VI CONTENTS. 



Chapter. page 



VIII. Photographic Studies of Luminescence 125 



The distribution of energy in the fluorescence spectrum and the 



phosphorescence spectrum of Sidot blende 125 



Phosphorescence at room temperature 128 



Discussion of method 129 



The phosphorescence spectrum during decay and the question of 



two overlapping bands 131 



Experimental 132 



A photographic test of the effect of infra-red rays 134 



The effect of temperature on the fluorescence spectrum 135 



Discussion of results 136 



IX. A Spectrophotometry Study of Certain Cases of Kathodo-Lumi- 



nescence 137 



Willemite 1 40 



Sidot blende 141 



Dependence of kathodo-luminescence upon current and discharge 



potential 143 



Conclusions 1 44 



X. On the Electrical Properties of Fluorescent Solutions and Vapors 147 



The influence of fluorescence upon electrical conductivity 147 



Photo-active cells with fluorescent electrolytes (Dr. Hodge's experi- 

 ments) 152 



Mr. Howe's experiments on fluorescent anthracene vapor 163 



Apparatus 164 



Observations and results 165 



Conclusions 166 



XI. On Fluorescence Absorption 167 



XII. The Distribution of Energy in Fluorescence Spectra 175 



Determination of the distribution of energy in the spectrum of the 



comparison flame 175 



Comparison of the fluorescence spectra with the spectrum of the 



standard acetylene flame 179 



The correction for slit width 182 



The correction for absorption 1 85 



The energy curves of fluorescence 186 



XIII. The Specific Exciting Power of the Different Wave-lengths of 



the Visible Spectrum in the Case of the Fluorescence of 



eosin and resorufin 1 87 



Coefficients of absorption 1 89 



Computation of specific exciting power 191 



XIV. The Theory of Wiedemann and Schmidt 195 



XV. The Phenomena of Phosphorescence Considered from the Stand- 

 point of the Dissociation Theory 201 



Summary of experimental laws 201 



The decay of phosphorescence under simple conditions 202 



Absorption effects 205 



Influence of irregularities in distribution of the active material 208 



Diffusion effects 211 



Influence of ionic grouping 212 



Hysteresis, temperature effects, etc., explained by ionic grouping. . 218 



Summary 222 



Index -?-'4 



