for Equal Volumes unde?* Constant Pressure. 209 



that have been found, that a simple relation may also subsist 

 between the heat of motion of one atom ( = «) and the heat of 

 expansion. The numbers calculated for the foregoing approxi- 

 mately perfect gases approach (in general more closely in propor- 

 tion as Regnault's experiments are more trustworthy*, and the 

 gas in question at the same time follows Mariotte's law more 



ryl y 0*0691 



exactly) nearly the value ^ = — - = 0*0345. Conse- 

 quently I consider myself justified in substituting this numerical 

 value (which will hereafter have to be reduced to 0*03396), or 



in general -—~-^-, for a. According to equations (3) and (4), 



then, there exists for all perfect gases a simple constant ratio 

 among the three several parts of the specific heat under constant 

 pressure referred to equal volumes, namely the heat of expansion, 

 the heat of molecular motion, and the heat of atomic motion — that is, 



7 7 * 2 ' 2 

 or, since we have put — ~- —a, 



2a : 3a : na = 2 : 3 : n. 



Hence we have for the specific heat of all bodies in the state 

 of ideally perfect gases : — 

 For constant volume, 



y = na + 3a=(n + 3)a-, (6) 



for constant pressure, 



c/ = na + 3a + 2a=(n + 5)a. ... (7) 



If in equation (7) we put for 7' the mean value ( = 0*23773) 

 of the empirical specific heats of the approximately perfect gases 

 with diatomic molecules (oxygen, nitrogen, and hydrogen), we 

 have 



0*23773 = (rc + 5) «=7«. 



a = 0*03396 = 0-034 nearly. 



This numerical value introduced into equations (6) and (7) 

 gives 



7 =(n + 3).0-034, 



7 '=(rc + 5) .0*034. 



This specific heat y' of equal volumes of perfect gases under 



* Op. cit. p. 260. 



