142 



FLUORESCENCE OF THE URANYL SALTS. 



Not all uranyl fluorescence spectra are well resolved on cooling. In 

 the case of a piece of canary glass, for example, the rather unusually 

 broad, vague doublet occurs at +20 (see table 51) . 



At the temperature of liquid air the doublet is partially resolved, 

 but no narrow components appear. 



The solid solution of uranyl phosphate in microcosmic salt, the 

 phosphorescence of which has already been described in Chapter IV, 

 yields a narrowing of the bands on cooling and a shift, but no resolution. 

 (See table 52.) 



TABLE 52. Bands of uranyl phosphate in microcosmic salt. 1 



1 The bands are 160 A. u. in width. 



The inference that the failure to obtain resolution of the bands is 

 due to the non-crystalline structure of the substance is confirmed by 

 the observations described below. 



EXPERIMENTS ON THE SPECTRA OF SODIUM URANYL PHOSPHATES. 1 



Stokes, 2 in an early paper on the ultra-violet spark spectra of the 

 metals, described a fluorescent screen prepared by treating the ordi- 

 nary uranyl phosphate with a solution of phosphoric acid and sodium 

 or ammonium phosphate. While the uranyl phosphate is only feebly 

 fluorescent, the double salts thus produced were very brilliant. 



To investigate the fluorescence spectra of these double phosphates, 

 the following preparations were made : 



(1) A mixture of uranyl phosphate and sodium phosphate in the ratio of 

 4 molecular weights of HU0 2 P0 4 .3|H 2 to 1 molecular weight of HUo 2 P0 4 . 



(2) A similar mixture in proportions 2 to 1. 



(3) A similar mixture in proportions 1 to 1. 



These three specimens, when cooled to 180 C. and excited by 

 radiation from the carbon arc, yielded precisely similar and well- 

 resolved spectra. (See fig. 81, 1, 2, and 8.} 



In addition to the above, four further specimens were made by 

 mixing increasing amounts of phosphoric acid with sodium uranyl 

 phosphate, i. e.: 



(4) One molecule of phosphoric acid to 2 molecules of uranyl phosphate 

 and 1 molecule of sodium phosphate, giving the composition H 3 NaUO 2 (P0 4 ) 2 

 This was a powder, similar to preparations 1, 2, and 3. 



1 Howes and Wilber, Physical Review (2), vn, p. 394. 1916. 



2 Stokes, Philos. Trans., 152, p. 599. 1862. 



