74 A STUDY OF THE ABSORPTION SPECTRA. 



At 82 the general absorption has increased in the ultra-violet and has 

 reached to about X 2800. It will be noticed here that the effect of rise in 

 temperature upon this general ultra-violet absorption is greater for the 

 dilute solution than for the concentrated solution which has been pre- 

 viously described. 



The band XX 3455 to 3575 at 5 has widened slightly, having the limits 

 XX 3445 and 3580 at 82, the widening being about 15 Angstrom units. This 

 band in the concentrated solution widened 60 Angstrdm units. Practically 

 no effect on the bands from X 4200 to X 4900 is to be noticed with rise in 

 temperature. At the higher temperature the bands are slightly more diffuse, 

 but this change is very small. The band XX 5020 to 5290 at 5 has widened 

 to ?J. 5015 and 5285, about 10 Angstrom units. The corresponding widen- 

 ing for the concentrated solution was approximately 50 Angstrom units; 

 although it must be noted that in the more concentrated solution this 

 widening was mostly due to the increased absorption of the band X 5310 

 at the higher temperatures. The band X 5685 to X 5920 at 5 has widened 

 to XX 5775 and 5930, about 20 Angstrom units, compared with a widening of 

 55 Angstrom units for the more concentrated solutions. None of the other 

 bands show any appreciable change with change in temperature. 



A spectrogram (Plate 39, A) was made showing the effect of tempera- 

 ture on the absorption spectrum of a 1.66 normal aqueous solution of 

 neodymium bromide, the depth of layer being 6 mm. An exposure of 4 

 minutes was made to the Nernst glower (0.8 ampere and a slit-width of 0.20 

 mm.). The length of exposure to the spark was 6 minutes. The tempera- 

 tures, starting with the strip adjacent to the comparison spectrum, were 4, 

 20, 36, 50, 68, and 83. 



At 4 there is complete absorption in the ultra-violet up to X 2600. 

 A broad absorption band appears at X 2660 to X 2800 and from X 2950 to 

 X 3060. These absorption bands appear with a more or less general absorp- 

 tion. Bands appear at XX 3460, 3500, and 3540. The band at X 4274 is weak. 

 Weak and diffuse bands occur at XX 4440, 4630, 4695, 4825, 5095, 5260, 

 6810, and 6900. Wider bands are located at XX 5116 to 5140, XX 5200 to 

 5240, and XX 5710 to 5850. 



At 83 the spectrum is almost exactly the same as at 4. The ultra- 

 violet absorption is complete up to X 3050. The bands at X 3500 have 

 increased in width slightly and the band X 4274 is slightly broader. The 

 bands that have widened appreciably are XX 5195 to 5260 and XX 5700 to 

 5880. The change in the absorption is greater when the temperature is 

 changed from 68 to 83. Up to 68 there is practically no change in the 

 absorption spectrum at all. 



A spectrogram (Plate 39, B) showing the effect of temperature was 

 made, using a 0.055 normal aqueous solution of neodymium bromide, the 

 depth of layer being 197.4 mm. This spectrogram was made for comparison 

 with that for a 1.66 normal solution of the same salt 6 mm. deep. The 

 exposures to the Nernst glower lasted 90 seconds in this case (current 0.8 

 ampere and slit-width 0.20 mm.). The length of exposure to the spark was 

 6 minutes. Starting with the strip nearest to the comparison scale, the 

 temperatures of the solution were 5, 16, 29, 42, 55, 68, and 84. 



