SI) 



A STUDY OF THE ABSORPTION SPECTRA. 



It will be noticed that all the bands are 10 to 20 Angstrom units farther 

 to the red than the corresponding bands of the other neodymium salts. 



The A section of Plate 41 represents the effect of adding nitric acid to 

 a solution of neodymium acetate. The first strip of A contains nitric acid 

 and shows that the acetate bands have been shifted some 10 Angstrom 

 units towards the violet by this addition of acid. This shift occurs before 

 any other change of the acetate bands takes place. 



Plate 41, A, represents a spectrophotograph of the effect of adding 

 nitric acid to an aqueous solution of neodymium acetate. The addition 

 of nitric acid causes the absorption in the ultra-violet to increase. The 

 general effect on the neodymium bands is to cause the bands to become 

 sharper, and, then, as more and more acid is added, to make the bands 

 diffuse again. When the bands are sharpest they are practically the same 

 as the bands of neodymium nitrate in water. It requires the addition of 

 a very considerable amount of nitric acid to produce the nitrate neodymium 

 bands. A description of the plate is to be found on page 150. 



The group of bands in the region X 3500 in the first and seventh strips 

 appear to be slightly displaced to the red. In fact, all the " nitrate " bands 

 of the third and fourth strips are some 10 Angstrom units farther towards 

 the violet than the bands of the first and seventh strips. 



In strip 1 there is a strong band at X 5230 to X 5250. In strip 2 appears 

 a very fine and weak band on the shorter wave-length side of the wide band 

 at X 5240. In strips 3 and 4 the two bands are of equal intensity and are 

 located at X 5225 and X 5234. In strip 5 a band appears on the red side of 

 X 5234. At the same time X 5234 has become very much stronger than 

 X 5225. In strip 7 X 5225 has become very weak. In strip 7 there are weak 

 and fine bands at X 5205, 5225 and a band from X 5230 to X 5250. 



The group of bands at X 5800 behave in the same way. In strip 4 

 there are bands at XX 5730, 5755, 5775, 5800, and 5820. In strip 1 is a hazy 

 band at X 5750 and others at XX 5790, 5820, and 5870. In strip 7 there are 

 four bands, two at X 5730 to 5760 and two at X 5770 to 5830. The bands 

 XX 6800, 7040, and 7100 appear only in the central strips. 



A spectrogram was made to show the coexistence of the " water " and 

 ' alcohol ' : ' bands of neodymium chloride. The spectrogram is shown as 

 Plate 43, A. Anhydrous neodymium chloride was dissolved in a solution 

 containing 8 per cent water and 92 per cent ethyl alcohol. The first four 

 strips represent a Beer's law run, the concentrations being 0.5, 0.3, 0.1, and 

 0.05 normal, the most concentrated solution being the one whose spectrum 

 is next to the scale. The last three strips represent a constant concentra- 

 tion where the depth of cell is increased. 



