THEORETICAL TEMPERATURE AND PRESSURE. 501 



5. The chemical transformation of powder being thus defined, 

 let us now calculate the heat liberated and the volume of the 

 gases produced, according to each of the five equations regarded 

 separately. 



6. Equation (1), 



2KN0 3 -f S + 30 = K 2 S + 3C0 2 + 2T, 



represents 135 grms. of matter ; or, for 1 kgm., 784 grms. of 

 nitre, 118*5 grms. of sulphur, 133-3 grms. of carbon. The 

 products being, 408 grms. K 2 S, 488 grms. C0 2 , 104 grms. K. 



The reaction liberates + 734 Cal. at constant pressure, 74'5 

 at constant volume, a quantity which the formation of the 

 polysulphide, K 2 S 2 , by an excess of sulphur during cooling 

 would raise to about 77 Cal. 1 This figure itself is calculated 

 with the aid of data obtained at the ordinary temperature. At 

 the high temperature of the explosion it is modified by various 

 circumstances, such as the partial dissociation of the carbonic 

 acid, the state of fusion, or even of volatilisation, of the 

 potassium sulphide, the variation in the specific heats, etc. 

 But it is not possible in the present state of the science to take 

 these various circumstances into account; we shall therefore 

 confine ourselves to the calculation based upon the data 

 observed. These remarks apply likewise to the other equations. 



Supposing, therefore, -f 73 '4 or 74*5 liberated by the trans- 

 formation (1) ; this quantity, referred to 1 kgm., becomes 544 

 Cal. at constant pressure, or 552 Cal. at constant volume. 



The reduced volume of the gases is 44*6 litres, or, for 1 kgm., 

 330-4 litres. 



330-4 atm. 



Permanent pressure = , with the usual reservation 



n 0*1^ 



of the liquefaction of carbonic acid for small values of n. 

 Theoretical temperature 2 = 3514. 



4592 atm. 5740 atm. 

 .Theoretical pressure 8 = nTTo""' r ' assuming 



the total vaporisation of the potassium sulphide. 



1 It is here supposed that C + 2 = C0 a liberates + 47-0 Cal. See remarks 

 on page 488. 

 8 The following specific heats are taken 



C0 2 3-6 (at constant volume) 



N 2-4 



CO 2-4 



ILS 8.0 



C0 3 K 2 15-0 



BOA 16-6 



They are supposed constant for the sake of simplicity. 



3 The real density of sulphide of potassium not being known, a density 

 nearly equal to 3 has here been taken. 



