EFFECT OF TEMPERATURE ON ABSORPTION SPECTRA. 79 



A, plate 53, represents the absorption of a methyl alcohol solution 0.2 



normal and with 1.0 cm. depth of cell. The temperatures are 25, 40, 55, 



and 70. The only important change clue to temperature is that at 70, the 



intense absorption near the center of the e group of bands having practically 



disappeared. 



Neodtmium Bromide in Methyl Alcohol. 



B, plate 54, represents the absorption spectrum of a 0.1 normal solution 

 of neodymium bromide in methyl alcohol. The length of cell was 10 cm. 

 The temperatures were 25, 35, 44, 60, 82, 100, and 120 C, beginning 

 with the lowest strip. At the highest temperature a slight precipitate was 

 formed, but still some light was transmitted. The neodymium solutions all 

 become much more deeply colored at the higher temperatures, and this can 

 easily be shown by heating such a solution in an ordinary test tube. 



The absorption spectrum of neodymium bromide in methyl alcohol is 

 quite different, as far as minute detail goes, from that of the chloride. In 

 general, the bands of the chloride are from 5 to 15 Angstrom units farther 

 towards the red than the bromide bands. 



For the lowest strip, very weak and diffuse bands appear at about X 4000, 

 X 4180, X 4600, X 4900, X 5040^ X 5320, X 6230, X 6260, X 6730, and X 6790. The 

 (3 group of the bromide is very different from that of the chloride. It consists 

 of a very sharp, narrow (3 units) band at X 4265, a very sharp and less intense 

 band at X 4275, a hazy band at about X 4280 which more or less overlaps 

 X 4275, and at higher temperatures X 4275 can not be noticed at all. A very 

 weak band appears at X 4300 and a broader band at X 4325, being about 20 

 Angstrom units in width. 



The 7 group of the chloride is also quite different from that of the bromide, 

 which has four bands of almost equal intensity at XX 4690, 4745, 4765, and 

 4815. Weak bands appear at X 4670, X 4700, and X 4725. The 5 group consists 

 of a rather narrow band at X 5090 and a very strong band at about X 5115; 

 a lot of narrow and intense bands at X 5200, X 5220, X 5235; X 5250 and X 5275 

 practically merge into a single band. The e group consists of a single wide 

 band extending from X 5700 to X 5880. 



As the temperature is raised the violet absorption increases quite rapidly, 

 and the 5 and e groups of bands become wider and stronger. The latter band 

 widens very greatly towards the red. All the bands become very much more 

 diffuse. This is particularly true of the /3 group, since at 120 only two very 

 hazy, indistinct bands appear, while at 25 some of the bands in this group 

 were almost as fine as spark lines. 



No measurable shift of the bands towards the red could be observed. 



That the absorption spectra of the chloride and the bromide in methyl 

 alcohol should be so different was quite unsuspected, since these two salts 

 have almost identically the same absorption spectra in aqueous solution. 



Neodymium Nitrate in Isobutyl Alcohol. 



The absorption spectrum of a solution of neodymium nitrate in isobutyl 

 alcohol was photographed at 20, 45, 75, 95, 110, and 120 C. The con- 

 centration was 0.05 normal and the depth of cell 10 cm. The first strip of 

 this spectrogram is described under the chapter on the mapping of spectra. 



