144 



FLUORESCENCE OF THE URANYL SALTS. 



TABLE 53. Wave-lengths and frequencies of the broad-band series of the fluorescence of the 



sodium uranyl phosphates. 



form the usual constant-interval series. The interval, which is the 

 same for all within the errors of observation, is the shortest yet observed 

 in the study of the fluorescence of the uranyl salts. Position as well as 

 the arrangement of the bands is identical, and it is highly probable 

 that we have to do with the same 

 crystalline fluorescent compounds in 

 these three preparations. 



The broad bands of specimens 4 and 

 5 form series with a constant interval 

 of 82.5 units. Evidently the increase 

 in the proportion of phosphoric acid 

 tends to suppress the strongest line 

 series and merge the dimmer series 

 into broad bands. With the increas- 

 ing predominance of the broad bands, 

 caused by the increasingly larger pro- 

 portion of acid present, there is a si- 

 multaneous increase in interval from 

 82.5 units to 85.1 units for specimen 

 No. 6, and 87.0 units for specimen 

 No. 7. 



Experiments similar to the above 

 were made in which ammonium phos- 

 phate was substituted for sodium phos- 

 phate. The results were in all respects 

 analogous to those above described. 



That in general the resolution of the uranyl spectra by cooling occurs 

 only when the fluorescing substance is in crystalline form is further 

 substantiated by numerous experiments on frozen solutions to be 

 described in detail in Chapter X. 



