THE NITRATES AND PHOSPHATES. 145 



SUMMARY OF SECTION III. 



(1) Where uranyl compounds occur in solid solution, as in canary 

 glass, or in a bead of microcosmic salt, the banded fluorescence spec- 

 trum with constant frequency intervals, as observed at +20 C., is 

 not further resolved into groups of narrow, line-like bands by cooling 

 to the temperature of liquid air. 



(2) Sodium uranyl phosphate or ammonium uranyl phosphate, 

 when prepared in the form of crystalline powder, gives fluorescence 

 spectra which are fully resolved at low temperatures. 



(3) In the presence of an excess of phosphoric acid, where the 

 above compounds, or uranyl phosphate, form solid solutions of vitreous 

 structure, resolution does not occur on cooling. 



(4) There is reason to think that the dependence of resolution by 

 cooling upon the existence of crystalline structure applies in general 

 to the fluorescence of the uranyl salts. 



