750 Mr. J. G. Stewart on the Inapplicability of 



Part II. 

 Discussion of the Errors involved in the determination of the 

 Specific Heat of Gases at High Temperatures due to an 

 assumption of the truth of Boltzmanns Hypothesis* . 



Three methods have been used to determine the specific 

 heats of gases. Of these two are liable to error due to the 

 false assumption of the truth of Boltzmann's hypothesis 

 under conditions of changing internal energy. 



(1) Constant Pressure method or Regnault' s method. — By this 

 method the gas at atmospheric pressure is heated to a chosen 

 temperature and its heat then measured by passing it through 

 a calorimeter. In this method the gas at inlet and outlet 

 has a constant pressure and temperature, and therefore 

 Boltzmann's hypothesis will be true. This method was used 

 bv Holborn and Henning in their work. 



(2) Constant Volume method. — In this method a known 

 explosive mixture is put into a containing vessel and exploded. 

 A record of pressure and time is taken as represented by the 

 curve 012 3 (fig. 2). 01 and 3 2 are produced to meet 



at P. The true maximum pressure of the explosion is taken 

 as that indicated by P after applying a correction for cooling, 

 which correction is taken from the cooling curve 2 3. The 

 heat generated in the explosion and the initial pressure and 

 temperature are known ; the maximum temperature can be 

 obtained from the gas equation pv = RT. The mean specific 

 heat for the burned gases can then be found by calculation. 

 From the point of view of this paper this method is 



* For present state of knowledge of Specific Heats see British Asso- 

 ciation Keports of Gaseous Explosions Committee 1908, and subsequent 

 years. 



