126 



FLUORESCENCE OF THE URANYL SALTS. 



TABLE 41. Series in the absorption spectrum of uranyl nitrate hexahydrate 



fluorescence series F. There is some indication that several other 

 absorption series may be looked upon as associated with fluorescence 

 series in the same way. Thus the series a may perhaps be associated 

 with a very weak fluorescence series falling between D and E. Two 

 bands of such a series were occasionally observed at 1,968.0, and 

 2,053.4 (interval 85.4). The interval between the line at 2,053.4 and 

 the first line of series a is 70.6, which is almost exactly the average 

 interval for the absorption series. Again, in the case of series h we 

 might expect an absorption band to fall at 2,078.7, while series H might 

 have a fluorescence band at nearly the same point, viz, 2,079.3. Neither 

 band was observed; but it must be remembered that the detection of 

 reversible bands is only possible when the conditions of excitation are 

 suitable. Any trace of fluorescence tends to mask an absorption band, 

 and vice versa. The scarcity of bands, either of fluorescence or absorp- 

 tion, in the "reversal region" lying between 2,060 and 2,120 is perhaps 

 due to this cause. There are other cases which suggest the same rela- 

 tionship between fluorescence and absorption series, although less 

 definitely. 



While there are thus strong reasons for believing that certain fluores- 

 cence series are to be looked upon as associated, in the manner indi- 

 cated above, with absorption series, yet there are several series in the 

 fluorescence spectrum for which no related absorption series have been 

 observed; and, on the other hand, there are several absorption series 

 which do not appear to be related with the observed fluorescence. In 



