CHAPTER VII. 



GENERAL SUMMARY OF RESULTS. 



The work on the effect of temperature on the absorption spectra of .solutions 

 was extended to aqueous solutions, the range in temperature being from 

 ordinary temperatures up to about 200. For this purpose a special form of 

 apparatus was constructed, made of brass and lined on the inside with gold. 

 This was for the purpose of preventing the hot vapor under high pressure 

 from coming in contact with any metal except gold. 



With this apparatus the absorption spectra of aqueous solutions could be 

 studied up to 200, just as well as the spectra of nonaqueous solutions in the 

 apparatus used by Jones and Strong, and described in Publication of the 

 Carnegie Institution of Washington No. 160. 



With neodymium chloride the following bands remain unchanged by 

 temperature over the range from 20 to 200: X3800, X4025, X4200, X4325, 

 X4440, X4600, X4690, X4750, X4820. The double band X5050 to X5270 

 changes very slightly. The bands X4275 and X5800 show marked changes, 

 the red edge widening and becoming more diffuse. The X5800 band widens 

 as much as 50 a.u. toward the red, the violet edge remaining sharp. 



With the neodymium bromide, as with the chloride, only X4275 and X5800 

 show any marked changes with rise in temperature. The band X5800 widens 

 for the bromide 60 a.u. from 20 to 190. 



The X4275 band, for neodymium nitrate, shows a marked change, widen- 

 ing towards the red. The X4425 band widens about 15 a.u. from 15 to 165. 

 The bands X5125 and X5800 show marked changes towards the red. The 

 change was greatest in the most concentrated solutions, although the total 

 number of absorbers in the path of light was kept constant. 



The bands X4275 and X5800 for neodymium acetate show marked changes 

 on the red side, the latter widening as much as 80 a.u. The acetate bands, 

 for a given concentration of salt, are the most intense of all the neodymium 

 bands. When the solution was cooled down, the absorption spectra went 

 through exactly the reverse changes as when the temperature was raised. 

 Since the acetate band, X5800, is more intense for the same concentration 

 than for neodymium chloride or nitrate, and since the acetate is less dis- 

 sociated than the neodymium salts of the strong acids, it appears probable 

 that this band is in some way connected with the molecules. 



The sulphate of neodymium shows the same temperature effect as the 

 other salts of this element. 



The effect of temperature on the absorption spectra of cobalt chloride is 

 very slight. 



There is a slight widening of the band of praseodymium chloride whose 

 center is near X4825. The X5900 band undergoes slight change with tem- 



85 



