492 POWDERS WITH A NITRATE BASE. 



48 grms. of carbon ; in all, 601 grms. ; or, for 1 kgm., 840 grms. 

 of nitre, 80 of sulphur, and 80 of charcoal. 



1. The heat liberated will be for the equivalent weight, 

 479-6 CaL at constant pressure, or 481'2 Gal. at constant 

 volume; or, for 1 kgm., 798 Cal. at constant pressure, and 

 801 Cal. at constant volume. 



2. Eeduced volume of the gases = 66'9 litres for the equiva- 

 lent weight ; or 111/3 litres for 1 kgm. 



3. The permanent pressure = _ ', with the reservation of 



Ti-0'27 



the limit of liquefaction of carbonic acid. 



4. Theoretical temperature, 4746. 



2046 atm. 



5. Theoretical pressure = . 



n 0'27 



6. The heat produced slightly exceeds that of sporting and 

 service powder. But the volume of the permanent gases 

 developed by the latter is double that corresponding to a 

 complete combustion. Hence the pressure is far lower for 

 powder with excess of nitre than for -sporting and service 

 powders. 



The complete combustion effected by an excess of nitre is 

 therefore not advantageous from the point of view of the effects 

 developed by the pressure of powder. This inferiority of 

 powder with an excess of nitrate had already been discovered 

 in practice. 



7. However, it is worthy of remark that the compounds 

 which are formed by the complete combustion of a powder with 

 an excess of nitre, viz. potassium sulphate and carbonate, are 

 also noticed by writers on the subject as principal products 

 in the deflagration of sporting and service powder, as well as in 

 that of powders the most different in appearance, such as 

 blasting powder, which is very rich in sulphur, and powder 

 with an excess of charcoal. Although the products vary a little 

 with the conditions of deflagration, potassium sulphate and 

 carbonate have almost always been observed, and this is the more 

 important, as these two salts do not figure in the theoretical 

 equations formerly admitted. 



7. SERVICE POWDERS. 



1. We shall divide the study of service powders into four 

 sections, comprising 



(1) The general properties of powder. 



(2) The products of combustion of powder. 



(3) The theory of combustion of powder. 



(4) The comparison between theory and observation. 



