TABLE OF CONTENTS. 



PAGE 



Preface in 



Chapter. 



I. A Spectrophotometry Study of Fluorescence i 



Rhodamin and resorcin-blau 12 



Quinine sulphate 13 



Chlorophyll 17 



Canary glass 19 



Fluorite 20 



^Esculin 23 



Summary 24 



II. On the Absorbing Power and the Fluorescence of Resorufin. . . 25 



Historical 26 



Method of observation 27 



Composition of resorufin 27 



Absorption and thickness 28 



Absorption and concentration 32 



Fluorescence and concentration 33 



Summary 38 



III. The Luminescence of Sidot Blende 4 1 



Luminescence excited by Roentgen rays 41 



Photo-luminescence during excitation 42 



Failure of Stokes's law 45 



The phosphorescence spectrum during decay 45 



IV. The Decay of Phosphorescence in Sidot Blende and certain other 



SUBSTANCES 51 



Karly stages in the decay of phosphorescence in Sidot blende 53 



The study of phosphorescence in Sidot blende and certain other sub- 

 stances during the whole period of decay 58 



Experimental method 58 



Experiments with Sidot blende 59 



Experiments with different phosphorescent substances 67 



Summary 69 



V. The Influence of the Red and Infra-Red Rays upon the Photo- 

 luminescence of Sidot Blende 71 



Effect of the longer waves before excitation 71 



Influence of the longer waves during excitation 73 



Effect of the longer waves during decay 76 



Variations of the effect with the length of the longer waves 83 



VI. Variations in the Decay of Phosphorescence Produced by Heatino . . 85 



Experiments with Sidot blende 85 



Experiments with Balmain's paint 96 



VII. Studies of Phosphorescence of Short Duration 109 



Dr. Waggoner's studies in phosphorescence of short duration 109 



Methods of measurement 109 



Methods of preparing the phosphorescent compounds 110 



Discussion of results 114 



Effect of infra-red on the initial decay of Sidot blende 117 



Decay curves for different wave-lengths 118 



Spectrophotometry study of the cadmium-sodium compounds. ... 119 



Summary 121 



The experiments of Mr. Carl Zeller 121 



The aniline dyes 122 



The manganese-chloride group NaCl-MnCL 122 



The cadmium group 124 



Substances of slow decay 124 



v 



