196 



FLUORESCENCE OF THE URANYL SALTS. 



able. With falling temperature these increased in brightness and two 

 more bands came up to the threshold of vision. Bands 0.4890 at 

 corresponds with an absorption band at 0.4870 discovered by Jones 

 and Strong. The crystalline nitrate, with 6 H 2 O, also has an absorp- 

 tion band at 0.4870. 



While continuing the cooling process at a slow rate, a sharp rise in 

 temperature from 25 to 18 was invariably noticed, probably 

 due to undercooling or change in hydration. Immediately following 

 this stage portions of the background increased greatly in brightness 

 so as to broaden each band on the violet side. These very broad bands, 

 which exist at temperatures between 25 and 40, were found on 

 subsequent cooling to be the parents of groups of resolved bands. The 

 40 bands were five times the intensity of the +20 bands. 



TABLE 118. Uranyl nitrate in water normal solution. 



At 46 the portion of each band toward the violet decreased in 

 intensity as the part of longer wave-length became stronger, thereby 

 tending to both narrow the band and produce a decided crest. It was 

 found, with the aid of the spectro-photometer, that the intensity of the 

 stronger crest at 60 was 85 times that of the homologous band at 

 +20. 



Further cooling resolved the stronger band into doublets without a 

 real shift, but the dimmer component was not so easily resolved. At 

 temperatures between 120 and 180 the strongly resolved doublets 

 formed two series, both of a constant frequency interval of 88 units, 

 the single band at 0.4885 being a member of one series. There was 



