184 



FLUORESCENCE OF THE URANYL SALTS. 



Jones and Strong discovered a shift of 15 A.u. toward the red for 

 the absorption band of wave-length 0.4910 when the temperature of 

 their solution was raised from +5 to +84. Our fluorescence band 

 at 0.4927 shifts in the same direction, with a rise in temperature from 

 -90 to +20. 



H. Becquerel believed that any modification of the absorption 

 spectrum is accompanied by a similar change in the fluorescence spec- 

 trum, and these shifts lend strength to his generalization. 



A brief study of the fluorescence spectra of the 1/10 and the 1/100 

 normal solutions at different temperatures indicates that a similar 

 temperature shift occurs. 



60 



-120 



J L 



J L 



30 70 



J L 



40 



no TO BO TO BO /u ow *" "* w 



FIG. 91. Uranyl sulphate Temperature shift. 



(1) 1/1 normal, aqueous: (2) 1/10 normal, aqueous: (3) 1/100 normal, aqueoua; (4) 40 c.o. 1/10 normal, 

 aqueous to 1 c.c. sulphuric acid; (5) 1 c.c. 1/10 normal, aqueous to 1 c.c. sulphuric acid. 



The increase in the amount of solvent produces a shift of the spec- 

 trum toward the violet. For example, band 7 at 90 shifts as fol- 

 lows: in the 1/1 normal solution the wave-length is 0.4919, in the 1/10 

 normal 04910, in the 1/100 normal 0.4907, in the 1/1000 normal 

 0.4904 M. 



The 1/1000 normal solution shows a spectrum which is very strongly 

 shifted toward the violet The above comparison of the wave-lengths 

 of band 7 fails to indicate the shift of the spectrum, because it is accom- 

 panied by a marked decrease in interval, while of all the bands, number 

 7 is the least shifted. For example, band 4 of the 1/1000 normal at a 

 temperature of 90 is of wave-length 0.5583, while band 4 of the 

 1/100 normal at 90 is of wave-length 0.5631 units. Bands 5, 6, and 

 7 show progressively less variance in wave-length with the correspond- 

 ing bands of the 1/100 normal solution because of the shorter frequency 

 of the 1/1000 normal interval. Measurements of these spectra plotted 

 on a frequency scale indicate that while the bands are spaced by about 

 85.7 units in the 1/1, 1/10, and 1/100 normal solutions, the 1/1000 



