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CHAPTER II. 



GENERAL DATA RESPECTING THE EMPLOYMENT OF A GIVEN 

 EXPLOSIVE. 



1. THEORETICAL DATA. 



1. EXPLOSIVE bodies cannot be employed profitably and securely 

 unless they are characterised by a certain number of data, 

 theoretical as well as practical, which will now be enumerated. 



2. First as regards theoretical data. They have been given in 

 principle in Book I. ; but it seems desirable to summarise them 

 here from a more special point of view. These data refer to 

 eight orders of measurements, namely : 



(1) The chemical equation of transformation. 



(2) The heats of formation of the components and products. 



(3) Their specific heats. 



(4) Their densities. 



(5) The pressures developed. 



(6) The initial work which determines the reaction (tempera- 

 ture of inflammation, nature of shock, etc.) 



(7) The law which determines the rapidity of the transforma- 

 tion with reference to temperature and pressure. 



(8) The total work which an explosive substance can effect 

 (potential energy). 



Each of these orders of measurements embraces several dis- 

 tinct determinations. 



3. The chemical equation of the explosive transformation 

 comprises : 



(1) A knowledge of the original bodies and of the products as 

 regards their nature and relative weight. 



(2) The knowledge of the volume of the permanent gases, re- 

 duced to and 0*760 metres, which the transformation develops 

 (p. 18). This volume may be calculated a priori, or measured 

 directly and as an essential element of chemical analysis. 



(3) A knowledge of the gaseous volume (reduced by calculation 

 to and 0*760 metres) of the products actually liquid or solid, 



2B2 



