THE NITRATES AND PHOSPHATES. 131 



are given in table 44, and a typical group, consisting of one band from 

 each series, is shown in figure 78. Many of the bands that do not fall 

 into these 12 series nevertheless seem to belong to similar series of 

 which only 2 or 3 bands could be detected. Two of these suspected 

 series have been included in figure 78, where they are indicated by 

 dotted lines. 



TABLE 44. Series in the fluorescence spectrum ofuranyl nitrate dihydrate [U0 2 (N03)i+2HzO]. 



A. 1676.7 1765.9 1853.0 1942.7 2030.7 



B. 1684.9 1773.7 1861.6 1951.0 2037.9 



J. 1645.3 1734.6 1821.2 1909.0 1998.4 



K. 1830.5 1918.3. 



L. 1658.4 1745.5 1834.9 1923.8 2009.3 (2095.9) 



M. 1751.0 1838.2 1926.8 2015.5 (2102.7 2191.3 2278.0) 



The absorption bands were located by observing the spectrum of 

 light from a continuous source after diffuse reflection from a mass of 

 small crystals. Although the bands observed in this way are sur- 

 prisingly sharp, the method is not so satisfactory as that in which the 

 light is analyzed after direct transmission through a single crystal. 

 It is doubtful whether the reflection method gives as great accuracy 

 in the location of the bands, and many of the weaker bands, which 

 would have been easily detected if large crystals had been available, 

 were probably not observed at all. For this reason, perhaps, the 

 absorption spectrum of the dihydrate shows only four well-defined 

 series. The reciprocal wave-lengths for these series are given in table 

 45. The interval between bands is 70.0 for series ra, 70.4 for series j, 

 and 71.3 for series g and h. In each case the first band in the absorp- 

 tion series occupies nearly the same position as the last band in one 

 of the fluorescence series. 



TABLE 45. Series in the absorption spectrum of uranyl nitrate dihydrate 



2362.9 



THE ANHYDROUS NITRATE. 



Specimens of uranyl nitrate that were in all likelihood anhydrjus, 

 and which certainly contained less water than the dihydrate, were 

 prepared by allowing nitric anhydride, N 2 O 2 , to react with uranic oxide. 

 The nitric anhydride was distilled from a mixture of nitric acid and 

 phosphorus pentoxide, while the uranic oxide was prepared by heating 

 uranic acid, H 2 UO 4 . In preparing the oxide, the heating was not con- 

 tinued so long as to completely drive off the water from the uranic 



