SPECTROPHOTOGRAPHY OF CHEMICAL REACTIONS. 57 



visible part of the spectrum. This line of work seems to be much more promis- 

 ing in the infra-red. 



It is known that, in the ultra-violet, anthracene and the neodymium 

 salts have absorption bands that are near together. It was, therefore, hoped 

 that a neodymium salt dissolved in anthracene would form aggregates con- 

 taining both of these compounds, and that the resultant absorption spec- 

 trum would not be simply the superposition of the two separate absorption 

 spectra of the given neodymium salt and anthracene. Unfortunately, the 

 neodymium salts that were tried were not soluble in anthracene, and it seems, 

 therefore, unlikely that we obtained aggregates containing both salts. Never- 

 theless, some spectrograms were taken with this idea in mind. Neodymium 

 nitrate and anthracene are both soluble in ethyl acetate, and several solutions 

 containing these three substances were prepared. It was found that only very 

 dilute solutions of anthracene allowed the ultra-violet part of the spectrum 

 to be transmitted, and no good photograph was obtained that showed the 

 anthracene and neodymium nitrate ultra-violet bands on the spectrogram. 

 It would seem very doubtful that any effect would be obtained, because of 

 the improbability of anthracene and neodymium nitrate being contained in 

 the same aggregate. 



A and B, plate 11, give the absorption spectrum of neodymium nitrate 

 and anthracene dissolved in ethyl acetate. In these spectrograms the ultra- 

 violet absorption is so great that none of the anthracene bands are shown. 

 A and B, plate 12, represent neodymium nitrate and anthracene in ethyl 

 acetate. The lower strip of B shows several of the ultra-violet bands of 

 anthracene, but does not show any of the neodymium ultra-violet bands. The 

 upper strip of B shows the neodymium bands quite clearly, and also the very 

 great general ultra-violet absorption. It is hoped that this effect can be 

 satisfactorily tested with reference to the theory of aggregates, especially in 

 the infra-red. 



THE URANYL AND URANOUS BANDS. 



The uranyl bands are usually ten or twelve in number and, starting at 

 about X 5000, have been designated by the letters a, b, c, etc., and form a series, 

 the head band being the a band. The uranous bands appear throughout the 

 spectrum and do not form any series. The uranous bands are characteristic 

 of the uranous salts, and spectrograms of the absorption spectra of a uranous 

 salt gradually oxidized into a uranyl salt by the addition of hydrogen peroxide 

 show the complete independence of the two spectra. 



A problem of considerable interest, and one that seems capable of solu- 

 tion, is the complete correlation of the a, b, c, . . . bands for the various 

 uranyl salts in each solvent. For most solvents the uranyl bands of the dif- 

 erent uranyl salts are very much alike. In aqueous solutions the differences 

 are very marked, but by taking spectrophotographs of the transformation of 

 one salt into another salt 1 Jones and Strong have succeeded in obtaining many 

 relationships of this kind. By extending the work to low temperatures, and 

 to the partly overlapping phosphorescent band spectra, it ought to be possible 

 to connect continuously the various changes that these bands undergo. 



1 Publication 130, Carnegie Institution of Washington. 



