T74 Mr. H. B. Dixon and Mr. J. C. Cain on the 



On the instantaneous pressures produced in the 

 Explosion-Wave. By H. B. Dixon, F.R.S., Pro- 

 fessor of Chemistry, and J. C. Cain, B.Sc, 1851 

 Exhibition Scholar in the Owens College. 



(Received May 22nd, 1894.). 



The problem of directly measuring the pressure pro- 

 duced in the ' explosion-wave ' of a mixture of gases is one 

 of great difficulty. The movement of the wave is so rapid, 

 and the zone of high temperature so thin, that the high 

 pressure over any given area lasts an exceedingly short 

 time. Nevertheless the problem is one of great importance 

 for the elucidation of the phenomena of explosion. 



To take one instance : If the pressure produced in the 

 explosion-wave could be accurately measured it would 

 decide between the two theories of gaseous explosions that 

 have been put forward. According to M. Berthelot* the 

 velocity of explosion is equal to the mean rate of translation 

 of the products of combustion heated at constant pressure. 

 In the alternative hypothesis^ the velocity of explosion is 

 equal to the velocity of sound in the burnt and burning gas 

 at a temperature double that due to the combustion of the 

 gases at constant volume. The calculated temperatures 

 and pressures of the explosion-wave are very different in 

 the two hypotheses. For example, in the explosion of 

 cyanogen with its own volume of oxygen the pressure in 

 the wave is calculated to be 35 atmospheres according to 

 the first view; it is calculated to be 117 atmospheres 

 according to the other. In the elaborate investigation 

 made by M. Berthelot, in conjunction with M. Vieille, on 

 the pressures produced in the explosion of gases, the 



*Sur la force des matiires explosives. 



+ H. B. Dixon, Phil. Trans., vol. 184., p. 134 (1893). 



