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XXVI. Studies on Gases. 

 By Dr. H. W. Schroeder van der Kolk. 



[Concluded from p. 137-] 

 § VI. On the Difference of the Specific Heats. 



PTPHE same formula which, if — is known, gives the value of 



the mechanical equivalent of heat, can, conversely, be used for 

 calculating Cj — c for different gases under different pressures and 

 at different temperatures. c l —c is then the unknown quantity 

 in the formula 



,2 



c, — c= 





dk dk dk 



the determination of -r- or -7- and -t- is effected by means of 

 dt dr dp J 



the formula previously found. 



Hydrogen. 



In the case of hydrogen, k } as has been observed, is indepen- 



dk 

 dent of the temperature, and hence -7- =0. The formula be- 

 comes therefore 



k 



c,—c= 



V k dp) 



dk 



-7- is determined by means of the formula in § II. We have 



in which A, B, and K have the values there given. We have 



0*76 metre. 1 metre. 2 metres. 

 Cl -c 1-00075, 1-00093, 1-00183. 



This difference increases, therefore, with the pressure, and, within 

 the limits of the accuracy of Reguault's experiments, must be 

 considered independent of the temperature. From this it fol- 

 lows that either c x or c, or both, change with the temperature. 



Air. 



In the case of air, c 1 — c may be calculated for different pres- 

 sures and temperatures. As regards the change of k with the 

 Phil. May. S. 4. Vol. 31. No. 208. March 1866. O 



