94 



STUDIES IN LUMINESCENCE. 



Fig. 94 gives in graphical form a summary of the results of nine sets of 

 observations upon the decrease in maximum intensity of thermo-lumines- 

 cence with delay in heating. The curve G is from data plotted in Fig. 90. 

 In Fig. 95, which is from the same set of observations, the time of maximum 

 intensity is measured from the beginning of heating in order to exhibit 

 more clearly the shift of the maximum as the result of delay in beginning 

 heating. 



Table 16. 



Fig- 93- 



Curves similar to Fig. a.-?. Kxcited 40 seconds at 

 room temperature. Temperature of furnace 94 

 C. The time between the end of excitation and 

 the beginning of heating is as follows: 



Curve A, 1.9 sec:; curve B, 22.1 sec. curve C, 42.1 

 sec; curve D, 82.6 sec; curve E. 162. 1 sec. 



In Fig. 96 is shown the maximum intensity plotted against length of 

 excitation. These curves are similar to those shown in Fig. 89, but cover 

 a larger range of conditions. They indicate the same tendency to satu- 



Fig- 94- 



Decrease in maximum intensity 

 with delay in heating. The co- 

 ordinates are I* and time of I 

 measured from the end of excita- 

 tion. The length of excitation 

 and the temperature of the fur- 

 nace are as follows: 



Curve A, 320 sec, 93 C 



B, 40 sec, 92 C. 



C, 10 sec, 94 C. 



D, 320 sec, 202 C. 



E, 40 sec, 200 C. 



F, 10 sec, 200 C. 



G, 320 sec, 303 C. 

 //, 40 sec, 300 C. 

 /, 10 sec, 302 C. 



ration with increasing excitation whatever be the temperature and the 

 delay of heating; a point which would undoubtedly have been better 

 shown had a greater number of lengths of excitation been investigated. 



Fig. 97 shows the relation between maximum intensity and temperature 

 for the nine sets of runs. These curves correspond to those shown in Fig. 

 84. In some of the cases but one point can be given, the other runs show- 



