THE DETONATION PROCESS 



81 



librium calculations in all cases agree better with experiment than the 

 quantitative reaction. The agreement is, on the whole, extremely good 

 and gives considerable support to a conclusion that detonation condi- 

 tions are best calculated on the basis of equiUbrium of the products. 

 This result seems somewhat paradoxical when it is considered that the 

 thickness of a shock or detonation front is estimated as less than 10^^ 

 cm., which for a velocity of the order 3 X 10^ cm. /sec. allows a time of 

 10~^ sec. or less for reaction in the front. It is of course unreasonable 

 to expect completion of the reaction in such a small time. The success 

 of the equilibrium calculation indicates rather that the reaction is essen- 

 tially complete before the conditions behind the shock front have 



Table 3.1. Calculated and measured detonation velocities in gaseous mixtures. 



changed enough to invalidate the procedure. It should be mentioned 

 that the detonation velocity is probably less sensitive to such errors 

 than are the pressure and density immediately behind the front, and 

 such values may be less accurate. 



B. The calculations of Jones. The reactions of solid explosives are, 

 of course, practically much more important than those in gaseous mix- 

 tures and present greater difficulties because of the higher temperatures 

 and densities. A first approach to the question of a suitable equation 

 of state for such conditions is to assume a modified Van der Waals equa- 

 tion of the form 



P{V -h) = 



RT 

 M 



in which h, the covolume constant, represents in elementary kinetic 

 theory four times the total molecular volume from which molecular 

 motion is excluded. This type of equation has been used by various 

 workers in the past to represent explosion products of closed bomb ex- 



