56 



ATLAS OF ABSORPTION SPECTRA. 



179. Potassium Permanganate Continued. 



the method used, the bands do not 

 shift at all* Trichromatic plates 

 were used to see if any photographic 

 bands less refrangible than 0.570^ 

 could be recorded. No evidence of 

 the existence of such bands was pre- 

 sented. 



180. Praseodymium Ammonium Nitrate. 

 Fig. 100, pi. 26. 



Yellowish-green crystals. In solu- 

 tion yellowish green. 



Concentrated (filtered). 



The solution was poured into a 

 quartz cell, the ends of which were 

 plane and parallel. The cell was 

 successively adjusted to the fol- 

 lowing depths, viz: 0.73, 1.03, 1.33, 

 1.63, 1.93, 2.23, 2.53, and 2.83 cm. 

 In other words, the thickness of 

 the absorbing layer was increased 

 by 3 mm. between the successive 

 photographic exposures. 



The solution is remarkable for the 

 comparative narrowness and great 

 intensity of its absorption bands. 

 Absorption was complete from 

 0.20/X to about 0.333/* and 0.343/i, 

 respectively, for the least and 

 greatest depths of solution investi- 

 gated. The centers of the four in- 

 tense bands which fell within the 

 region of sensitivity of the Seed 

 emulsion were at wave-lengths 

 o.4445/t, 0.4685/x, 0.4820/1, and 

 0.590/i. The least refrangible side 

 of the band at 0.590/t does not ap- 

 pear in fig. 100 because the band 

 came very near the limit of sensi- 

 bility of the photographic film em- 

 ployed. 

 181. Sodium Bichromate. 



Suggested by fig. 14, pi. 4. 



Orange-red crystals. In solution 

 yellow, pale yellow. 



Very dilute solution. 



Angle 50.7'. Depth o to 0.46 mm. 



181. Sodium Bichromate Continued. 



The spectrogram differs from fig. 14 

 in having the ultra-violet absorp- 

 tion curve displaced bodily to- 

 wards the region of the shortest 

 wave-lengths. Absorption was 

 practically complete from o.20/t to 

 about 0.27/i, for all depths. At the 

 thickest part of the liquid wedge 

 absorption was complete from o.20/i 

 to 0.40/1, but both the photographic 

 strip adjacent to the comparison 

 spectrum and the one in the mid- 

 dle of the spectrogram recorded a 

 comparatively narrow band of 

 semi-transparency, the center and 

 maximum of which was near 

 0.318/*. This was followed by a 

 strong, round absorption band 

 whose maximum was at 0.36/1. In 

 other words, there were two round, 

 ultra-violet bands of absorption 

 which coalesced at the wave- 

 length 0.318/4. Transmission was 

 complete from 0.40/1 to 0.63/*. 



182. Sodium Nitroprussid. 

 I'ig. 76, pi. 19. 



Garnet crystals. In solution reddish 

 brown, light brown. 



Saturated. 



Angle 1 45'. Depth o to 0.96 mm. 



Weak absorption in violet. Light 

 from the spark decomposes the 

 solution at the very beginning of 

 illumination so that the method 

 used for photographing the ultra- 

 violet absorption of the perman- 

 ganates was not applicable. This 

 difficulty was not overcome. Ab- 

 sorption decreases to about 0.38/4, 

 then increases to a weak maximum 

 near 0.396/1, and finally decreases 

 to transparency at 0.428/1. No 

 selective absorption from 0.43/1 to 

 0.62/i. 



183. Water. See No. 148. 



*See H. Kayser."Handbuch der Spectroscopic," v. iii, p. 415. 



