384 The Total Radiation from a Gaseous Explosion. 



gains by \mv 2 , and vibration is established, within or between 

 atoms, having also energy of ^mv 2 . 



The total radiation under these elementary conditions 

 should therefore be 25 per cent, of the energy of combination, 

 that is of combustion. 



2. A complete theory of explosion must account for both 

 the suppressed heat, found experimentally to be half that of 

 combustion, and the energy radiated, which has been observed 

 by Hopkinson and David to be 22 per cent, of the heat of 

 combustion*. In the theoretical case of two equal colliding 

 spheres these are respectively 50 and 25 per cent, of it. 

 This simple conception therefore appears to be capable of 

 explaining these two very important features of gaseous 

 explosion. No reason a priori has been given for the 

 radiation to be expected, and it is generally agreed that 

 specific heats do not vary sufficiently to account for the loss 

 of pressure. 



3. According to this mechanical view an explosion may 

 be regarded as 



(1) A process such as ionization by collision causing a 

 loosening of the bonds of the molecule of combustible 

 gas and of the oxygen molecule. 



(2) Attraction between ionized oxygen and combustible 

 * gas atoms resulting in a violent rush together, the 



total translational energy of which is the heat of 

 combustion. 



(3) Formation of products of combustion having a mean 



translational energy one half of that of the combining 

 atoms, mean additional energy ^, and vibrational 

 energy \ of it. 



4. The interchange of: energy between, say, rotation and 

 vibration appears to be slower than between translation and 

 rotation, for pressure is instantly checked in rising, whilst 

 radiation up to the time of maximum pressure is only 

 3 per cent, of the total heat of combustion f. While the 

 pressure remains nearly constant the gas continues to radiate, 

 and is therefore, in the absence of prolonged combustion, 

 receiving energy from the remaining degree of freedom, 

 rotation. Any excess of rotational energy is shared between 

 the other two terms, and in the process suggested there should 

 be both persistence of pressure and of radiation. 



* Phil. Trans. Roy. Soc. A. vol. ccxi. p. 375. 



f Hopkinson and David, loc, cit. 



