104 



A STUDY OF THE ABSORPTION SPECTRA. 



different dielectric constant of the two different solvents. According to 

 such a theory the bands should gradually shift in position as one solvent 

 was increased and the other decreased in amount. Jones and Anderson, 

 however, found this not to be the case. They showed that there was a 

 definite set of methyl alcohol-bands and a definite set of water-bands. As the 

 amount of alcohol was decreased in a solution the alcohol-bands weakened but 

 remained in the same position. As the amount of water was increased the 

 intensity of the water-bands increased, but they remained in the same position. 

 These results were interpreted by them as being due to definite alcoholates and 

 hydrates that a definite alcoholate of neodj-mium had a characteristic 

 absorption spectrum. Recent work by E. E. Reid (Am. Chem. Jour., June, 

 1909) supports this theory. It should also be noticed that in general the 

 alcohol-bands are on the red of similar water-bands. 



One of the purposes of the present work was to find whether this 

 matter of a salt possessing a characteristic absorption spectrum in different 

 solvents was general or not. So far, it would seem to hold for uranyl 

 nitrate. We have seen that uranyl nitrate bands in methyl alcohol are all 

 nearer the red end of the spectrum than the corresponding water-bands. 

 This is not in agreement with the results of previous investigators. To 

 illustrate this we will give a table from Deussen's paper. 1 



Absorption spectra of uranyl nitrate in mixtures of water and methyl alcohol (Deussen). 



The general results of Deussen are very surprising indeed. In general, 

 he finds that by adding a little alcohol to an aqueous solution there is a 

 slight shift of the uranyl nitrate bands to the red. The position of the bands 

 then remains about the same w r ith increasing percentage of alcohol until 

 the solvent becomes almost pure alcohol, when there is a sudden shift 

 towards the violet. In our work we find nothing of this kind. We find 

 that in pure alcohol the bands are all shifted to the red as compared with 

 the water-bands. In order to study further these bands, and to learn 

 whether there was a gradual shift from alcohol-bands to water-bands, or 

 whether the alcohol-bands simply became fainter but remained in the 

 same position while the water-bands became stronger while remaining in 

 the same position as the percentage of water was increased, a set of solu- 

 tions was made up with varying amounts of water and alcohol; the 

 concentration of uranyl nitrate remaining constant at 0.1 normal. For 

 this purpose, of course, the anhydrous uranyl nitrate was used. Plate 66 

 represents two of the spectrograms. In A, starting with the strip nearest 

 the spark-spectrum the percentages of alcohol were 100, 92, 84, 76, 68, 60, 



1 Ann. Phys., 66, 1132 (1898). 



