DYNAMICS OF LUMINESCENCE 145 



The effect of temperature on luminescence is of special 

 interest because it gives us a means of analysis for deter- 

 mining if the luminescence depends on reaction velocity. 

 We know that photochemical reactions are very little 

 affected by temperature because the reaction is dependent 

 on the absorption of light, a physical process, and this 

 increases only a small per cent, for a rise of temperature 

 of 10° C. To put it in the usual way, its temperature 

 coefficient (Qi,,) for a 10° interval is usually less than 1.1. 

 On the other hand, we should expect photogenic reactions, 

 in which some of the chemical energy is converted into 

 radiant energy, to give off much more light the 

 greater the reaction velocity. As reaction velocity in- 

 creases so rapidly with temperature (Qj,^^2 to 3), 

 luminescence intensity should rapidly increase with 

 increase in temperature. 



Trautz (1905), from his extensive study of the chemi- 

 luminescence of phenol and aldehyde compounds came to 

 the conclusion that luminescence intensity was propor- 

 tional to reaction velocity. He based his conclusions 

 largely on the effects of temperature and concentration of 

 reacting substances and went so far as to declare that any 

 reaction would produce luminescence if the reaction veloc- 

 ity were sufficiently increased. It is quite true that increas- 

 ing the temperature does increase the intensity of chemi- 

 luminescence, but this is only within certain limits. As 

 we raise the temperature, chemiluminescence becomes 

 more intense but we soon reach a temperature for maxi- 

 mum luminescence and above this the intensity diminishes. 

 This is especially well seen in the action of various 

 oxidizers on pyrogallol and H2O2 recorded in Table 10. 

 At 100° C. practically no light is produced by many 



