﻿[ 730 ] 



LXIX. Ahsorption Spectra and the Solvate Theory of 

 Solution. By Harry 0. Jones * 



[These investigations on the Absorption Spectra of Solutions were 

 carried out with the aid of Grants from the Carnegie Institution of 

 Washington.] 



A DOZEN f or more independent lines of evidence have 

 been discovered, all pointing to the conclusion that dis- 

 solved substances combine with more or less of the solvent. 

 In a word, in dealing with solutions we must take into 

 account not only the dissociation of the dissolved substance, 

 but also its solvation, or power to combine with the solvent. 



With this idea in mind it seemed highly desirable to study 

 the absorption spectra of solutions. The absorption of light 

 by dissolved substances is a resonance phenomenon; those 

 wave-lengths that are absorbed finding something in the 

 solution which they can throw into resonance with themselves. 

 If the dissolved substance combines with more or less of the 

 solvent, it seems reasonable to suppose that the substance 

 would show different resonance from thnt which it would 

 manifest in the uncombined condition. This conclusion is 

 independent of whether the absorption of light by a dissolved 

 subtances is due to molecules, ions, or electrons. 



It seemed that some knowledge might be gained in indi- 

 vidual cases as to whether there was solvation, and if so, what 

 was its order of magnitude, by studying the power of solu- 

 tions to absorb light under changing conditions of dilution, 

 temperature, &c. 



This was, in general, the thought that led us to take up, six 

 years ago, the problem of the absorption spectra of solutions 

 in as broad a way as possible; and the work has been in 

 progress continuously since that time, under Grants generously 

 awarded by the Carnegie Institution of Washington. We 

 have had at our disposal in this work Eowland concave 

 gratings ruled by Dr. Anderson, which gave us the large 

 dispersion necessary to separate properly the absorption lines 

 and bands. 



The absorption spectra of somewhat more than 6000 

 solutions have been photographed, and some conclusions 

 reached whose bearing on the solvate theory are of interest 

 and we hope of some importance. 



For details concerning the methods of work and the 



* Communicated by the Author. 



t Zeitschr. phr/s. Chem. lxxiv. p. 325 (1910) ; Amer. Chem. Journ. 

 xli. p. -36 (1900)'. 



