STUDIES IN LUMINESCENCE. 



(about 0.595 n) remains constant for all dilutions. The shift in the observed 

 fluoresence maximum is therefore due entirely to absorption. 



This fixed position of maximum fluorescence seems to be consistent 

 with the theory of ionization. According to Buckingham, ions may have 

 some of the same optical properties as other substances and fluorescence 



C 



ISO 



100 



50 



0) 



> 





Fig. 35- 



0.55/X 0.60/1 



Fig. 36. 



0.6 Sp 



Variation in intensity of observed fluorescence 

 from 1 mm. section transmitted through 

 different thicknesses of solution. 



Fluorescence corrected for absorption by 

 graphical method. Concentration = {. 



15 



10 



is one of these properties. If only the ions fluoresce the position of maxi- 

 mum fluorescence would evidently remain constant whether the material 

 of the solution were all ionized or not. 



This fixed position of maximum fluorescence is also consistent with the 

 theory suggested in Chapter I, 1 that fluo- 

 rescence is caused by an unusual kind of 

 dissociation similar to that produced in a gas 

 by the action of Roentgen rays. That part 

 of the solution which, during the process of 

 change, produces fluorescence does not give 

 evidence of any effect due to material not 

 dissociated beyond that of absorption. 



SUMMARY. 



The results of the above investigation upon 

 resorufin, as a typical fluorescent substance, 

 taken in connection with the work of B. 

 Walter and with the experiments described 

 in Chapter I, seem to establish the truth of 

 the following statements: 



1. Fluorescent solutions are optically 

 perfect substances,/, c, they obey Lambert's 

 law. 



2. Beer's law, i. c, that increase of concentration is equivalent to 

 increase in thickness, is true for dilute but not for concentrated solutions. 



3. A change in the concentration of a fluorescent solution has no effect 

 upon the typical fluorescence spectrum. 



'Nichols and Merritt, Physical Review, xix, No. 1, 1904; xxir, No. 5, 1906. 



0.55,/U 0.60JJ 



Fig. 37- 



0.6 5ju 



Fluorescence curves corrected for ab- 

 sorption by graphical method. Ver- 

 tical scale same as for Fig. 32. 



