114 The Ohio Journal of Science [Vol. XVI, No. 4, 



In 1S97 A. C. Jones published an article (Ann. der Phy. 

 N. E. Vol. ()2, page 31) in which he confirmed the results 

 obtained by Peirce and extended the investigations on the 

 bands into the ultraviolet region. 



The latest research on the subject is by A. H. Chapman 

 (Physical Review, Second Series, Vol. IV, 1914), who used 

 mercuric iodide, ferric iodide and stannic iodide. In a gen- 

 eralized conclusion he says "that a wide emission band 

 shading off towards the violet and the red is characteristic 

 of the compounds investigated, and that when the absorption 

 spectrum of the compound is available, there seems to be a 

 definite relation existing between the absorption and emission 

 bands. It would seem therefore that the vibrating system 

 responsible for the emission is also effective in producing 

 absorption in solution." 



It is the purpose of the investigations here reported upon 

 to extend our present knowledge of the emission spectra of 

 compounds and to determine, if possible, something concerning 

 the nature and structure of the vibrating system or systems 

 responsible for the spectra. It was also hoped to make some 

 comparisons between the emission and absorption spectra 

 of the vapors with certain of the compounds used, but in this 

 latter proposition little success has come. There have arisen, 

 however, in connection with these latter investigations some 

 very interesting phenomena which have either thrown some 

 light on the main problem in hand or furnished a basis for 

 some suggestions as to the nature of the thermions from heated 

 salts. 



APPARATUS. 



The upper electrode of the apparatus used for examining 

 emission spectra was a brass tube about seven-eights inch in 

 diameter and three inches long, the lower one being a brass 

 tube about three-quarters inch in diameter and eight inches 

 long, with one end tightly sealed with a brass plug. A water 

 cooling jacket was constructed around the upper end of the 

 lower electrode; this served as a screen to prevent direct contact 

 of the gas flame with the rest of the apparatus and, operating 

 as a cooler, preserved the waxed joints and corks. The two 

 metal tubes were connected by a piece of heavy capillary 

 tubing of about 1.3 mm. inside bore. Capillary tubes of 



