ABSORPTION AND EMISSION CENTERS. 7 



Weigert believes that there are formed molecular complexes or "reaction 

 nuclei" by the light, analogous to the ions formed by ultra-violet light in air; 

 and these "reaction nuclei" play the role of a catalyzer, the reaction being 

 produced with very great velocity on the surfaces of these nuclei, and the speed 

 of the reaction will then be a function of the rate of diffusion of these nuclei. 



Weigert finds that these "reaction nuclei" act as nuclei for the conden- 

 sation, and thus supports the views of Burgess and Chapman. 1 When the 

 light has produced a number of the "reaction nuclei," it is found that the 

 number of these decay like ordinary ions. The "reaction nuclei" also accel- 

 erate the following reactions: 



(1) Dissociation of oxychloride of carbon. 



(2) Oxidization of hydrogen. 



(3) Oxidization of sulphurous acid. 



(4) Decomposition of ozone. 



(5) Oxidization of hydrochloric acid gas. 



(6) Formation of ammonia. 



EMISSION SPECTRA OF ORGANIC COMPOUNDS. 



Goldstein 2 has shown that bright, fluorescent, and phosphorescent light 

 is emitted by solid aromatic compounds. The stimulation is best produced by 

 cathode-ray bombardment. To prevent the evaporation of the compounds, 

 they are kept cooled by liquid air. Goldstein has investigated a large number 

 of organic compounds such as benzene, the three xylenes, benzonitrile, the 

 quinolines, acetophenone, etc. In many cases three spectra appear which 

 Goldstein calls the initial, the chief, and the solution spectra. 



During the first moments of excitation the initial emission spectrum is 

 quite strong, but it soon becomes very weak without disappearing. At the 

 same time that the initial spectrum begins to diminish in intensity the chief 

 spectrum appears. This spectrum is a very characteristic one, even for iso- 

 meric compounds. The third type of spectra only appears when an aromatic 

 compound is dissolved in a liquid and the solidified solution is exposed to 

 cathode rays. 



The chief spectrum consists largely of narrow channeled bands, which 

 usually have their sharper edges on the short wave-length side. These spectra 

 never have bands of shorter wave-length than X 4600. The initial spectra 

 extend much farther than this into the region of short waves. 



Chief Spectrum of Naphthalene. 



/ 5390 (very bright) 5890 (very bright) 



5550 6150 (probably double) 



5600 6300 



5730 6480 



Spectrum of Naphthalene in Monochlorbenzene. 



3. 4730 bright 5050 5170 faint 5400 faint 5570 faint 5820 faint 



4830 " 5100 5230 " 5450 " 5650 " 



The solution spectrum varies greatly for different solvents, even for 

 isomeric compounds. 



1 Trans. Chem. Soc, 89, 1423 (1906). 



2 Verhandl. d. deutsch. Ges., vi, 156, 185 (1904); Phil. Mag., 20, 619 (1910). 



