38 ABSORPTION SPECTRA OF SOLUTIONS. 



The structure of the band differs materially in the different solvents, as 

 has been pointed out in the description of the spectrograms. With dilution 

 it narrows rapidly in methyl alcohol, slower in ethyl alcohol, and remains 

 constant or nearly so in acetone. That these changes can not be explained 

 by dissociation has already been pointed out by Jones and Uhler, who sug- 

 gested that they may be due to solvation. This is altogether reasonable, 

 and the behavior of the spectrum is exactly what we should expect from 

 the conclusions arrived at in the discussion of aqueous solutions. The 

 red absorption then was ascribed to "simple" hydrates, such as contain 

 2 or 3 molecules of water or less. It is not unlikely that " simple" solvates 

 of cobalt salts, in general, have this property of absorbing red light. 



We should expect the power to form solvates to be greater for methyl 

 alcohol than for ethyl alcohol, and greater for the latter than for acetone. 

 Hence, in case of ethyl alcohol and acetone at ordinary temperature, all 

 the solvates formed are perhaps simple enough to exert powerful red ab- 

 sorption, while with methyl alcohol this is only the case with concentrated 

 solutions or at elevated temperatures. The differences in the structure 

 of the band in the different solvents are, of course, to be expected, since 

 the "absorbers" are different. 



