106 FLUORESCENCE OF THE URANYL SALTS. 



The uranyl ammonium chloride group shows a strong similarity to 

 the preceding group. All except band B appear as polarized doublets. 

 Components D w and A w were discerned only with the greatest diffi- 

 culty. 



The uranyl rubidium chloride group is very similar to the uranyl 

 potassium chloride group. Band B g is missing, but as in the potassium 

 chloride, there is a 185 component to the red of B w . Component 

 C w has a position nearer D g than has C w in the preceding spectra. 

 This is also the condition existing in the caesium-chloride spectrum, 

 and it is possible, since no D w component is visible in either spectrum, 

 that D w is very dim, and hidden in C w . 



Uranyl caesium chloride gives the most satisfactory set of fluores- 

 cence bands, since both components of band B are present, and the 

 C, E, and A components are very well separated. It is interesting to 

 note that B g is of longer wave-length than B w , as is the 185 com- 

 ponent of B g in the preceding salts. 



It has been previously stated that the absorption spectra, like the 

 fluorescence spectra, are composed of series, which begin with the 

 bands which terminate the fluorescence series. The absorption bands 

 which lie nearest the fluorescence region can also be arranged in recur- 

 ring groups. The absorption series will be designated 6, c, d, e, a; 

 since they join the B, C, D, E, and A fluorescence series, respectively. 

 The e and A series are the strongest in the reversing region, but grad- 

 ually vanish, while the D series becomes stronger toward the ultra- 

 violet. Figure 72 gives a typical absorption group for each of the four 

 salts. As before, the components above the line belong to the green ; 

 those below to the white polarization. 



By comparing the uranyl potassium chloride absorption group in 

 figure 72 with the fluorescence group of the same salt in figure 71, it 

 will be seen that there is no b g component present, as there was no 

 B g component present, but that c g) d g , e g , and a g , corresponding to 

 series C g , D g , E g , and A g are present and that there are no other series 

 represented. Although the relative intensities of the absorption com- 

 ponents are almost reversed when compared with the relative intensi- 

 ties of the fluorescence bands, the same spacing exists between the 

 green components of both fluorescence and absorption. In the white 

 polarization group, c w corresponds, in position, to C w , and e w to 

 E w , while b w a w serves both B w and A w series in the following way: B w 

 is the first member of each fluorescence group, while A w is the band 

 of the preceding group which is nearest to B w . As the fluoresence 

 intervals of both the A and B series are approximately 83 frequency 

 units, and A w is 12 units distant from B w , the reversing band of the a w 

 series must coincide with the second member of the b w absorption 

 series, since it is 71 units from the reversing band B w or b w . The d w 

 component is absent, as is D w , and there are no superfluous series. 



