12 



FLUORESCENCE OF THE URANYL SALTS. 



bands. There are at least 7 such bands, 4 of which are seen in the 

 spectroscope with a region in the violet not readily resolved by visual 

 observations. This violet fluorescence has, however, been determined 

 photographically by Miss McDowell. 1 The approximate location of 

 the bands in this spectrum is shown in figure 4. 



TABLE 2. Approximate wave-lengths and frequencies of visible crests in the spectrum of a 

 phosphorescent barium sulphide (Ba; Cu; Na 2 B 4 O7). 



While all of these bands are pressnt in the fluorescence of the impure 

 commercial product, they are not all due to any one constituent. By 

 solution and subsequent fractional sublimation, as is well known, it 

 is possible to partially separate the substance into pure anthracene, 

 which has a violet fluorescence and a residue containing chrysogen, the 

 fluorescence of which is green. 



1600 



1800 2000 



I I I I 



I 22 . 



FIG. 4. 



Miss McDowell has shown that the bands 6, 7, and 8 belong to the 

 anthracene thus obtained, while band 4 is also present in its spectrum. 

 Bands 1, 2, 3, and 4 are characteristic of the green residue. 



1 Miss L. S. McDowell, Physical Review (1), xxvi, p. 155. 1908. 



