248 BIOCHEMISTRY OF BACTERIAL LUMINESCENCE 



Such a reaction, if efficient, would convert thermal energy into a 

 portion of the energy in a light quantum and AF < hv. No objection 

 could be raised if R- and -OH were generated by independent 

 exergonic reactions and there seems no reason for assuming that reac- 

 tion 3 can distinguish the source of the reactants. 



Objections and Conclusions 



Despite the above arguments, if it could be shown that such a 

 mechanism violated either the first or second law of thermodynamics, 

 it would perforce be ruled out. It clearly does not violate the first law 

 since the total energy is constant. That the proposed mechanism does 

 not violate the second law is also clear on the following qualitative 

 grounds and is developed quantitatively in the succeeding quantita- 

 tive treatment. 



If it were possible to build a 100% efficient photoelectric or photo- 

 chemical device to convert the total light energy emitted by such a 

 proposed reaction mechanism into useful work, the second law would 

 be violated. Whether such a device could in principle be constructed 

 is the point at issue. Suppose a photoelectric device were to be 

 operated on light emitted as black body radiation by another body 

 at its own temperature. Since thermal energy is here converted into 

 light energy as an intermediate ( some, though a minute amount in the 

 wavelength region of bioluminescences!), if such a machine were 

 possible it would itself violate the second law. 



It follows from the above and following that the overall reactions 

 possibly leading to luminescence are not restricted to those having a 

 greater AF than hv. One cannot rule out as participants in and energy 

 sources for bioluminescences certain reactions less energetic than the 

 light emitted. 



On the Maximum Efficiency of a Photochemical Reaction* 

 Dr. Mayer: We consider the photochemical reaction: 



A + B^C -^hv (1) 



and consider that the free energy change 



-AF(°) = Fn(C) - F°(B) - F°(A) (2) 



* Dr. Joseph E. Mayer, of the Institute of Nuclear Studies, University of 

 Chicago, kindly contributed this paper, by invitation, for additional discus- 

 sion on the question at issue [Ed.h 



