76 A STUDY OF THE ABSORPTION SPECTRA. 



G900, grow fainter and fainter with rise in temperature, and have practically 

 disappeared at 82. The band X 6245 is very weak at 6 and has disap- 

 peared at about 60. 



It will thus be seen that not only does the presence of calcium chloride 

 modify greatly the absorption of neodymium chloride, but that it changes 

 the effects due to temperature very fundamentally. In pure neodymium 

 chloride practically no bands decrease in intensity with rise in temperature, 

 and at present no shift has been detected. When calcium chloride is added 

 to the solution most of the bands decrease in intensity with rise in tempera- 

 ture and several are shifted towards the red at the same time. Several 

 bands disappear. Moreover, although the band XX 6800 to 6900 widens, 

 this widening is entirely on the red side, whereas for the pure neodymium 

 chloride solution this widening always takes place on both sides of the band. 



A spectrogram (Plate 40, B) was made to show the effect of change 

 in temperature on a 2.15 normal aqueous solution of neodymium nitrate. 

 The length of layer was 3 mm. The exposures were for 40 seconds to the 

 Nernst glower (current 0.8 ampere, slit-width 0.20 mm.). The length of 

 exposure to the spark was 6 minutes. Starting with the strip nearest the 

 comparison spectrum, the temperatures recorded were 4, 17, 29, 43, 58, 

 71, and 84. 



The changes in the spectrum due to this change in temperature of 

 80 were very slight. The N0 3 band extends to about X 3250 at 4, and to 

 about X 3280 at 84. The bands at X 3500 became considerably wider and 

 their edges more diffuse at the higher temperatures. At the lower tem- 

 peratures fine bands appear at XX 5210, 5225, and 5240. At 84 these bands 

 all merge into a single band. The red band extends from X 5705 to X 5860 

 at 4. The band at X 5820 is very faint at the lower temperatures. At 84 

 it is unrecognizable. At this temperature the red band extends from X 5700 

 to X 5880. The widening of this band for the concentrated solution is 

 somewhat greater than for the dilute solution, but the effect of concentra- 

 tion is very slight. This is to be expected since the effect of temperature 

 itself is so very minute. 



A spectrogram was made of a 1.66 normal aqueous solution of neodym- 

 ium bromide 54.6 mm. deep. The exposures were 3 minutes to the Nernst 

 glower and 6 minutes to the spark. The current in the Nernst glower was 

 0.8 ampere and the slit-width 0.20 mm. Starting with the strip nearest the 

 comparison scale, the temperatures were 6, 20, 33, 47, 62, 73, and 82. 



The effect of rise in temperature on the absorption spectra of this 

 salt was quite marked, practically all of the bands broadening and becom- 

 ing more intense. At 6 the ultra-violet absorption extended to X 3600. 

 At 82 it had advanced to X 3800. Very narrow and fine bands appear at 

 XX 4186, 4300, 4308, 4345, 6240, 6265, 6290, 6305, and much broader bands at 

 X 6380 and X 6740. Wide bands occur from XX 4390 to 4480, XX 4550 to 

 4850, XX 4990 to 5340, XX 5650 to 5950, and XX 6760 to 6930, at 6. At 82 

 these bands have the following limits, respectively: XX 4380 to 4500, XX 4540 

 to 4910, XX 4960 to 5370, XX 5620 to 5990, and XX 6730 to 6960. 



A spectrogram (Plate 38, B) was made of a 2.96 normal aqueous 

 solution of neodymium nitrate 38.5 cm. deep. An exposure of 3 minutes 



