54 



FLUORESCENCE OF THE URANYL SALTS. 



THE PHOSPHORESCENCE OF VARIOUS NITRATES. 



Observations were made on a series of nitrates previously prepared 

 for the detailed comparison of the fluorescence spectra of that salt. 1 

 These consist of crystals with 6 H 2 (rhombic), 3 H 2 O (triclinic), and 

 2 H 2 O (system undetermined) as water of crystallization and a speci- 

 men sealed in glass which had been rendered as nearly anhydrous as 

 was possible without decomposing the nitrate. 



The curves of decay indicate a much slower rate of decay for the 

 crystalline forms than for the anhydrous nitrate. Whatever effect the 

 amount of water of crystallization may have is doubtless masked by the 

 far greater influence of the crystalline form. This is perhaps to be 

 expected, since, as will be shown in Chapter VII, these specimens exhibit 

 as great differences in the structure and appearance of their fluores- 

 cence and absorption spectra as commonly exist between entirely 

 distinct uranyl salts. Similar differences in the case of salts similar in 

 composition but differing in crystalline form will likewise be described 

 in a subsequent chapter. 



FIG. 43. 

 OBSERVATIONS ON POLARIZED PHOSPHORESCENCE. 



Certain crystals of the double chlorides of uranyl exhibit fluorescence 

 spectra consisting of sets of bands polarized at right angles to one 

 another. To determine whether these components after the close of 

 excitation decay independently or without change in their relative 

 intensities, the following experiment was made : 



A crystal of the rubidium uranyl chloride that exhibited the phe- 

 nomenon of polarized fluorescence was mounted behind the disk of the 

 synchrono-phosphoroscope and was observed with a spectroscope. 



'Nichols and Howes; Physical Review (2), ix, p. 292. 1917. 



