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LXIV. On Threefold Emission-Spectra of Solid Aromatic 

 Compounds, By Professor E. Goldstein *. 



SOME years ago I observed f that bright, fluorescent, and 

 phosphorescent light is emitted by a number of aromatic 

 solid compounds — for example, naphthalene, xanthone, anthra- 

 cene, &c. — if cathode rays strike on these substances, cooled by 

 liquid air to prevent their evaporation and decomposition. 

 In this way I was also able to obtain bright-light emission 

 from a great many substances, which at an ordinary tem- 

 perature are liquid bodies — for example, benzene, the three 

 xylenes, benzonitrile, the chinolines, acetophenone, &c. The 

 light emitted by these substances gave bright discontinuous 

 spectra of a great variety, all consisting of bands of various 

 width and intensity. 



Since that time I have extended this research on nearly 

 all aromatic substances which I could obtain in any way, and 

 have thus obtained about two thousand emission-spectra of 

 aromatic substances and of mixtures of such substances with 

 other bodies. 



Of course, time does not allow me to give a complete 

 report of this work. Here I just want to speak about one 

 result of my experiments. 



In the beginning I was satisfied to observe just a single 

 spectrum for each substance, because it was thought that 

 every substance could emit only one single spectrum. But 

 soon I found that the complexity of phenomena is much 

 greater than it seemed at first sight. For each substance 

 does not show only one spectrum, but, according to the condi- 

 tions of the experiment, there may appear three spectra, which 

 are quite different from each other, and have no coincident 

 maximum. I call these three kinds of spectra respectively 

 the initial-spectrum, the chief-spectrum, and the solution- 

 spectrum of the substance. 



At the first moment, when cathode-rays fall upon the sub- 

 stances, there appears quite alone and bright the spectrum 

 which I call the initial-spectrum. Then the brightness of the 

 initial-spectrum diminishes and gets fainter and fainter till 

 its density becomes very small; but it never entirely disappears. 

 When the initial-spectrum gets fainter, the chief-spectrum at 

 the same time appears and grows brighter and brighter. 



* Communicated by the Author. Read at the Winnipeg Meeting of 

 the British Association, August 1909. 



t Verhandl, d. Deutsch. Physik. Ges., vi. p. 156, and vi. p. 185 

 (1904). 



