MISCELLANEOUS ABSORBING MEDIA. 



49 



157. Cobalt Chloride, etc. Continued. 



solutions of the series were 0.000, 

 1. 118, 1.394, 1.676, 1.781, 1.887, 

 2.096, and 2.459 normal. 



The solution which contained no dehy- 

 drating agent only absorbed the con- 

 tinuous background from 0.2O/U, to 

 O.23IJH. The band in the blue-green 

 extended from 0.503/i to about 

 0.530/1. 



The solution of concentration 2.096, 

 in the aluminium chloride, absorbed 

 the continuous background from 

 o.20fji. to 0.288/x. The iiand in the 

 blue-green extended from 0.485/x to 



0.555M- 



The absorption in the yellow and 

 orange is brought out clearly by the 

 photographic strip adjacent to the 

 comparison spectrum. The changes 

 which the bands in the orange and 

 red undergo when the amount of 

 dehydrating agent in the solutions is 

 increased are pronounced and inter- 

 esting, but they are too complicated 

 to admit of discussion in this place.* 

 Similar changes are brought about 

 by other dehydrating agents, such 

 as calcium chloride, for example. 



Figure 95 illustrates the fact that the 

 absorption bands of a colored salt, 

 so-called, can be widened by the addi- 

 tion of suitable colorless salts as well 

 as by simple increase in concen- 

 tration. 



158. Cobalt Chloride in Acetone. 



Fig. 90, pi. 23, and fig. 94, pi. 24. 



Fig. 90 shows the changes in the posi- 

 tions of the centers of the regions 

 of absorption and transmission of 

 cobalt chloride produced by varying 

 the solvent. The depth of the cell 

 was 2.40 cm. Counting from the 

 comparison spectrum towards the 

 opposite side of the spectrogram, the 

 four photographic strips correspond 

 to solutions of anhydrous cobalt 

 chloride in water, in absolute methyl 

 alcohol, in absolute ethyl alcohol, and 

 in anhydrous acetone, respectively. 



The aqueous solution was rosy red. 

 The methyl solution was purple. 

 The color of the ethyl solution was 

 blue with a slight reddish tinge. The 

 solution in acetone was blue with a 



158. Cobalt Chloride in Acetone Cont'd. 



slight greenish tinge. The concen- 

 trations of the solutions, in the order 

 named, were, respectively, 0.325, 

 0.099, 0.097, and o.oio normal. 

 The aqueous solution absorbed prac- 

 tically all radiations from 0.20/x to 

 0.275/x. The blue-green band ab- 

 sorbed the region between 0.45/i and 



0.55/*- 



The solution having methyl alcohol for 

 solvent absorbed all of the ultra- 

 violet from 0.20/X to near 0.39/n. It 

 then transmitted from 0.39/1 to 

 0.495/i. The next absorption band 

 extended from 0.495/n to 0.56/x. The 

 faintness of the associated photo- 

 graphic strip shows the presence of 

 appreciable absorption in the yellow. 



Both the ultra-violet absorption and 

 the adjoining region of transmis- 

 sion were very nearly the same for 

 the solution in ethyl alcohol as for 

 that in methyl alcohol. On the con- 

 trary, the third strip gives no indi- 

 cation of return to transparency in 

 the yellow of the band which ab- 

 sorbed all of the green. 



The acetone solution transmitted the 

 region between about 0.38/^ and 

 0.56/1, but absorbed all the other 

 radiations which could aflfect the 

 Seed film. 



The phenomena in the visible spectrum 

 were brought out very clearly by 

 photographing with a Cramer 

 "Trichromatic" plate. The depth of 

 the cell was decreased to 2.00 cm. 



The aqueous solution transmitted 

 from beyond the shorter wave- 

 length end of the plate to 0.46/4 and 

 again from 0.543/t to beyond 0.625/t 

 at the other end of the plate. 



The solution in methyl alcohol trans- 

 mitted from 0.387/1 to o.495/t and 

 again from 0.548/1 to beyond 0.625/1. 

 The intensity of the transmitted 

 light, in the yellow and orange, how- 

 ever, was not as great for the 

 methyl as for the aqueous solution. 



The solution in ethyl alcohol only trans- 

 mitted from 0.385/1 to o.497/t. 



The solution in acetone only trans- 

 mitted from 0.373/1 to 0.560/1. 



*For exhaustive details see "Hydrates in Aqueous Solution," etc. Harry C. Jones, Publication No. 60 of the 

 Carnegie Institution of Washington. 



