SENSITIVENESS OF EXPLOSIVES. 37 



The author has, moreover, developed the whole of this theory 

 in another place, 1 and recalls it in order to thoroughly fix the 

 ideas. 



5. It plays a very important part in the explanation of the 

 mode of formation of the secondary compounds, produced by the 

 explosion of powder, several of these compounds being formed 

 at the very outset, at temperatures which would gradually 

 destroy them if they lasted long enough. But the suddenness 

 of the cooling keeps the compounds, such as formic acid, 

 ammonia, nitric acid, from the destruction which they would 

 quickly undergo if they were maintained in a constant manner 

 at the initial temperature of their formation. In fact, this sudden 

 cooling brings them to the temperature at which they are defi- 

 nitely stable. 



3. SENSITIVENESS OF EXPLOSIVE SUBSTANCES. 



1. This sensitiveness depends both on condition of heating, 

 and on the mode of propagation of the reactions. It varies 

 according to circumstances. One substance is sensitive to the 

 slightest rise in temperature, another to a sudden pressure, 

 another to shock, properly so called, another detonates with the 

 least friction. Thus for example, silver oxalate detonates at 

 about 130, nitrogen sulphide at about 207, mercury fulminate 

 at a temperature near this, about 190, and nevertheless the 

 fulminate is much more sensitive to shock and friction than 

 nitrogen sulphide and silver oxalate. There exist therefore 

 special properties, depending on the individual structure of each 

 substance, particularly for the solids, which favour decomposi- 

 tion under given circumstances. But there also exist general 

 conditions, which it will now be useful to state. 



2. The sensitiveness exhibited by the same substance 

 increases with the initial temperature at which the operation 

 is performed, that is, a temperature nearer to that at which the 

 body commences to be spontaneously decomposed, the explana- 

 tion of this being that the heat liberated by the reaction proper 

 undergoes less loss by radiation, and that it raises to the desired 

 degree a greater weight of the non -decomposed substance. 



A portion of the sensitiveness will be rendered still greater 

 if this limit be exceeded, that is, if the conditions prevail under 

 which a slow decomposition may be transformed by the least 

 heating into a rapid decomposition. 



A substance taken near and especially above this limit may 

 be said to be in the state of chemical tension. 



For example, celluloid, a body which does not detonate 

 under the hammer at the ordinary temperature, acquires the 

 property of detonating when heated to about its softening point, 

 1 " Essai de M^canique Chimique," torn. ii. p. 58 and following. 



