[cale] destruction OF FLUORESCENCE 263 



or absent, and complete transformation was brought about in six or 

 seven minutes. The decayed solution had a similar colour and 

 absorption spectrum (Plate IC) to the solution decayed by ultra- 

 violet light. 



The addition of a little acid to an aesculin solution caused the 

 destruction of the fluorescent substance. A few drops of hydroxide 

 restored the fluorescence of this liquid, but were unable to restore the 

 solutions transformed by ozone or ultraviolet light. 



An attempt will be made to ascertain whether the transformation 

 by ozone is a reaction similar to, or the same as, that brought about 

 by ultraviolet light. Although no definite conclusion can be deduced 

 it is felt that a more prolonged investigation in this direction should 

 be of interest and lead to fruitful results. 



Summary 



1. Measurements were made on the decrease of fluorescent 

 intensity on exposure to ultraviolet light. 



2. After the solution was once exposed it continued to decay 

 although kept in absolute darkness. 



3. On exposing to ultraviolet light the rate of decay decreased 

 very rapidly at first, then steadily. 



4. On recommencing the exposure after an interval of several 

 hours the rate of decay was more rapid than before the interval. 



5. Ozone caused a very rapid decay, producing a solution similar 

 to that transformed by ultraviolet light. 



This work was carried out under the direction of Professor J. C. 

 McLennan, to whom the writer wishes to express her sincere thanks 

 for his interest and helpful suggestions. 



Physical Laboratory, 

 University of Toronto. 

 May 15th, 1922. 



