40 A STUDY OF THE ABSORPTION SPECTRA. 



The ultra-violet absorption reached to about X 3000, with a great deal 

 of general absorption throughout the violet. This general absorption 

 increased slightly with rise in temperature. At 1.5 there was transmis- 

 sion to X 6900, and at 20 to X 6800. At 20 and 30 the cobalt bands show 

 quite strongly at XX 6100, 6240, 6400. At 45 the absorption reaches to 

 X 6050, at 57 to X 5950, at 74 to X 5850, and at 88 to X 5800. 



"Wide bands appear at approximately X 5000 and X 5300. These bands 

 are very weak, considerably weaker than for a solution of cobalt chloride 

 and aluminium chloride. 



Cobalt Sulphocyanate. 



A spectrogram (Plate 20, A) was made to show the effect of change in 

 temperature on a 2-normal aqueous solution of cobalt sulphocyanate 

 (CoS 2 C 2 N 2 ), 1 mm. deep. The length of exposure was 3 minutes to the 

 Nernst glower, the current being 0.8 ampere and the slit-width 0.20 mm. 

 The length of exposure to the spark was 6 minutes. Starting with the strip 

 nearest the comparison scale, the temperatures were 3, 18, 31, 45, 59, 

 and 80. 



Under these conditions of concentration and depth of layer the cobalt 

 sulphocyanate absorption consists of an ultra-violet absorption band and 

 a wide band in the yellow and green. As the temperature is raised these 

 bands both widen out on the red side. The effect of temperature is espe- 

 cially marked between 60 and 80. The limits of the ultra-violet absorp- 

 tion are X 3400 at 3, X 3450 at 18, X 3450 at 31, X 3500 at 45, X 3550 at 

 59, and X 3600 at 80. 



For the yellow-green band the limits are X 4550 to X 5600 at 3, X 4550 

 to X 5630 at 18, X 4550 to X 5650 at 31, X 4570 to X 5700 at 45, X 4550 to 

 >l 5750 at 59, and X 4550 to X 6400 at 80. At 59 there is a weak and broad 

 band extending from X 6000 to about X 6300. 



The remarkable feature of this spectrogram is that the yellow-green 

 band widens only on the red side. 



A spectrogram (Plate 20, B) was made of a much more dilute solution 

 of cobalt sulphocyanate in water, the concentration being 0.25 normal 

 and the depth of cell 8 mm. The time of exposure to the Nernst glower with 

 a current of 0.8 ampere and a slit -width of 0.20 mm. was 2 minutes. The 

 length of exposure to the spark was 6 minutes. Starting with the strip 

 adjacent to the comparison spectrum, the temperatures were 6, 20, 33, 

 47, 59, 73, and 80. 



In this spectrogram the effect of temperature on the absorption 

 spectra of cobalt sulphocyanate was very small as compared with the 

 effect on the 2-normal solution. At 6 the ultra-violet band absorbed pretty 

 completely up to X 3220. There was a slight transmission of light where a 

 strong spark-line was located, but this was small. The edge of the band 

 was quite sharp. The yellow-green band extended from X 4600 to X 5500. 

 At 80 the ultra-violet band has absorbed everything to X 3300. The yellow- 

 green band at this temperature runs from X 4600 to X 5600, showing a slight 

 widening on the side of the longer wave-lengths. 



