150 



FLUORESCENCE OF THE URANYL SALTS. 



The double acetates of sodium, magnesium, zinc, silver, and lead 

 (fig. 84, a) are made up of groups which, while they overlap, are by no 

 means identical, either as to the location or arrangement of their bands. 



The spectra of these 5 salts agree, however, in this: They contain 

 in each group 5 bands which correspond so closely with the bands 

 B, C, D, E, and F of the double acetates depicted in figure 83 that by 

 a bodily shift of the group as a whole they may be made to conform 

 to the uniform arrangement, so far as those bands are concerned, quite 

 as well as do the latter. This may be seen from figure 84 6, in which 

 the dotted vertical lines indicate the positions of the bands in the uni- 

 form type, while the group in each case has been shifted so as to 

 register approximately. 



DOUBLE ACETATCS 



FIG. 84a. 



FIG. 846. 



The distinction between the spectra under discussion and those 

 previously considered, which were described as having group spectra 

 conforming to an essentially uniform type both as to location of bands 

 and group-structure, is twofold : (a) there is a shift of the groups as a 

 whole; (6) there are additional series, varying in intensity, some of 

 which are among the strongest in the spectra and which are charac- 

 teristic of the individual salt. 



It should be reiterated in this connection that neither the bands 

 B, C, D, E, and F, which, although sometimes uniformly shifted, are 

 common to the spectra of the double acetates, nor the additional 

 bands, are found in the spectra of the single acetates. The spectrum 

 of neither the anhydrous acetate nor the crystalline form can be made 

 to conform to the uniform type by a general shift. 



