NEODYMIUM SALTS. 77 



was made to the Nernst glower, the current being 0.8 ampere and the slit- 

 width 0.20 mm. The length of exposure to the spark was 6 minutes. 

 Starting with the strip nearest the comparison scale the temperatures 

 were 7, 17, 30, 44, 59, 70, and 82. 



At 7 there is practically complete absorption in the ultra-violet up 

 to X 4600, due to the absorption of the N0 3 group. The edge of the band 

 is very sharp. Other bands are as follows: A 4270 to X 4288, X 4386 to 

 X 4500, X 4538 to X 4870, X 4970 to X 5370, X 5620 to X 6005, X 6240 to X 6270, 

 and X 6705 to X 6970. 



It should be noticed here that the absorption spectrum of neodymium 

 nitrate under the present conditions is quite different from the absorption 

 of a similar solution of neodymium chloride. In the case of the chloride 

 there was a very great amount of absorption throughout the ultra-violet 

 and violet portions of the spectrum. In the case of the nitrate there is 

 almost complete absorption up to X 3600 and from that wave-length to 

 X 4270 there is complete transmission. In this region appeared several 

 narrow and sharp bands in the neodymium chloride absorption spectrum. 



From the spectrum shown in the upper strip and for which the tempera- 

 ture was 82 we see that the N0 3 band extends to X 3615. The band X 4274 

 has become about 5 Angstrom units wider than it was at 7. A wide and 

 weak band appears at X 4350, and this is considerably stronger than at the 

 lower temperatures. The positions of the other bands are: X 4380 to 

 X 4560, X 4535 to X 4870, X 4970 to X 5390, X 5615 to X 6025, and X 6700 to 

 X 6970. The increase in width of these bands due to raising the temper- 

 ature from 7 to 82, is 60, 20, 25, and about Angstrom units, respectively. 



A spectrogram was made of the absorption spectra of a 2.15 normal 

 solution of neodymium nitrate 3 mm. deep. Starting with the strip nearest 

 the numbered scale, the temperatures were 4, 17, 29, 44, 58, 71, and 84. 



As the temperature rises the N0 3 band widens slightly. The bands 

 in the region of X 3500 become more diffuse and slightly wider. The same 

 is true of the bands at X 5200. The broad band at X 5800 widens, especially 

 on the long wave-length edge. 



A spectrogram (Plate 40, B) was made of a very dilute solution of 

 neodymium nitrate in aqueous solution of 0.036 normal concentration and 

 197 mm. depth of cell. The length of exposure to the Nernst glower was 

 20 seconds, current being 0.8 and slit-width 0.20 mm. The length of ex- 

 posure to the spark was 5 minutes. Starting with the strip nearest the com- 

 parison spark-spectrum, the temperatures were 9, 22, 42, 56, 69, and 78. 



The effect of temperature on the absorption of neodymium at this 

 concentration is very slight. At 9 there is almost complete absorption 

 up to X 3300, due to the N0 3 band. Bands are located at X 3460, X 3500, 

 X 3530, X 4273 (weak), X 4445, X 4610, X 4692, X 4756, X 4820, X 5093, X 5136, 

 X 5197 to X 5247, X 5255, X 5330, X 5705 to X 5860, X 6800 and X 6900. 



At 78 the N0 3 has advanced about 30 Angstrom units towards the 

 red. The bands in the region of X 3500 have widened slightly. The inten- 

 sities of the other bands have changed but little. The wide band in the 

 red extends from X 5705 to X 5875, there being a slight widening on the long 

 wave-length edge of the band. The bands X 6800 and X 6900 are slightly 



