( 694 ) 



The results of the two investigators agree Avell. If one seeks from 

 the empirical equation of state for 0"0 C. the correction which must 

 be made on c^ at one atmosphere to reduce it to the ideal state, 

 one finds 0.003 cal., which quantity lies within the limit of experi- 

 mental error. The correction is still smaller for higher temperatures. 

 We also find that the correction, which is necessar^^ to reduce the 

 specific heat c^, of aether found by E. Wiedemann to the ideal state, 

 is too small to come into account. The formulae given by Regnault 

 and E. Wiedemann for the specific heat of gases and vapours are 

 thus applicable to tlie ideal state at least with close approximation. 

 Hence Leduc's contention ^) is refuted that for substances which obey 

 to the law of corresponding states both c, and c,- aie constant in the ideal 

 gas state. From the experimental values of r^ and the well known 



relation c — c,, = — , we can calculate the value of Cy and its variation 

 m 



with the temperature. 



Having found c„ in this manner we calculated the corrections 



which must be made to the equations (1) and (2) due to the variation 



of Cr. We find the following new values for the points on the liquid 



branch at t = 0.714 and t = 0.68 and for the solid phase at the 



triple-point 



points of the liquid state 



I. for t =r= 0,68 r= 0,83 



1] = — 117X10^ 

 B = — 286X10' 

 II. for t = 0,714 v = 0,85 



n=z— 96X10' 



r- = — 245X10^ 

 point of the solid state 



in. for t = 0,714 V = 0,676 



,j = — 180X10' 

 f =: — 420X10' 



Now we must investigate the liquid range for higher pressures 

 more exactly and in the first place determine Cv This follows from 

 the formula 



V 



V 



1) Leduc, Recherches sur les gaz. Paris 1898 and 99. 



