44 A STUDY OF THE ABSORPTION SPECTRA. 



about X 2800. With rise in temperature this transmission band gradually 

 weakens and at 60 has practically disappeared. 



The Ions wave-length edge of the absorption band widens uniformly 

 with rise in temperature from X 4250 at 5 to X 4500 at 85. 



A spectrogram (Plate 21, A) was made of a 0.332 normal aqueous 

 solution of nickel chloride of 16 mm. depth of layer. The length of expos- 

 ure was 2 minutes to the Nernst glower, and 6 minutes to the spark. The 

 current through the Nernst glower was 0.8 ampere and the slit-width 0.20 

 mm. Starting with the strip nearest the comparison spectrum, the tem- 

 peratures of exposure were 5, 19, 33, 45, 60, 71, and 82. 



The absorption spectrum of nickel chloride under the above conditions 

 consists of a band in the violet, and more or less complete absorption in the 

 extreme ultra-violet. At 5 there is practically complete absorption to 

 X 2600. A diffuse absorption band runs from about X 3700 to X 4000. As 

 the temperature is raised the transmission in the ultra-violet is somewhat 

 increased. This is very peculiar, and is the first case thus far noticed of 

 transmission increasing in the ultra-violet with rise in temperature. At 

 71 the violet band has widened out so as to extend from X 3700 to X 4250. 



Nickel Sulphate. 



A spectrogram (Plate 16, B) was made of the absorption spectra of a 

 2-normal aqueous solution of nickel sulphate 3 mm. deep. The length of 

 exposure to the Nernst glower was 2 minutes and to the spark 6 minutes. 

 The current through the glower was 0.8 ampere and the slit-width 0.20 mm. 

 Starting with the strip nearest the comparison spectrum the temperatures 

 were 5, 19, 32, 47, 61, 72, and 81. 



Nickel sulphate is remarkable for the fact that it has practically no 

 absorption in the ultra-violet. The violet band at 5 extends from X 3700 

 to X 4200, and at 81 from X 3700 to ; 4350. It will thus be seen that the 

 effect of temperature on the absorption spectrum of nickel sulphate is 

 very small and consists simply in the violet band widening slightly in the 

 direction of the red. 



Nickel Acetate. 



A spectrogram (Plate 22, A) w r as made of a 0.5 normal aqueous solution 

 of nickel acetate, the depth of layer being 9 mm. The length of exposure 

 to the Nernst glower was 2 minutes, and to the spark 6 minutes. The 

 current in the glower was 0.8 ampere and the slit-width 0.20 mm. Starting 

 with the strip nearest the comparison spectrum, the temperatures were 6, 

 23, 38, 52, 64, 74, and 84. 



The absorption spectrum of nickel acetate is characterized by a band 

 in the violet and a slight absorption in the ultra-violet. At 6 the absorp- 

 tion in the ultra-violet is very small. At 84 it extends to about X 2600. 

 At 6 the violet band runs from X 3800 to X 4150. There is considerable 

 transmission in this region at the lower temperatures. At the higher 

 temperatures the limits of this band are XX 3700 and 4400. 



A spectrogram (Plate 22, B) of a 0.5 normal solution of nickel acetate 

 in water was made for various temperatures between 5 and 81, the depth 

 of layer being 3 mm. 



