4 FORCE OF EXPLOSIVES IN GENERAL. 



But, supposing even that in an incomplete combustion, such 

 as that of gunpowder, no change in the chemical reactions were 

 produced, nevertheless the substitution of barium nitrate for 

 potassium nitrate would result in an increase of the absolute 

 weight of the mixtures, and consequently diminished pressure 

 and less heat evolved per kilogramme, for the reason that the 

 equivalent of potassium nitrate, KN0 3 being 101, and that of 

 barium nitrate 130'5, the weight of the oxidising agent neces- 

 sary to burn a given weight of combustible is increased one-third. 



The equivalent of sodium nitrate, NalSTOg, being 85, there will 

 be a less weight of it required than of potassium nitrate. 



The heat set free by this weight, which supplies an equal 

 amount of oxygen to the combustible, is, moreover, about the same. 



The substitution of sodium nitrate for potassium nitrate is 

 therefore advantageous in this respect. Unfortunately, the 

 hygroscopic properties of sodium nitrate are against its general 

 application. 



Copper nitrate, Cu(N0 3 ) 2 , would doubtless be preferable to any 

 other, because its equivalent is a little less than that of potassium 

 nitrate, and more especially as this salt, in its equivalent pro- 

 portions, supplies to the combustible bodies a fifth more oxygen 

 than the alkaline nitrates, in consequence of the total reduction 

 of the copper. This deserves attention, for potassium, sodium, 

 and barium remain after the explosion in the state of car- 

 bonates. By reason of this twofold circumstance, viz. the 

 lesser equivalent and the larger proportion of oxygen available, 

 the heat developed by the same weight of copper nitrate in 

 burning the same combustible is considerably in excess of that 

 produced by the alkaline salts. Unfortunately, copper nitrate 

 has such a strong affinity for water that it has hitherto been 

 found impossible to obtain it in the anhydrous form. 



Lead nitrate, Pb(N0 3 ) 2 , and silver nitrate, AgN0 3 , are, on the 

 contrary, easy to obtain anhydrous, and offer as oxidising agents 

 advantages equal, if not superior, to those of copper nitrate 

 when employed in equivalent proportions. 



But weight for weight this advantage no longer exists, 

 because their equivalents (165*5 and 171) are too high. The 

 price of silver nitrate would, moreover, militate against its 

 general adoption, and lead nitrate gives off very dangerous 

 fumes in confined places. 



It has been considered advisable to enter into these details 

 in order to show what a variety of conditions have to be 

 considered in order to produce an explosive applicable to a 

 particular class of work, and in which the nature and proportions 

 of the constituents are such as to develop the maximum effect. 

 In order to work successfully to this end it is necessary that all 

 experiments should be directed by certain laws deduced from 

 chemical and dynamical considerations. 



