CHROMIUM SALTS. 53 



Chromium Nitrate. 



Two spectrograms were made of chromium nitrate in water, one 

 (Plate 26, A) of a 0.754 normal concentration and 3 mm. depth of cell, and 

 the other (Plate 26, B) a 0.094 normal concentration and 24 mm. depth of 

 cell. The concentrated solution was exposed 2 minutes and the dilute solu- 

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

 0.20 mm. Both spectrograms were made using a 6 minutes exposure to the 

 spark. Starting with the strip nearest the comparison scale the tempera- 

 tures of exposure of the concentrated solution to the light were 5, 17, 

 32, 45, 60, 70, and 81, and of the dilute solution 7, 17, 33, 44, 59, 

 69, and 83. 



Chromium nitrate under the conditions here described shows three 

 bands, the N0 3 band in the ultra-violet, a band in the blue and violet and 

 a wide band in the yellow and green. For the concentrated solution the 

 temperature effect on the N0 3 band is small, the absorption being about 

 50 Angstrom units greater at the higher temperature. At 5 the limit of 

 this band is X 3220. The blue-violet band extends from X 3700 to X 4500 

 and the yellow-green band from X 5100 to X 6300 at 6. At 81 the blue- 

 violet band extends from X 3700 to X 4600 and the yellow-green band from 

 X 5100 to X 6450. For all the temperatures there was a band at about 

 X 6750. This band was unaffected by temperature. 



At 7 the ultra-violet band of the more dilute solution extends to X 3200 

 and is about 50 Angstrom units wider at the higher temperature. The blue- 

 violet band at 7 runs from X 3650 to X 4400, at 83 X 3750 to X 4600. The 

 yellow-green band at 7 runs from X 5400 to X 6150. At 83 it has widened 

 out from X 5350 to X 6400. 



A spectrogram was made showing the effect of temperature on the 

 absorption spectra of a 0.754 normal aqueous solution of chromium nitrate, 

 the depth of layer being 1 mm. The times of exposure were 5 minutes to 

 the spark and 2 minutes to the Nernst glower, current being 0.8 ampere and 

 width of slit 0.20 mm. The temperatures, starting with the strip adja- 

 cent to the comparison spectrum, were 5, 17, 30, 44, 58, 72, and 82. 



The absorption spectrum of chromium nitrate under the above named 

 conditions consists of a weak transmission band at X 2800. At 5 this band 

 is about 300 Angstrom units wide. As the temperature is raised the 

 transmission weakens, but there is so much general transmission that the 

 stronger spark lines usually show more or less evenly throughout the absorp- 

 tion, which at 5 extends from X 3000 to X 4200. At 82 there is a complete 

 absorption of all the short wave-lengths up to X 4500. Like all other bands 

 for chromium solutions, the edges are very broad and diffuse. At the higher 

 temperatures there seemed to be somewhat greater absorption in the red 

 at X 6800. 



Chromium Sulphate. 



A spectrogram (Plate 28, B) was made of an aqueous solution of 

 chromium sulphate of 0.125 normal concentration and a depth of cell of 

 3 mm. The length of exposure was 4 minutes to the Nernst glower at 0.8 

 ampere, and 6 minutes to the spark. The slit-width was 0.20 mm. The 



