82 



A STUDY OF THE ABSORPTION SPECTRA. 



It will be seen that the addition of but a small amount of acid caused 

 the appearance of a large number of fine bands, especially in the region 

 of X 5800. It also caused a very considerable shift of all the bands to the 

 violet, an action similar to that of nitric acid. Further addition of acid 

 brought out a spectrum very similar to that of neodymium chloride as 

 shown by strips 3 and 4. Still further addition of acid produces other 

 changes, one being the appearance of new bands in the region X 5900. 



Plate 45, A, gives a spectrogram where known amounts of hydro- 

 chloric acid were added to an aqueous solution of neodymium acetate. 



A spectrogram (Plate 44, B) was made of mixtures in various propor- 

 tions of neodymium acetate and neodymium chloride in water. Strip 

 1 is the pure acetate and strip 7 the pure chloride. The intermediate strip 

 represents mixtures, the amount of chloride increasing from the bottom up- 

 wards. The concentration of neodymium was kept constant. 



From this spectrogram evidence is obtained that each of the two salts 

 has its own spectrum. As the amount of acetate is decreased the acetate 

 bands gradually decrease in intensity and finally disappear. At the same 

 time the chloride bands increase in intensity. 



The band X 5225 apparently is a chloride band, and does not appear 

 in the acetate solution. On the other hand, the band X 5830 and the very 

 diffuse band X 5860 appear to be acetate bands, and gradually disappear 

 as the amount of acetate decreases. 



