M. Achille Cazin on Internal Work in Gases. 273 



v =0*50571 cub. m., 

 T =273°, 

 ^ = 283°, 

 K=017. 



This value of K is the specific heat at a constant volume and 

 a high temperature. According to M. Hegnault, the specific 

 heat at constant pressure is 02396 towards 200°. If the ratio 

 of the two specific heats were 1*29, as it seems to be at the ordi- 

 nary temperature*, K would be equal to 0*18. But it is not 

 proved that this ratio does not increase with the temperature. 

 M. Hirn took 0*164 for the value of K. By taking 0*17 I do 

 not think a very large error is made. 



With these various data the formula (7) leads to 



T'=280°, 

 whence 



Having T' and v\ the pressure p r in millimetres of mercury 

 can be calculated by means of the formula (6), in which p =z 760 

 millims. It is found that 



p'=z 753*15 millims. 



In the same manner, by introducing into this formula the 

 values of Tj, v 1 we shall have, for the initial pressure, 



jt?j=3572 millims. (4*7 atmospheres). 



Suppose that after the expansion the heat of the sides reesta- 

 blishes the temperature T x in the gaseous mass. Then the pres- 

 sure, which was p\ will become p ; and this value may be cal- 

 culated by introducing T ]? v 1 into formula (6) ; we obtain 



p = 761-30 millims. 



Thus one kilogramme of carbonic acid at 10° and under a 

 pressure of 4*7 atmospheres expanding, without external work 

 and without transmission of heat, to the pressure of about one 

 atmosphere (753*15 millims.), undergoes a spontaneous fall of 

 temperature of 3°. When it afterwards resumes its primitive 

 temperature by the action of the sides, its pressure rises 



p — y = 8*15 millims. 



The example just given furnishes some numbers quite compa- 

 rable with those given by my experiments. 



* A. Cazin, " Essai sur la detente et la compression ties gaz sans varia- 

 tion de chaleur," Annates de Chimie et de Physique, S. 3. vol. lxvi. p. 206 



(1862). 



