THE NITRATES AND PHOSPHATES. 



139 



That the crystal system to which a salt belongs is an important factor 

 in determining the position of the bands can be seen in figure 80. In 

 the left-hand panel a single group is shown in its natural position; in 

 the right-hand panel the strongest bands of each group are placed in 

 the same vertical line, to show the resemblance in grouping. This 

 similarity is probably due to the fact that all four belong to the same 

 chemical family. If we compare this grouping with that of the uranyl 

 nitrate spectra in section i we find little resemblance, hence the 

 grouping is probably characteristic of the double uranyl-nitrate family. 

 In the left-hand panel it will be seen that the second and fourth groups 

 occupy almost identical positions, while the first and third occupy 

 positions which differ from one another and from the second or fourth. 

 As has previously been stated, the second and fourth groups belong 



TABLE 49. Series of the fluorescence spectrum of di-potassium uranyl nitrate. 



