120 



STUDIES IN LUMINESCENCE. 



manganese-sulphate preparation previously observed, which showed a 

 band extending from 0.514 to 0.623 n, with a maximum at 0.565 /j.. It 

 would seem from these results that the manganese salts produce, when 

 added to a cadmium salt, a phosphorescent compound whose spectrum 

 shows the same maximum, and is independent of the salt. 



B 



,\>H 



Ct W 



Fig. 124. 

 Showing top view of phosphoroscope. 



50 5^ 58 62 



Fig. 126. 



Showing the phosphorescence spectrum of 

 a CdS04-MnCl-2 compound, taken 1.44 

 seconds after excitation. 



Of the sodium salts this is not true, for the colors are widely different. 

 An attempt was made to measure the spectrum of all the sodium compounds, 

 but'in most cases the intensity was far too small to measure. 



52 



54 



56 



58 



60 



62 



Fig. 125. 



Showing the phosphorescence spectrum of a Cd-Na2- 

 Mn04 compound, taken 0.374 second after excitation. 



12 3 4- 



Seconds 

 Fig. 127. 



Showing curve of decay of a CdSOj-NaBr 

 compound. 



Decay curves were taken from all the compounds whose intensity was 

 sufficient to measure. All these curves show the same characteristics when 

 plotted with the reciprocal of the square root of the intensity as ordinates 



