[cale] 



DESTRUCTION OF FLUORESCENCE 



261 



Table 1 



Table 2 



Even a short exposure was sufficient to commence an operation 

 which caused complete decay within a few weeks for very dilute 

 solutions. Stronger solutions required two or three months. The 

 rate of decay in the dark was too small to exhibit any luminescene. 



Solutions exposed in quartz and glass gave curves of decay of 

 intensity of the same form, but as the glass only transmitted above 

 X = 3342^ some of the rays causing fluorescence were not available 

 in the case of glass and the rate of decay was about' half of that in 

 the quartz (Fig. 2). 



