66 A STUDY OF THE ABSORPTION SPECTRA. 



exposure to the spark was 4 minutes. Starting with the strip nearest the 

 comparison spectrum, the temperatures were 7, 20, 36, 51, 66, and 82. 



The absorption spectrum of the dilute solution is practically the same 

 as that for the concentrated solution. At 7 bands occur from X 4385 to 

 X 4490, X 4040 to X 4715, X 4810 to X 4840, X 5860 to X 5940 and a narrow 

 band at X 5980. 



The ultra-violet absorption at 7 extends to X 2650; at 82 it extends 

 to X 2750. The other bands are at XX 4385, 4490, 4650, 4715, XX 4805 to 

 4835, XX 5870 to 5930. The band X 5980 has become much more diffuse. 

 The band adjacent to it has also become narrower and much more filled up 

 by general transmission than at the lower temperatures. It will be seen 

 in general that there is very little if any temperature change in the ab- 

 sorption bands of praseodymium chloride at this concentration, except the 

 bands in the red, which become narrower and weaker at the higher temper- 

 atures. In the concentrated solution the change in this band was not as 

 great as in the dilute solution. In the concentrated solutions the other 

 bands widened slightly more than they do in the solution here described. 



The spectrogram (Plate 32, B) of an aqueous solution of praseody- 

 mium chloride shows the effect of change in temperature between 7 and 84 

 on a 2.56 normal solution 48 mm. deep. The exposure to the Nernst glower 

 (current 0.8 ampere and slit-width 0.20 mm.) was for 20 seconds. The ex- 

 posure to the spark was for 4 minutes. Starting from the comparison spec- 

 trum, the strips were taken at the temperatures 7, 20, 35, 51, 66, and 84. 



The spectrum-strip at 7 shows a large band in the blue and one in the 

 yellow. There is absorption in the ultra-violet. In the case of praseo- 

 dymium nitrate the absorption in the ultra-violet was probably due to the 

 N0 3 band. This absorption was found to be unaffected by temperature. 

 In the case of praseodymium chloride the absorption increases very 

 markedly with rise in temperature. At 7 the limits of the blue band are 



U I 4270 } and { 4930 } and for the y ellow band U 5750 and 610 - 

 There is slight absorption in the region X 5000 to X 5100, which is prob- 

 ably due to absorption bands. Two fine bands, each about 8 Angstrom 

 units wide, appear at XX 5220 and 5235. Absorption of the shorter wave- 

 lengths at 7 is complete to X 3100, at 51 X 3200, and at 84 X 3300. At 

 51 the blue band is located at XX 4280 and 4950, and the yellow band at 

 AA5740 and 6110. 



At 84 the limits of the blue band are XX 4280 and 4950, and of the 

 yellow band XX 5750 and 6110. The widening of the bands is very small 

 indeed. The fine bands XX 5220 and 5235 become much more diffuse and 

 at the higher temperatures could not be resolved at all. At 7, however, 

 the two bands were entirely separated. The blue and yellow bands are 

 very slightly affected by temperature within the ranges investigated. 



Praseodymium Nitrate. 



A spectrogram (Plate 32, A) showing the effect of rise in temperature 

 was made for a 2.6 normal aqueous solution of praseodymium nitrate 46.5 

 mm. deep. The exposures were made to the Nernst glower (current 0.8 



