is suppressed for a 

 moment by one half in the act of explosion, as shown above, 

 the observed maximum pressures are the theoretical maxima 

 and the difficulty of reconciling theory and observation is 

 removed. 



(3) Experimental values of the Explosion Pressure 

 ratio approximate to \, 



The ratio of the observed to the theoretical maxima, 

 calculated on the assumption that all the energy of slow 

 combustion is converted into translational energy in explosion, 

 closely approaches one half. 



In the case of hydrogen and air the observed and cal- 

 culated values are as follows * : — 



Table I. 



Percentage of Gras 

 in Air. 



Maximum Pressure of Explosion in lbs. 

 per square inch. 



Observed. 



Calculated. 



Ratio. 



14-3 



41 



68 

 80 



88-3 



124 



176 



•465 

 •549 

 •455 



200 



28-5 









Mean... 



-489 







In two cases of coal-gas and air Dr. Clerk obtained the 

 following values f. 



* P. Clerk, ■ The Gas, Petrol and Oil Engine,' vol. i. p. 105. 

 t Loc. cit. p. 136. 



