294 Mr Rideal, On the latent heats of vaporisation 



illumination of frequencies 2-3 lO^^ and 6-85 lO^'^, the respective 

 infra red and ultra violet activating frequencies. 



The appUcation of the hypothesis to the calculation of the 

 latent heat of evaporation of non-conductors is more difficult, 

 owing to our lack of knowledge of the intermolecular forces. The 

 latent heats are, however, all relatively small and the infra red 

 absorption bands generally well marked, thus CCI4 possesses a 

 marked absorption band at 4-5 /z equivalent to the value L = 6400 

 cal. per gm. mol. which agrees with the observed value of 



7100 - 700 = 6400 cal. 



In the case of naphthalene an absorption band would be antici- 

 pated at 3-36 /x, whilst actual observation indicates a strong ab- 

 sorption at 3-25 /z. In the case of water the complex infra red 

 spectrum leaves little doubt as to the existence of polymers in 

 solution. That the formation of di- and tri-hydrol takes place 

 through the oxygen atom is indicated by the equivalence of the 

 latent heat of evaporation to the interatomic energy provided by 

 a vibration frequency of 3-0 /z (9,540 cal. per gm. mol.) an absorp- 

 tion band which is always noted in compounds containing the 

 hydroxyl group. 



The so-called chemical constants of Nernst necessary for the 

 evaluation of the equilibrium constants and reaction affinities of 

 reactions occurring in non-condensed systems are related to the 

 undetermined constant of the vapour pressure formula by the 

 relationship 



^ i + log, R 



^ 2-3023 ' 



where i is the integration constant of the Clapeyron-Clausius 

 equation 



L^ _ d log P 



RT^" dT ' 



or dlogC ^L^-RT^ 



OT RT^ ' 



putting L^-RT = LQ + aT + ^T^ + ..., 



dT RT^'^ RT'^ '"' 



log,C = ^« + ~logT-t-*; 



or log, P=~^'+ {^1 log. T + ^-f+...i + log, R. 



When equilibrium is established between a hquid or solid and 



