DYNAMICS OF LUMINESCENCE 153 



greater than the optimum. If that is the case, then lower- 

 ing the temperature should reduce the reaction velocity 

 to the optimum and light should appear. However, as we 

 have seen, not lowering but raising the temperature causes 

 luminescence with high oxygen concentration or high pyro- 

 gallol concentration. 



I believe the explanation of these phenomena lies 

 rather in another direction and that the effect of the tem- 

 perature and concentration of reacting substances affects 

 not only the reaction velocity but also the reaction prod- 

 ucts. While intensity of luminescence undoubtedly in- 

 creases with increasing reaction velocity, the luminescence 

 itself probably accompanies only one stage in the forma- 

 tion of a series of oxidation products. This stage is 

 favored at a definite temperature and mass of reacting 

 substances. Thus, in the oxidation of phosphorus several 

 intermediate oxides are said to be formed. The oxidation 

 takes place in steps and probably the luminescence is 

 connected with only one of the steps in a chain of reac- 

 tions. It is probable that a certain oxygen pressure and 

 temperature favors that particular step at the expense 

 of the others and so this oxygen concentration and tem- 

 perature correspond to the optimum for luminescence. 



The supposition that certain definite oxidation prod- 

 ucts of pyrogallol must be formed in order to produce 

 light is borne out by the fact that pyrogallol must be 

 oxidized in a particular way to obtain luminescence. The 

 blackening of pyrogallol with absorption of oxygen in 

 presence of alkali is a very well-known reaction, but 

 luminescence does not accompany this type of oxidation. 

 I have tried mixing all concentrations of pyrogallol and 

 all concentrations of alkali in an endeavor to obtain some 



