84 A STUDY OF THE ABSORPTION SPECTRA. 



The absorption spectra of neodymium chloride have been photographed 

 in glycerol and alcohol solutions. There are indications of alcohol- and 

 glycerol-bands. The latter are more persistent than the alcohol-bands. In 

 the case of glycerol there seemed to be one band that gradually shifted 

 from the water to the glycerol position, indicating the possibility of the 

 existence of intermediate glycerolates. 



The effect of free nitric acid on the bands of neodymium nitrate is to 

 cause them to become much broader and more diffuse than the bands of 

 the neutral salt. Some of the bands are caused to broaden more on the red 

 than on the violet side. The effect of free nitric acid on the neodymium 

 bands is thus very different from the effect on the uranyl nitrate bands. 



Early in the work it was intended to alter conditions so that each band 

 could be followed throughout the various changes that it underwent. In 

 most cases, however, this is at present very difficult to do, on account of 

 the very sudden changes in the character of the spectra, and in many cases 

 also on account of the diffuseness of the bands. For instance, the band 

 X 4274 is certainly one of the most characteristic bands of the water-spec- 

 trum. In glycerol it is found that apparently this band gradually shifts 

 to X 4288 for a pure glycerol solution. For solutions containing a large 

 amount there appear fine satellites at X 4270 and X 4305. In alcohol the 

 band appears at X 4290. The band X 4274 does not, however, shift into 

 the alcohol-band. In a solution of neodymium nitrate in water as made 

 by Anderson there appear two strong bands close together, the distance 

 between the opposite edges being about 10 Angstrom units, and between 

 the adjacent edges, 2 Angstrom units. Neodymium nitrate and sulphate 

 crystals each give two strong components, but in this case the distance 

 between the opposite edges is 15 Angstrom units, and between the adjacent 

 edges 6 Angstrom units. In other words, in the neodymium nitrate crys- 

 tal the components are farther apart than in the nitrate solution as made 

 by Anderson. In the solutions made by Jones only one component 

 appears. A remarkable result manifests itself when the water of crystal- 

 lization of the sulphate and nitrate crystals is driven off. The rather 

 paradoxical effect is to cause the "X 4274 " bands to become weaker and 

 appear as a single band. In the case of neodymium nitrate, driving off the 

 water of crystallization causes many of the bands to be shifted towards 

 the red. For the sulphate the drying results in a shift of some bands to 

 the violet, while other bands remain unshifted. The dry nitrate bands in 

 several photographs made by Anderson are all of some 50 Angstrom units 

 greater wave-length than the dry chloride, dry sulphate, or crystal sulphate 

 bands. It is at present premature to attempt to interpret these changes, 

 since the intermediate steps have not been followed. Much work remains 

 to be done in this direction. 



In aqueous solutions it has been found that the absorption of neodym- 

 ium acetate is different from that of the chloride, bromide, and nitrate. 

 By adding inorganic acids to the acetate, photographs have been made of 

 the spectrum, as the acetate was changed to another salt. These spectra 

 indicate that in some of the reactions there probably exist several systems or 

 compounds between the acetate and the salt of the acid added. 



