Boltzmann s JEquipartition Hypothesis. 751 



interesting because the gases are under very rapid change of 

 temperature. 



Suppose Oab (fig. 3) to represent an ideal pressure-time 

 curve for an explosion throughout which static equilibrium 

 has been established at each point. We can consider the 

 effect of a lag in the gas in reaching this equilibrium state. 



Fiff. 3. 



During the explosion period an excess amount of energy will 

 be in the form of internal molecular energy, since this is the 

 first result of chemical action, translational motion coming 

 later. The actual pressure curve 01 will therefore fall below 

 the ideal. At time al explosion is complete, but the gas has 

 not yet attained an equilibrium state. As this equilibrium 

 state is established, the pressure rises to ultimate coincidence 

 with ah. It will be observed that the producing of 01 and 

 12 to P gives too low a maximum pressure and consequently 

 too high a value of the specific heat. This is borne out by 

 results ; comparing specific heats obtained by this method 

 with those obtained by the constant pressure method, it is 

 found that the explosion method gives values as much as 

 10 per cent, higher than the other. Mallard and Le Chatelier 

 and Langen have used the explosion method. It should be 

 noted that lag in the gas in attaining its equilibrium state 

 gives an explanation of the rounded top 1-2, which cannot 

 adequately be explained in any other way. 



(3) In the third method both the pressure and volume are 

 varied. This method is due to Mr. Duo-aid Clerk. He 

 successively compressed and expanded a volume of gas in 

 a gas-engine cylinder, obtaining the indicator diagram 



