

Spectra of certain Uranous and Uranyl Compounds. 571 



at X 4920, c at 4750, and d at 4590. On adding water the 

 " acetone " bands gradually decrease in intensity, but are 

 not shifted, and the "water" bands b (A. 4980), c (X4700), 

 and d (X 4570) increase in intensity; both bands existing at 

 the same time. 



Uranous chloride in methyl alcohol has the distinct 

 "alcohol" bands c (X4770 and 4670) and d (X 4600). A 

 very typical example is that of the red " water " bands of 

 uranous chloride, bromide, and sulphate. There exists a 

 rather wide "water " band at X 6500, and another band at 

 X 6750 about 30 A.U. wide. As the anion at of uranous 

 chloride is increased these bands widen into one broad 

 band. 



Glycerol solutions of uranous salts give a broad b;md in 

 this region, but in no case does this ever break up into two 

 bands, except when free hydrochloric acid is present. In 

 marked contrast w*ith these solutions those in acetone, 

 methyl and ethyl alcohols show transmission throughout this 

 region. 



In mixtures of these solvents with w r ater the " water " 

 bands gradually decrease in intensity as the amount of water 

 decreases, but the wave-lengths are unchanged. "When 

 hydrochloric acid is added to an aqueous solution of uranous 

 chloride the X 6500 band becomes much narrower and the 

 X 6750 band widens. There are few if any s;dts that show 

 such characteristic "solvent" bands better than uranous 

 salts. 



The explanation of " solvent ,J bands seems to lie in the 

 fact that the salt forms a more or less definite compound 

 with the solvent. The persistence of the "solvent" bands 

 may be taken as a rough measure of the stability of these 

 compounds. 



The explanation of the gradual shift of the bands is much 

 more difficult. Larmor* suggests that loose aggregates, on 

 account of their mutual influence, would vibrate in longer 

 periods. In the case of uranyl bands, however, the different 

 bands are shifted by very different amounts, and apparently 

 the different bands are occasionally shifted in opposite direc- 

 tions. The study of the changes of the uranyl and uranous 

 bands during chemical changes should throw considerable 

 light upon the nature of the latter. A very good example is 

 the addition of nitric acid to uranous acetate in water. The 

 uranous acetate is gradually changed to uranyl nitrate. 



* Astrophye. Journ. xxvi. p. 120 (1907). 



