THE SULPHATES. 



175 



TABLE 104. Uranyl ccesium sulphate: Cs-zUO^SO^ 2HiO. Fluorescence at 185 C. 



Prepared by precipitating uranyl sulphate by adding caesium sulphate in calculated amount to 

 form the double salt, which is very insoluble. The composition of the crystals is given as above 

 by O. de Coninck (Chem. Centralblat, ix, 1, 1306, 1095). The preparation consisted of very 

 small square plates about 0.01 mm. on a side, the largest of which showed an apparently uniaxial 

 negative figure. The crystals are therefore presumably tetragonal. 



FREQUENCY INTERVALS OF THE FLUORESCENCE SERIES. 



The average frequency intervals of the various series, as derived 

 from the foregoing tables, are given in table 105, together with the 

 weighted average for each salt. It will be noted that the intervals of 

 the single sulphate and the double salt of caesium are distinctly greater 

 than the intervals of the other four sulphates. There is nothing 

 fortuitous about these differences, for, as will be seen from the table, 

 the different series for each salt have intervals within one frequency 

 unit of the general average for that salt, with three exceptions. 



These exceptions are series Ci in the ammonium and sodium double 

 sulphates and GI in the ammonium salt. Such occasional apparent 

 discrepancies are not uncommon in the fluorescence spectra of the 

 uranyl salts. They are not due to accidental errors, but are probably 

 ascribable to the complexity of bands having overlapping components 

 the relative intensity of which in different portions of the spectrum 

 varies progressively. Many such cases are known. A doublet ill- 

 resolved and appearing as a single hazy band, the component of longer 



