EXPLOSIVES AND THEIR POWER. 



BOOK I. 



GENERAL PRINCIPLES. 



CHAPTEK I. 



FORCE OF EXPLOSIVES IN GENERAL. 



THE force of explosive substances is expressed by the pressure 

 which they exert, and by the work which they accomplish. In 

 a confined space, pressure results in the simple rending of the 

 envelope, without any subsequent work being effected. This is 

 exemplified by the fracture of a shell, through the freezing of 

 water contained in it, or the splitting of a rock by hydraulic 

 wedges. The effect of an explosive would be to disperse the 

 fragments of the shell, or to pulverise or displace the rock. 

 This subsequent action represents the mechanical work of the 

 explosive substance. 



The pressure is due to the gases evolved, and is dependent on 

 their volume and temperature. The work done depends princi- 

 pally on the amount of heat disengaged, which is a measure of 

 the energy developed. 



In other words, the maximum work that an explosive 

 substance is capable of producing, is proportionate to the 

 amount of heat disengaged during its chemical transformation. 



This may be expressed in kilogrammetres by the formula 

 425 Q, where Q is the number of units of heat evolved. 



This theoretical limit is never reached in practice, but still a 

 knowledge of it is indispensable, as it is the only absolute 

 point of comparison. 



The effective transformation of this energy into work, 

 depends on the volume of the gases evolved, the amount of heat 

 generated, and on the law of expansion. 



A fraction only of the energy can be actually realized in 



