72 A STUDY OF THE ABSORPTION SPECTRA. 



The X 4690 band is common to solutions of both neodymium and pra- 

 seodymium, and this has led some to believe that there is a common element 

 in these two substances. Stahl considers the view that there are several 

 elements in neodymium as very improbable. 



The Effect of Rise in Temperature on the Absorption Spectra of Aqueous 



Solutions of Neodymium Salts. 



A spectrogram (Plate 38, A) of a 3.4 normal solution of neodymium 

 chloride in water, 43 mm. deep, was taken. The exposures were made for 

 3 minutes to the Nernst glower, the current being 0.8 ampere and slit- 

 width 0.20 mm. The time of exposure to the spark was 6 minutes. Start- 

 ing with the strip nearest to the comparison spectrum, the temperatures 

 were 6, 21, 36, 47, 60, 77, and 83. 



Neodymium chloride, under the conditions of this experiment, gives 

 a complete absorption in the ultra-violet up to X 3700. From X 3700 through- 

 out the violet and blue regions there is almost complete general absorption, 

 this general absorption increasing with the temperature. A band of ab- 

 sorption seems to appear at about X 4000, but this is somewhat doubtful. 

 A very sharp and strong band appears at X 4185. A band occurs at X 4265 

 to X 4305 and one at X 4320 to X 4350. The transmission band between these 

 two bands is faint and disappears at 77. An absorption band extends 

 from X 4380 to X 4520 and there is then complete absorption up to a 4980. 

 The transmission between these bands is very weak and has almost dis- 

 appeared at 83. Between X 4970 and X 5365 there is an absorption band, 

 the long wave-length edge of this band being extremely sharp. A similar 

 band lies between X 5620 and X 6000. Next comes a series of five absorption 

 bands. The first of these is 20 Angstrom units wide and is at X 6250, 

 the next is 10 Angstrom units wide and is at X 6270. The bands XX 6295 

 and 6315 almost touch each other, the distance between them being but 

 two or three Angstrom units. The last band is about 30 Angstrom units 

 in width and its center lies at X 6380. The last band that could be photo- 

 graphed was between X 6720 and X 6965. 



The effect of rise in temperature is quite evident, most of the bands 

 widening and their sharpness gradually decreasing. At 83 the band 

 X 4970 to X 5365 described above has widened to X 4960 and X 5395, the 

 widening being slightly greater on the red side. The band X 5620 to X 6000 

 has widened to XX 5610 and 6050, this widening also being unsymmetrical. 

 The five bands in the vicinity of X 5800 at 6 have merged into three bands. 

 The red band is at XX 6720 to 6990. It will thus be seen that the widening 

 is in general greater on the red side of the bands. 



A spectrogram (Plate 37, A) of the absorption spectrum as affected 

 by change in temperature was made for a neodymium chloride solution 

 in water, the concentration being 3.4 normal and the depth of layer 12 mm. 

 The length of exposure was 2 minutes to the Nernst glower (current 0.8 

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

 6 minutes. Starting with the strip nearest the numbered scale, the tem- 

 peratures were 11, 22, 33, 45, 59, 73, and 85. 



At 11 an absorption band appears at about X 2970, a very strong band 

 from X 3250 to X 3285, and an adjacent band from X 3285 to X 3310. A very 



