94 Mr. D. L. Chapman on the 



cyanogen and oxygen, n is 2 and m is 3 : 



C 2 N 2 + 2 = 2CO + N 2 . 



(2 molecules) (3 molecules) 



I shall now calculate the energy lost when a gas is allowed 

 to burn and the products of combustion are collected at the 

 normal temperature and pressure. 



Assume that one of the gases is enclosed in the cylinder A 

 and the other in the cylinder B (fig. 2). These gases are forced 



out, burned at C, cooled at D, and collected in the cylinder E. 

 The gain of energy is the work performed by the pistons 

 a and b ; and the loss of energy is the heat evolved at D, 

 together with the work performed on the piston e. The total 

 energy lost is the difference of these. The volume of gas in 

 A and B is v ; therefore the work performed by the pistons 



a and b is p v Q . The volume of burnt gas is — - ; and 



therefore the work performed on the piston e is ■ ^° ° . 



The heat evolved at D is the heat of combustion at constant 

 pressure ; call it h. Let the total energy lost =H. 



Then 



H = A+/w>o(~l) 



During an explosion the whole of this energy is retained 

 by the gas, and in addition to this it gains an amount of 

 energy equal to the work performed on the gas. 



The energy of the exploded gas is therefore given by the 

 expression 



+ energy of exploded gas at N.T.P. 



n~Sf VYl 



= '1 + 15-2(0— VqY-PqV+PqVo- + energy at N,T.P. 



