566 wick. 



Neodymium Acetate. 



The absorption of neodymium acetate 10 differs from that of the 

 other salts in that the bands are shifted toward the longer wave- 

 lengths and are much more diffuse. Single, unresolved bands appear 

 instead of the groups of narrower bands seen in the other salts at the 

 corresponding concentrations. A pressure of 1440 atmospheres 

 produces a slight intensification of the band at about 5800 and sepa- 

 rates it more distinctly into its two components. 



"Didymium" Nitrate. 



Didymium is a mixture of praseodymium and neodymium and the 

 spectrum of the nitrate is similar to that of the neodymium ammonium 

 nitrate and shows the same pressure effects. In the concentrations 

 used, aqueous solutions of didymium nitrate show very distinctly the 

 two components of band 4272 at normal pressure. At a pressure of 

 1700 atmospheres, the dimmer component practically disappears and 

 the stronger one becomes sharper and more intense. 



Effects of Changes in Temperature and Concentration upon 

 Neodymium Absorption Spectra. 



Effects very similar to those due to increase of pressure have been 

 observed as a result of the lowering of the temperature of neodymium 

 solutions. 11 Jones and his colleagues, in an extensive series of investi- 

 gations of aqueous solutions between 0° and 190°, found that all absorp- 

 tion bands have a tendency to become more diffuse at high tempera- 

 tures but that no marked change in the appearance of the bands takes 

 place except in the cases of 4272 and 5800, both of which remain fixed 

 on the violet edge and widen on the red edge diffusely with rise in 

 temperature. These two bands are the ones most changed by an 

 increase in pressure and it is observed that the effect of raising the 

 pressure is to produce an unsymmetrical narrowing similar to that 

 produced by a reduction of temperature. It is known from the work 

 of Becquerel, 12 Du Bois and Elias 13 and others, that the absorption 



10 Jones and Strong, Carnegie Publication, 130, p. 79. 



11 Jones and Strong, Carnegie Publication 130, pp. 72, 77, 83. Jones and 

 Guv, Carnegie Publication 190, p. 9. 



12 Becquerel, Phil. Mag., Vol. 16, p. 153, 1908. 



13 Du Bois and Elias, Ann. der Phys., Vol. 27, p. 233. 



