Absorption Spectra ofUranous and Uranyl Compounds. 567 



that we tried. Uranous sulphate and uranous acetate are not 

 as stable as the chloride but may be kept in most solvents. 

 Uranous nitrate is very unstable and no photographic work 

 could be done upon its absorption spectra. When nitric acid 

 is added to a solution of uranous acetate the salt is changed 

 into a yellow uranyl salt. Photographs have been taken of 

 the absorption spectra at the various stages of these changes. 

 A spectroscope with a Rowland grating was used, and the 

 method of work is that described by Jones and Strong *. 



The uranyl absorption bands are about twelve in number, 

 running from X 5000 out into the violet, their width and dis- 

 tance apart decreasing in general with the wave-length. The 

 uranyl bands often appear in the absorption spectra of 

 uranous salts, and probably are due to the presence of 

 unreduced uranyl salt. Starting with the red end of the 

 series, the uranyl bands will be designated by the letters 

 a, b, c, d, &c. It has been found that the width, intensity 

 and wave-length of each one of the uranyl bands is 

 greatly modified by changing the solvent, by changing the 

 salt, by the presence of free acid, by a foreign salt or by 

 a change in temperature. Few if any other series of absorp- 

 tion bands can be so greatly modified by changing external 

 conditions as the uranyl bands, and any theory of absorption 

 spectra to be at all adequate must explain these changes. 



The absorption spectra of uranous acetate, bromide, 

 chloride and sulphate have been photographed in acetone, 

 methyl and ethyl alcohols, glycerol and water. The 

 absorption spectra of uranous bromide and uranous chloride 

 are very similar to each other and differ considerably from 

 uranous acetate. 



Acetone solutions of uranous salts give absorption spectra 

 that are quite different from the absorption spectra of these 

 same salts in other solvents. Even in the case of uranyl 

 salts the absorption spectra in acetone is characteristic of that 

 solvent. For example, uranyl chloride in acetone gives six 

 bands at XX 4980, 5000, 5030, 5240, 5270, and 5295. The 

 uranyl bands themselves are broken up into several compo- 

 nents. If a small amount of free hydrochloric acid is pre- 

 sent the d, e, / uranyl bands are broken up into triplets, each 

 triplet consisting of a strong central component and weaker 

 satellites about 20 A. U. wide. 



d. 



e. 



/• 



4470 



4340 



4205 



4430 



4290 



4100 



4385 



4250 



4120 



* Amer. Chem. Jo urn, xliii. p. 37 (1910), 



