A SPECTROPHOTOMETRY STUDY OF FEUORESCENCK. 



^3 



sharply as is the case of the white fiuorite. The broadening of the band 

 upon this side may result in a slight shifting of the fluorescence. It has 

 already been shown by Stenger 1 and by O. Knoblauch 2 that fluorescent 

 substances such as eosin and naphthalin-roth have the position of the fluo- 

 rescent spectrum shifted by dissolving them in different liquids; and that 

 the shift corresponds with that of the absorption band previously described 

 by Kundt. 3 



^SCULIN. 



This substance was cited by L,ommel 4 as typical of his second class, 

 the characteristics of which are a fluorescence spectrum independent of 

 the wave-length of the exciting source and an absorption band beginning 

 at that point in the spectrum at which the first trace of fluorescence shows 



Fig. 2i. -Esculin (from horse chestnut). 



Curve A. Fluorescence spectrum when excited by arc light. 

 Curve T. Transmission spectrum of a layer 8 cm. thick. 



itself and extending toward the violet, so that there is no overlapping of 

 the band of the exciting light with the fluorescence spectrum. 



Our measurements of the fluorescence of sesculin were made upon a 

 solution consisting of water in which freshly broken twigs of the horse- 

 chestnut tree had been immersed. When freshly prepared this shows the 

 well-known fluorescence characteristic of aesculin, but the solution loses 

 its activity upon standing. We were unable to procure pure aesculin, but 

 the results, so far as the form and composition of the fluorescence curve 

 are concerned, would probably be the same had measurements been made 

 upon the solution of the chemically prepared substance. The fluorescence 

 curve, Fig. 21, is of the usual form and its position with reference to the 



Stenger, Wied. Ann., 28, p. 201. 



j O. Knoblauch, Wied. Ann., 54, p. 193. 



3 Kundt, Wied. Ann., 4, p. 34, 1878. 

 *Lommel, Poggendorff's Ann., 143, p. 38. 



