1909-] OF VARIOUS SALTS IN SOLUTION. 207 



{g) Absorption Spectrum of Anhydrous Uranyl Nitrate. 



When it was first discovered that the uranyl nitrate " water " 

 bands were all shifted to the violet with reference to the bands of 

 the other uranyl salts in water, as well as with reference to the 

 uranyl nitrate bands in other solvents, it was thought that possibly 

 it was more hydrated than the other salts in solution. The uranyl 

 salts crystallize from water solutions at ordinary temperatures with 

 the following composition: UOo(N03)2.6H20, UOoSO^.sH^O, 

 U02(CH3COO),.2H.O, and UOXl^.H^O. This fact would favor 

 the supposition that in solution the nitrate might be more hydrated 

 than the other salts. The fact that the absorption of the aqueous 

 solution of the nitrate and the crystallized salt was very much the 

 same as far as the positions of the uranyl bands is concerned, also 

 seemed to favor this view. 



In this connection it was considered important to examine the 

 absorption spectrum of the anhydrous uranyl nitrate. The salt was 

 powdered and placed in a closed glass tube just above the slit of 

 the spectroscope. The light of a Nernst glower was then focused 

 upon the surface of the salt nearest the slit and an exposure of 

 about three hours made. In this way we examine light that has 

 penetrated a short distance into the powder and is then diffusely 

 reflected. 



The absorption spectrum was found to consist of quite a large 

 number of bands, which seem quite different in many respects from 

 those of the solution. The following are the approximate wave- 

 lengths: AA4800, 4650, 4500, 4420, 4360, 4280, 4180 (broad), 4060 

 (broad), 3950 (broad), 3820 (broad), 3700 (narrow) and 3600 

 (narrow). The bands marked broad are from 50 to 60 Angstrom 

 units wide and the narrow bands about 20 Angstrom units. If the 

 first band is the a band, then the bands of the anhydrous salts are 

 to the violet of the corresponding bands of the crystals and of the 

 solution. If it is the b band the opposite is the case. On account 

 of the smallness of the intensity of the bands it could not be settled 

 whether A 4800 is the a or the b band. Further investigation of this 

 point will be made. 



There are two difficulties to the above theory, difficulties for 



