HEAT OF DECOMPOSITION. 451 



On the contrary, in a miss-fire (progressive combustion) the 

 carbonic oxide increases and nitric oxide appears (p. 289). 

 We shall treat here only of the explosive combustion. 



16. Let us now calculate the heat liberated at constant 

 pressure. 1 According to equation (1), which corresponds to low 

 densities of charge, the reaction liberates 1230 Gal. (water 

 liquid), or 1140 Cal. (water gaseous). 



That is to say, for 1 kgm., 2 1076 Cal. (water liquid), or 9977 

 Cal. (water gaseous). 



According to equation (2), which represents the limit of re- 

 action for high densities of charge, we should have 1228 Cal. 

 (water liquid), or 1168 Cal. (water gaseous). That is to 

 say, for 1 kgm., 1074 Cal. (water liquid), or 1022 Cal. (water 

 gaseous). 



It will be remarked that the heat liberated is practically the 

 same according to equations (1) and (2). It therefore varies 

 but little with the density of charge, an observation which 

 appears applicable to explosive substances in general. Thus the 

 numbers 1074 CaL, and 1076 Cal., which correspond to the two 

 equations, are very close to each other, and also to the figure 

 1071 Cal. found by experiment. 



17. The volume of the reduced gases, calculated from equation 

 (1), will be 781 litres (water liquid), or 982 litres (water 

 gaseous) ; that is to say, for 1 kgm., 2 684 litres, or 849 litres. 

 Sarrau and Vieille found 671 litres, with a substance leaving 

 2 '4 per cent, of ash, which agrees. According to equation (2), 

 the volume of the gases will be the same, the water being sup- 

 posed liquid ; it would be raised to 743 litres per kilogramme, 

 the water being gaseous. Hence the volume of the gases does 

 not change much with the density of charge. 



18. The permanent pressure according to equation (1) 



(low densities) = -f- This formula is only applicable for 

 n 0*14 



densities - low enough for the carbonic acid not to be liquefied. 

 n 



16400 atm 



19. The theoretical pressure, from equation (1), = - 



fir 



From equation (2) = 1675 atm " 



Sarrau and Vieille actually found, by means of the crusher 

 and for densities of charge -, the following pressures, P' ex- 



7i 



pressed in kilogrammes : 



1 At constant volume these figures must be increased by one per cent. 



2 The substance supposed dry and free from ash. 



2 G2 



