3 



STUDIES IN LUMINESCENCE. 



-' 



As a further check the positions of alcohol and resorufin were reversed, the 

 alcohol being placed in front of D and the resorufin in front of C. Then 



D =J J_ Co 



C*2 /o Cl 



It will be noticed that in this method also the disturbances due to reflec- 

 tion from the surfaces of the cells are eliminated. 



From these data the value of the coefficient of absorption for each wave- 

 length was found to be practically the same as that found b) r the first 



0.4 



0.4// 0.5// 0.6// 



x= points for cell 1.075 cm. tnick 

 = 2.05 " 



0.7// 



Fig. 26. 



Coefficient of absorption as computed from cells of different thickness. 



method and independent of the thickness of the cell. Absorption curves 

 plotted from average values obtained by both methods, using cells of two 

 thicknesses, are identical, as shown in Fig. 26. l The absorption coefficients 

 for different concentrations and also the data from which the computation 

 was made are given in Table 3. 



Table 3. 



Coefficient of absorption computed from cells of different thickness. Concentration 

 = 1/16. 7 = Intensity of light before transmission. /= Intensity of light after 

 transmission. /3 = Coefficient of absorption. 



'Figures 26, 27, and 28 give only relative values of coefficients, since they are drawn from data computed 

 upon the basis of ordinary instead of natural logarithms. To get from the curves the absolute value of 

 the coefficients given in the tables multiply by 2.3. 



2 These values are average results from a number of observations. 



