THE NITRATES AND PHOSPHATES. 129 



of the bands are shown roughly in figure 78, where a typical group, 

 t. e., one band from each series, has been plotted for each of the salts 

 studied. 



TABLE 42. Series in the fluorescence spectrum ofuranyl nitrate trihydrate, UO^NO^t+SHiO. 



A. 1677.0, 1765.0, 1851.5, 1938.8, 2025.0, (2112.7, 2200.2). 



B. 1686.1, 1772.0, 1858.7, 1945.7, 2033.2, (2120.7). 



C. 1778.7, 1865.1, 1952.9, 2041.1, (2041.1). 



D. 1699.8, 1785.9, 1873.0, 1959.1, 2046.8, (2134.0, 2220.6, 2307.9). 



E. 1704.2, 1791.8, 1877.4, 1965.3, 2051.0. 



F. 1629.2, 1715.2, 1802.1, 1889.0, 1976.4, 2064.3? 



G. 1637.2, 1722.8, 1808.7, 1895.3, 1982.3, 2070.7. 



H. 1643.9, 1729.2, 1816.1, 1903.0, 1989.9, 2076.3, (2076.5, 2251.2). 



I. 1821.3, 1908.9. 1995.9, (2083.8). 



J. 1741.8, 1828.2, 1915.9, 2002.1, (2089.7). 



K. 1748.6, 1835.3, 1923.3, 2009.8. 



L. 1667.2, 1755.0, 1842.4, 1930.1, 2017.4, (2103.5, 2189.2, 2277.9). 



The second curve of figure 77, which shows the frequency of occur- 

 rence of the different possible intervals between the bands of the fluores- 

 cence spectrum, indicates a remarkably regular grouping of the bands. 

 Besides the principal interval 87 which is characteristic of the series in 

 this spectrum, a number of other intervals are almost equally promi- 

 nent, e. g., 7, 14, 30, 36, 43.5, 50, 80, 94. In the case of each of these 

 intervals the frequency of occurrence is far above the average. These 

 intervals, of course, correspond to the spacing of the bands in the 

 groups. Thus the interval 43.5, which is just half the principal interval 

 87.0, occurs twice in each group, the bands of series K lying half-way 

 between the bands of series F and the bands of series L half-way 

 between those of series G. In each case the two series might be com- 

 bined to form a single series with half the interval. Since, however, 

 the bands of the combined series would be alternately strong and weak, 

 it does not appear that such a combination is justified. 



In the absorption spectrum of the trihydrate, 48 bands were observed, 

 several of which, however, were so faint and indistinct as to make their 

 existence doubtful. As in the case of the hexahydrate, an interval 

 between bands of a little more than 70 is of frequent occurrence, and 

 37 of the bands (including all that are strong and well defined) can be 

 arranged in 9 constant-interval series. The interval does not appear 

 to be the same for all of these series, however. In one case the interval 

 is as high as 73.8, while in another case its value is 71.0. For most of 

 the series the interval lies near 72.0. 



In many instances the absorption series start with reversed fluores- 

 cence bands. Reversals are especially sharp and definite in the case of 

 the final bands of series C, G, H, and I (1/X = 2,041.1, 2,070.7, 2,076.3, 

 2,104.9). In other cases, the absorption series begins at a point where 

 a fluorescence band might be expected, but where none was actually 

 observed. Thus, we should expect the final bands of series I, J, and K 

 to lie at 2,082.7, 2,009.0, and2,096.6 respectively. These bands were not 

 observed, probably because of the fact that the three series in question 



