SALTPETRE AND SULPHUR. 491 



(1) Saltpetre and charcoal. The equation is the following 



4KN0 3 + 50 = 2K 2 C0 3 + 3C0 2 + 4K 



It corresponds to" 101 grms. of nitre and 15 grms. of carbon; in 

 all, 116 grms. ; or, for 1 kgm., 129 grms. of charcoal and 871 

 grms. of nitre. 



1. This being admitted, the heat liberated will be, for 1 equiv. 

 of potassium nitrate employed to burn carbon, at constant 

 pressure + 90*7 Cal., or + 91-2 Cal. at constant volume; or, for 

 1 kgm., 782 Cal. at constant pressure, or 786 Cal. at constant 

 volume. 



2. The reduced volume of the gases = 27*9 litres ; or, for 

 1 kgm., 240-5 litres. 



240-5 atm. 



3. Permanent pressure = - , with the usual reservation 



n 0*27 



relative to the liquefaction of carbonic acid. 



(2) Saltpetre and sulphur. The equation is the following : 



2KN0 3 + S 2 = K 2 S0 4 + S0 2 + 2K 



It corresponds to 101 grms. of nitre and 32 grms. of sulphur ; 

 in all, 133 grms. ; or, for 1 kgm., 241 grms. of sulphur and 759 

 grms. of nitre. The sulphur may be considered as pure, in 

 practice. 



1. The heat liberated will be, for one equivalent, 87'0 Cal. 

 at constant pressure, 8 7" 5 Cal. at constant volume; or, for 

 1 kgm., 654 Cal. at constant pressure, 658 Cal. at constant 

 volume. 



2. Keduced volume of the gases = 22*3 litres for the equi- 

 valent ; or 168 litres for 1 kgm. 



168 atm. 



3. The permanent pressure = , with the reservation 



n 0-25 



of the liquefaction limit of sulphurous acid. 



4. Theoretical temperature at constant volume, 3870. 



2545 atm. 



5. Theoretical pressure = . 



n 0'2o 



Note that under the conditions attending the use of black 

 powder the sulphurous acid shown by the above equations does 

 not appear. 



(3) Saltpetre, sulphur, and carbon, the latter in equal weights 

 (black powder with excess of nitre.) The equation of the reaction 

 is 



10KN0 3 +3S + 8C = 3K 2 S0 4 + 2K 2 C0 3 +6C(V 

 It corresponds to 505 grms. of nitre, 48 grms. of sulphur and 



1 Admitting the following specific molecular heats : C0 2 = 3'6 ; N = 2-4 ; 

 C0 3 K 2 = 151-0 ; S0 4 K 2 = 16-6 ; S0 2 = 3-6 (see p. 141). 



