THE NITRATES AND PHOSPHATES. 



135 



possible the absorption spectrum was obtained by transmitted light. 

 The crystals from an acid solution were of a deeper green color than 

 those from a water solution, which necessitated grinding to about 

 0.4 mm. thickness to make them sufficiently transparent. Since the 

 immersion in liquid air spoiled a crystal, many crystals of each form 

 had to be prepared. 



Since, as is usual with the uranyl salts, we have in these spectra series 

 of constant-frequency intervals, the location of the bands (tables 

 46, 47, 48, 49) is indicated in frequency units. As elsewhere in 

 this treatise, fluorescence series are denoted by capital letters (A, B, 

 C, etc.) and the related absorption series by a, 6, c, etc., or where the 

 relation is not obvious, by Greek letters. 



The four spectra are mapped in the usual manner in figure 79. 



Fio. 79. 1. Fluorescence and absorption spectra of mono-ammonium uranyl nitrate, NH^UO 

 (N03)s. 2. Diammonium uranyl nitrate, (NEU^UC^CNOa^^HaO. 3. Mono-potassium 

 uranyl nitrate, KUCMNOs^- 4. Di-potassium uranyl nitrate, 



In the spectra of these double nitrates, the relation of absorption to 

 fluorescence is somewhat simpler than is the case with the uranyl 

 nitrates described in section i of this chapter, but it is less systematic 

 and complete than in the spectra of the double chlorides. Thus, in 

 mono-ammonium and mono-potassium salts (table 46 and 48), there are 

 not sufficient absorption series to match all the fluorescence series, 

 but there are no absorption series that do not join. In the di-ammonium 

 spectrum (table 47) there is a related absorption series for each fluores- 

 cence series and three extra absorption series that are not obviously 

 related to fluorescence. (See plate 1,6.) In the spectrum of the di-potas- 

 sium salt, fluorescence series B, D, G, I, and J have no corresponding 

 absorption of measurable intensity, while there are two absorption 

 series, I' and g, apparently with a direct reversing linkage with the 

 fluorescence. As to the completeness of classification of bands, it can 



