Instantaneous Pressures in the Explosion- Wave. 179 



An indirect way of arriving at the pressures in the 

 explosion-wave is given by Riemann's* equation for the 

 propagation of abrupt variations in the density and pressure 

 of a gas. Professor Schuster f has given reasons for sup- 

 posing that Riemann's equation applies for the explosion- 

 wave, and has shown a simple way of calculating the 

 pressures from the known velocity of the explosion-wave 

 and the density of the unburnt gas. According to Rie- 

 mann's equation the pressure in the explosion-wave of 

 cyanogen and oxygen should be 135 atmospheres, and when 

 diluted with its own volume of nitrogen the pressure should 

 be 71 atmospheres. The calculated and observed pressures 

 may be conveniently compared in the annexed table : — 



Pressures in the Explosion-wave. 



Gaseous Mixture. 



Calculated. 



Observed. 



Berthelot. 



Dixon. 



Riemann. 



Berthelot. 



Dixon 

 & Cain. 



C 2 N 2 + 2 

 C2N2+O2+2N2 



35 At. 

 18 „ 



117 At. 

 57 » 



135 At. 



125 At. 

 15 11 



70 — 120 



63— 84 



It will be observed that the pressures calculated by 

 Riemann's equation are about 4 times greater than those 

 deduced from Berthelot's Theory : and are larger (roughly 

 by 20 per cent) than those calculated from Dixon's 

 They agree within the limits of error with our observations 

 on the breaking strain of glass tubes. 



Experiments on the Collision of Two Explosion-waves. 

 The apparatus we employed could readily be adapted 

 to observe the effect of bringing two explosion-waves into 

 collision. Will the result of two waves meeting from 



* 'Gottingen Abhandlungen.' 8. (i860). 



t Vide Phil. Trans. Vol. 184, p. 152. (1893). 



