Energy Increment and TroutorCs Huh. 157 



Hesse shall hold, Q the heat of reaction being determined 

 from the relationship 



^ = "^ '^products ~~ V reactants>* 



The calculation of" the critical energy increments from 

 temperature coefficient data in many cases leads to a value 

 of v a frequency for which the substance shows no 

 absorption band or line. This fact has led Langmuir 

 (J. A. C. S. xlii. p. 3190, 1920) to reject the whole concept 

 of a relationship between radiation and molecular activity. 



In the case of the formation of ozone (loc. cit.) it was 

 noted that the oxygen molecules could undergo at least 

 two stages in activation — one in the infra-red and one 

 in the ultra-violet, — and it was pointed out that the critical 

 energy increment would vary with the nature of the mole- 

 cules to be activated. If inactive molecules were used, the 

 critical energy increment would be E = ~Nhp u , Vm , whilst if 

 molecules already activated to the infra-red stage were taken 

 the critical energy increment would be IT=N/*(z> m . u .--j> 1 >.), a 

 value somewhat smaller than the former. 



Tolman (J. A. C. S. xlii. p. 2506, 1920), treating the 

 problem by the method of statistical mechanics, has also 

 come to the conclusion that a widely extended range of 

 activating frequencies is a perfectly tenable hypothesis. 



The critical energy increment is thus an average value of 

 the amount of energy to be supplied to cause a gm. mol. to 

 become reactive for a particular reaction. In any system some 

 molecules would already be activated to the necessary extent^ 

 whilst others would require activation from an inactive state, 

 i. e. would require a large energy increment. Between 

 these two extreme types of molecules there exist molecules 

 with varying degrees of activation, the energy content of 

 each varying by steps according to the relationship e = hv, 

 where v corresponds to the various lines in the absorption or 

 emission spectrum of the substance. The mean value of v 

 as determined by the method of temperature coefficient may 

 thus in some cases have no real significance. 



The various degrees of activation of a molecular species 

 can be calculated from the bands or lines in the absorption 

 or emission spectrum and may possibly, according to 

 Baly (B. Assoc. Reports, 1920, p. 31), be multiples oi' one 

 characteristic value Vi, r .. The characteristic ultra-violet 

 frequencies of the elements and the resonance potentials 

 of the gases give values which scarcely appear to be in 

 harmony with this view, although the very large differences 



