54 A STUDY OF THE ABSORPTION SPECTRA. 



temperatures, starting with the strip nearest the numbered scale, were 5, 

 20, 37, 51, 66, and 82. 



At 5 the three characteristic chromium bands appear the ultra- 

 violet band extending to X 2800, the blue-violet band from X 4100 to X 4450 

 and the yellow-green band from X 5500 to X 6200. The bands at X 6800 

 appear but very faintly. Throughout the visible portion of the spectrum 

 there is a very strong absorption, as will be noticed from the extremely 

 long exposure of 4 minutes to the Nernst glower. 



At 82 the ultra-violet band extends to X 2900, the blue-violet band 

 from X 4100 to X 4550 and the yellow-green band from X 5500 to X 6300. 

 The effect of temperature was very small, being in general the shifting of 

 the long wave-length edges of all three bands towards the red. 



Chromium Acetate. 



A spectrogram showing the effect of rise in temperature on the absorp- 

 tion spectra of a 10 mm. solution of 0.125 normal chromium acetate was 

 made. The slit-width was 0.20 mm. Exposures were made to the Nernst 

 glower for 4 minutes, the current being 0.8 ampere. Exposures to the 

 spark were continued for 6 minutes. Starting with the strip nearest 

 the comparison scale, the temperatures were 5, 20, 36, 52, 64, and 78. 

 The absorption remained practically independent of the temperature. 



Chromium acetate under the present conditions of concentration and 

 depth of cell shows a faint transmission band in the green between XX 5000 

 and 5200. Except for a few faint bands there is transmission of all the 

 longer wave-lengths beyond X 6400. The whole blue, violet, and ultra- 

 violet regions are absorbed, as is also the whole region between X 5200 and 

 X 6400. There is an absorption band at X 6490, which resembles very much 

 one of the larger uranyl bands. It is about 60 Angstrom units wide. The 

 short wave-length edge of this band is very diffuse and looks very much as 

 though the band were complex. There is a narrow band at X 6550. This 

 band is but 10 Angstrom units wide. Narrow bands very much like this 

 one appear at XX 6510, 6800, 6860, 6920, 6970, and 7030. The smaller 

 bands are very faint and in the spectrum-strip at 78 practically disappear. 



A spectrogram was made of chromium acetate, 0.125 normal concen- 

 tration in water and 3 mm. depth of cell. The exposures were 3 minutes to 

 the Nernst glower at 0.8 ampere, and slit-width 0.20 mm. The length of 

 exposure to the spark was 6 minutes. The temperatures were 5, 19. 37, 

 50, 64, and 79. 



The effect of change in temperature in this chromium salt was very 

 small, the only noticeable change b nng a slight increase in the intensity of 

 the yellow band. The whole ultra-violet was absorbed up to X 3800. From 

 X 3800 to X 4600 there was a very strong general absorption. There was 

 also strong absorption in the yellow. 



Chrome Alum. 

 A spectrogram (Plate 28, A) gives the effect of rise in temperature on 

 the absorption spectra of chrome alum. It will be seen that the violet and 

 ultra-violet bands are widened but slightly. The other chromium band in 

 the yellow is slightly widened. 



