studies in luminescence;. 



layer of the solution of fluorescein is viewed by reflected light its color is 

 green, whereas the fluorescence of a mass of the liquid appears decidedly 

 yellowish. This change is shown graphically in the curves of Fig. 5. In 



60 80 .500/' 20 40 60 



Fig. 4. Fluorescein. 



Typical fluorescence spectrum (EE). 



this figure A is the transmission curve of the solution; B is the observed 

 curve of fluorescence when the slit through which the excited light enters the 

 cell is placed so that the fluorescent light passes through 0.055 cm - f the 



.4 50/^ 60 70 



80 90 .500/' 10 20 30 



Fig. 5. Fluorescein. 



-10 50 60 70 



IvMect of absorption upon the fluorescence spectrum. 



solution before exit ; and C is the fluorescence curve when the slit is shifted 

 to such a position that the fluorescent light passes through i cm. of the solu- 



