f>8 DURATION OF EXPLOSIVE REACTIONS. 



The contrary will happen if the body be rapidly heated up to 

 the temperature corresponding to the most energetic reaction. 



7. In fine, the multiplicity of possible reactions involves 

 a complete series of intermediate phenomena, especially as, 

 according to the mode of heating, it may happen that several 

 decompositions will succeed one another progressively. This 

 succession of decompositions gives place to effects even more 

 complicated, as Jungfleisch has pointed out, when the first 

 decomposition, instead of producing a total elimination of the 

 decomposed part (changed into gaseous or volatile substances), 

 results in a division of the primitive substance into two parts ; 

 the one gaseous, which becomes eliminated, and the other solid 

 or liquid, which remains exposed to the consecutive action of 

 heating. The composition of this residue being no longer the 

 same which happens, for instance, with nitroglycerin which 

 has at first disengaged a portion of its oxygen in the form of 

 nitrous vapours the effects of its consecutive destruction may 

 be completely changed. 



8. Such are the causes, some chemical, some mechanical, 

 owing to which nitroglycerin and compressed gun-cotton each 

 produce such different effects, according as they are inflamed by 

 the aid of a body feebly ignited by a flame, by an ordinary 

 fuse, or again by the aid of a cap charged with mercury 

 fulminate. 



For example, Eoux and Sarrau have found that the necessary 

 charges for breaking a bomb shell, vary cceteris paribus, in an 

 inverse ratio to the following numbers, the value of which is 

 calculated by taking gunpowder as unit. 



Detonation. Inflammation. 



Nitroglycerin lOO 4-8 



Compressed gun-cotton 6-5 3-0 



Picric acid 5-5 2-0 



Potassium picrate 5-3 1*8 



The weight of the bursting charge with black powder, itself 

 under the influence of nitroglycerin primed with fulminate, has 

 been reduced in the proportion of 4'34 to 1. 



This inequality in the force of the same powder according to 

 the method of ignition, is also partially attributable to the 

 cooling produced by the walls in a slower reaction ; but 

 generally it results from a change occurring in the chemical 

 reaction. 



9. The diversity of the effects is less marked with non-com- 

 pressed gun-cotton, because the influence of the initial shock is 

 exercised on a smaller quantity of matter, and particularly 

 because the propagation of the successive reactions in the mass 

 develops therein weaker initial pressures and a less direct 

 transformation of energy into heat transmitted to the explosive 

 body. The cause of this is the interposed air. Consequently 



