as applied to Gases and Vapours. 531 



and /(D). Then from equation (21) we deduce the following 

 results : — 



So=J(l-^»+So/o) 



„ 1 /, , 100° A. „ ^\ 



^'- p V+ "c~ ~ cTioo^ +^^f')' 



and consequently 



E'= ^"~ 



100° s. 



SoPVc 



+ 



Ai 



So/o^Sj/i 



C^IOOC 100(C + 100) 100 



). . (30) 



In applying the empirical formulae (25), (26), and (28) to de- 

 termine the values of Aj and Sj/j in the above equation, it will 



produce no appreciable error to use ^ Dq as an approxi- 



mate value of D^, for that purpose only. By making the neces- 

 sary substitutions, the following formulae are obtained : — 



For Carbonic Acid, 



where log a =5*51 89349. 

 For Atmospheric Air, 



E' 



~ nMV I C "^ \nM/ ^ ' \nM.J J' 



(31) 



where log «= 5-4717265 

 log ^=6-9759738 



(28.) The following table exhibits a comparison between the 

 results of the formulae and those of M. Regnault^s experiments. 

 It is not, like the preceding table (article 25), the verification of 

 empirical formulae, but is a test of the soundness of the theo- 

 retical reasoning from which equations (30) and (31) have been 

 deduced. 



It is impossible, from the want of a sufficient number of ex- 

 perimental data, to give a formula similar to (31) for hydrogen. 

 I have calculated, however, the value of the coefficient E' for that 

 gas, corresponding to the pressure of one atmosphere, on the 

 assumption that at that pressure a formula similar to that for 

 carbonic acid gas is applicable without sensible error. 



