BERNARD L. STREHLER 249 



is known for the chemical reaction with the reactants and products at 

 unit concentration. 



The reaction may actually go to emit a range of frequencies, hv, 

 but we suppose the mechanism for the emission of any single fre- 

 quency vo to be such that one molecule of A plus one of B follow 

 some successive steps to emit one quantum, /7i'o, uncoupled with any 

 parallel steps by which molecules A and B react, either without the 

 emission of light, or with emission of lower frequencies /. The rate 

 Ro of photons of frequency r-o, per unit frequency range, per cubic 

 centimeter, at unit concentration of A, B, and C is now measured: 



Rodi'dV — number of photons of frequency between vo and vo + dv 

 emitted by the reacting mixture of volume dV, at temperature T, with 

 A, B, and C at unit concentration. 



The question now is: What is the maximum value of Ro for any 

 frequency, vo at T, in terms of the free energy liberation, — aF"", of 

 the chemical reaction? 



The question can be answered by considering the following hypo- 

 thetical reversible machine. 



We place the reacting mixture, at temperature T, unit concentration 

 of A, B, and C in a vessel and, with a negative catalyst, inhibit any 

 reaction which emits other frequencies than vo, or which does not 

 emit light. Since the reaction which emits vo is supposed to be un- 

 coupled to any other reaction, this fiction is permissible and is equiva- 

 lent to the assumption of microscopic reversibility. 



We surround the reaction vessel with an insulating wall, transparent 

 to the frequency vo, but to no other radiation. The space outside of 

 this contains black body radiation enclosed in completely reflecting 

 walls, fitted with a completely reflecting piston, so that by compression 

 or expansion, the temperature T* of the radiation can be altered. 



An auxiliary machine can be used to remove radiation from the 

 reservoir at T*, by adiabatic expansion to the temperature T of the 

 reacting mixture it can obtain useful work, and deliver the remaining 

 radiation to a reservoir at T. This process can be carried out reversibly, 

 the useful work AW, obtained from the radiant energy a£* taken out 

 at T*, is 



^={T*-T)jT* (3) 



By adjusting the temperature T* of the surrounding black body 

 radiation, we can keep the radiation density C7(vo) in the reaction 



