122 



STUDIES IN LUMINESCENCE. 



reflected from the comparison lamp L. The color match was obtained 

 by using screens consisting of films stained with various aniline dyes on 

 glass. The lamp L was mounted on a photometer bar and could be moved 

 through a considerable range of distances. 



THE ANILINE DYES. 



The aniline dyes were dissolved in either zapon, gelatin, water glass, 

 or collodion, and flowed on glass. The glass proved to be too phos- 

 phorescent for its use; even oxidized brass emitted some light. Finally 

 black broad-cloth was used as a background, and the samples were tested 



in powdered form, the phospho- 

 roscope running at 2200 R.P.M. 

 From a lot of fifty samples ob- 

 tained from Heller and Merz, 

 the following show both fluores- 

 cence (F) and phosphorescence 

 (P) in slight degree : Naphthyl 

 carmine, white; F blue, P very 

 slight. Naphthyl sodium di- 

 sulphonate, gray; F blue, P 

 slight. Phthalic anhydride, 

 white; F light blue, P slight. 

 Naphthol sodium disulphonate, 

 gray; /''blue, P slight. Naphthol 

 sodium monsulphonate, gray; 

 F blue, P slight. Naphthol so- 

 dium sulphonate, gray; F blue, 

 P trace. Beta-naphthol, white; 

 F light blue, P trace. Tetra- 

 chlor phthalic anhydride, 

 white; F blue, P slight. Alpha 

 naphthylamine; F violet, P 

 slight. Nitro-naphthylamine, 

 light yellow; F green, P slight. 

 Sulphonate of soda, reddish; F blue, P slight. Several of these show 

 marked fluorescence when dissolved. Eosin, fluorescein, and rhodamin, in 

 powdered form, show no trace of phosphorescence. 



THE MANGANESE CHLORIDE GROUP NaCl-MnCl 2 . 



The substances had been prepared by Dr. Waggoner by mixing solutions 

 of MgClo and NaCl in known proportions and evaporating to dryness. 

 The percentage of MnCl^ varied in different cases from 0.0 1 per cent to 

 2.0 per cent. 



The samples were placed on brown cardboard with zapon varnish. The 

 phosphoroscope ran at 600 revolutions per minute, or one revolution in 

 o. 1 second. Time of excitation 0.025 second. The zero point was deter- 

 mined by readings taken at the point where reflected white light just 

 disappeared. In making a reading the mirror was turned just far enough 

 to shut off the direct reflected light. The standard was then moved until 



03 .04 



Seconds 



Fit 



129. 



Manganese-chloride group, ranging from 0.01 

 percentage concentration. 



to 20 



