DISCUSSION OF EVIDENCE. 177 



bands. Further, the intensity of the solvent bands is a function of 

 the relative amounts of the solvents that are present in the mixture. 

 This, as has been pointed out, indicates the existence of hydrates in 

 the aqueous solutions and of alcoholates in solutions in alcohol, these 

 solvates having definite resonance and, therefore, definite absorption 

 spectra. 



One of the most striking examples of solvent bands is shown by the 

 absorption spectra of uranous chloride and bromide in a mixture of 

 water and methyl alcohol. We find two entirely distinct spectra, one 

 belonging to each solvent. Some lines and bands appear in the one sol- 

 vent which are entirely absent from the other, and practically all the 

 lines and bands have very different positions in the two solvents. To 

 see how differently the spectra appear, reference must be made to plate 

 23 of Publication No. 160 of the Carnegie Institution of Washington. 



The spectrum of uranous chloride in water is not only different from 

 the spectrum in methyl alcohol, but these are both different from the 

 spectrum in acetone. If we compare the spectra of this salt in the 

 three solvents, we might easily conclude that we were dealing with 

 three fundamentally different spectra, and the only change is in the 

 nature of the solvent. 



Uranous salts in solvents other than the above also show very 

 characteristic " solvent" bands. When ethyl alcohol is added to an 

 aqueous solution of uranous chloride, a marked change is produced 

 in the spectrum. The " ethyl alcohol" bands are quite different 

 from the " water" bands. The alcohol bands, or the water bands, 

 can be made the more intense by simply varying the relative propor- 

 tions of the two solvents. The addition of acetone to an aqueous 

 or methyl alcohol solution of uranous chloride produces a marked 

 change in the spectra. A number of acetone bands appear, these 

 being different from the " water" bands on the one hand, and from 

 the "alcohol" bands on the other. 



Uranous chloride dissolved in methyl alcohol has an absorption 

 spectrum very similar to that in ethyl alcohol. This would be expected, 

 on account of the close similarity of methyl alcohol and ethyl alcohol. 

 The methyl alcohol bands are of slightly shorter wave-lengths. 



The absorption spectra of uranous chloride in glycerol, and in mix- 

 tures of glycerol and water were also studied. A number of "glycerol " 

 bands manifested themselves, the glycerol absorption being very dif- 

 ferent from that of water. 



The absorption spectrum of uranous chloride in methyl alcohol and 

 ether was also studied. The solution in methyl alcohol showed com- 

 plete absorption in the ultra-violet to wave-length X 3700, while the 

 addition of ether extended the absorption to X 3800. The addition 

 of the ether caused the absorption to shift towards the red, the magni- 

 tude of this shift being from 10 to 30 A. u. 



