Fluorescence of Dyes on Wave-Length of Exciting Light. 317 



The intensity of fluorescence for every dye is measured 

 with 8 to 10 light-filters with a constant thickness of absorbing 

 layer d. For Fluorescein and Eosin two measurements were 

 made with different d. Every measurement was repeated 

 at least three times on different days. 



For ascertaining the amount of diffused light in the mea- 

 sured light of fluorescence, the solution of dye in the vessel 

 F was replaced by pure water. In all cases the quantity of 

 the diffused light was not more than 1 per cent. : i.e., could 

 be disregarded. 



Results. 



We abstain from the reproduction of lengthy tables with 

 elements necessary for graphical calculations of <I> on the 

 basis of (8). The values of I A , xc y e~ xcd \ f(X) were taken 

 from experimental curves for every 5 fjbfj,. As an example 

 of the subintegral function so obtained we include fig. 4, 

 representing nine curves obtained for Eosin with different 

 light-filters. Beside every curve is given the value of <J>, 

 obtained by a graphical integration in the relative units, the 

 observed value of intensity of fluorescence, also in relative 

 units, and the relation 



4> 



As shown in the figure, the curves are approximately 

 symmetrical. According to the above mentioued, we can con- 

 sider that k so computed corresponds more or less to the wave- 

 length through which passes the halving ordinate of area <I>. 

 On every curve this ordinate is marked by a dotted line. 

 The Tables IF, III., IV. contain the following data : — 

 (1) light-filter used, (2) the value of A, through which 

 passes the halving ordinate, (3) F, (4) <f>, (5) k. The tables 

 give also d and concentration. The tables correspond to the 

 most careful measurements. 



Table II. 



Fluorescein. c = '3'7 . 10~ 6 - gr -, ; d^O'SO. 



cm.- 5 



X. F. 0. K . 



5 446 ft/* 2-940 61-0 4-81.10-2 



14 448 00579 123 4'70 



13 449 0-920 19'3 4-77 



10 453 370 7-50 4-93 



482 14-60 296 4-88 



7 506 362 7-45 4"86 



8 510 4-90 97-0 5'05 



3 ... . 519 0-218 4-55 4*80 



