COBALT CHLORIDE IN ACETONE. 249 



sion between 0.651/t and 0.634/. A strip of relatively weak transmission, 

 which, however, was much more intense than its less refrangible neighbor, 

 began at 0.634^ and had its middle at 6255. This was followed by two 

 comparatively narrow, symmetrical bands of almost complete absorption, 

 whose maxima had the wave-lengths 0.613/z and 0.6005/<. The middle of 

 the intervening and very faint band of transmission was at 0.607/*. The 

 spectrum for the 10 per cent solution was very much like that of the 8 

 per cent, the absorption bands, of course, being somewhat weaker. For 

 the 12 per cent solutions the bands were very faint indeed. The strongest 

 band had the approximate wave-length 0.700/<. The narrow bands at 

 0.613/x and 0.6005/< could only be seen by moving the spectrum across 

 the field of view. The 14 per cent solution showed only one absorption band. 

 This band was in the extreme red and was very weak. The 16 per cent 

 solution had no visible bands as such. The transmission from the bluish 

 color of 14 per cent, to the pinkish tinge of the 16 per cent solution, was due 

 to the gradual disappearance of the absorption bands in the red, and not to 

 an abrupt or continuous change of any kind whatsoever. The solution 

 having more than 16 per cent of water showed no absorption bands in the 

 spectroscope. 



Before taking up the discussion of the copper salts it is desirable to com- 

 pare the spectra of the mother-solutions of cobalt chloride with one another, 

 and to consider how much of the ultra-violet absorption was due to the 

 solvents themselves. [See plates 27 (a) and 27 (6).] Consider first the nega- 

 tive for 27 (6). The concentrations of the cobalt chloride in acetone, in ethyl 

 alcohol, in methyl alcohol, and in water were, respectively, 0.010,* 0.097, 0.099, 

 and 0.325.f The first solution was blue, with a slight greenish tinge. The 

 second solution was blue, with a slight reddish tinge. The second solution 

 was deeper blue than the first, due largely to the difference in concentra- 

 tion. The third and fourth solutions were, respectively, purple and red. The 

 photographic strips nearest to the numbered scale and to the comparison 

 spectrum correspond, respectively, to the solutions in acetone and in water. 

 The four steps are in the same order as that in w r hich the solutions are named 

 above. The depth of the cell was 2.40 cm. The strip pertaining to the 

 acetone solution recorded very faintly the intense doublet at 3330, but the 

 extreme limits of the continuous background were 0.370^ and 0.550/. The 

 strip corresponding to the ethyl alcohol solution gave the extreme limits 

 of transmission as 0.388^ and 0.496,. The negative strip pertaining to the 

 methyl alcohol solution gave the limits of one region of transmission as 

 0.3S5/* and 0.495/. Faint transmission was recorded from 0.555/t towards 



* Not the mother-solution for plate 26. 



t Diluted from the original mother-solution used in the preceding study of aqueous 

 solutions. 



