FROZEN SOLUTIONS. 205 



ENERGY DISTRIBUTION IN THE BANDS OF URANYL NITRATE. 



The normal aqueous solution at 90 was studied with the aid of 

 the spectrophotometer and bar, the intensity of the crests of the 

 bands being matched by the intensity of the acetylene flame at the 

 same wave-length. These values were multiplied by the ordinates of 

 the corresponding wave-lengths of the energy curve for acetylene. 1 

 Figure 107 shows the manner in which the bands differed in intensity. 

 The envelope is of the same form as that determined by Nichols and 

 Merritt 2 for the individual bands of the crystalline salts. 



SUMMARY OF CHANGES. 



The changes produced by slowly changing the temperature from 

 +20 to -180 include: 



(1) An increase in intensity of the entire spectrum. 



(2) A shift which is more often toward the violet than toward 



the red, although both shifts may occur between the above 

 temperatures. 



(3) A narrowing of the bands and in some solutions a resolu- 

 tion of the bands. 



(4) A slight change in the frequency interval. 



(5) The formation of one or more definite hydrates. 



(6) A change in the form of the bands. 

 The changes produced by dilution include: 



(1) A shift of the entire spectrum. 



(2) A change of interval. 



(3) A change in the hydrate. 



(4) A decrease in the resolution, excepting when small amounts 



of acid are added to an aqueous solution. 



(5) A decrease in intensity. 



CONCLUSIONS. 



(1) The constant-frequency intervals are due to the uranium oxide. 



(2) The small shifts are due to a change in the relative intensity of 

 two or more components of a band. 



(3) The more remarkable changes in position are caused by the 

 presence of a new hydrate. 



(4) The change in hydrate is probably often associated with a 

 change in the crystal system, and when this phenomenon occurs a 

 change in the grouping of the component bands occurs. The work 

 on four double nitrates 3 (Chapter VII) indicates that the crystal 

 system is an important factor in the determination of the positions of 

 the bands. 



(5) The invariable production of broad bands with extensive aqueous 

 dilution is due to complete ionization. 



1 Coblentz. Bureau of Standards, v. 7, No. 2, p. 259. 



2 Nichols and Merritt. Physical Review (1), 32, p. 358. 



3 Howes and Wilber. Physical Review (2), xi, p. 66. 1918. 



