﻿and the Solvate Theory of Solution. 741 



is little short of proof. The only reasonable question is how 

 are we to interpret these facts ? Before attempting to answer 

 this question we should take into account, also the following- 

 fact. We have seen that a salt dissolved in a given solvent 

 is characterized by a definite absorption spectrum. When 

 a salt is dissolved in mixtures of varying proportions of two 

 solvents only two definite absorption spectra appear, one being 

 characteristic of: each solvent. One spectrum does not 

 gradually change into the other as the composition of the 

 mixed solvent changes, but only the relative intensities of 

 the two spectra vary. Starting with that mixture of the two 

 solvents in which both of the spectra are equally intense, if 

 we diminish the amount of a relative to b, the spectrum corre- 

 sponding to a becomes feebler and feebler, and the spectrum 

 corresponding to b more and more intense. This fact was 

 first noted by Jones and Anderson, and since repeatedly 

 confirmed by the work of Jones and Strong. We found 

 that when neodvmium chloride is dissolved in a mixture of 

 methyl alcohol and water, it showed a definite set of " water " 

 bands and a definite set of " methyl alcohol " bands. As the 

 amount of water in the solution was decreased relative to 

 the alcohol, the " water " bands decreased in intensity but 

 remained in the same position. As the amount of alcohol in 

 the solution was decreased relative to the water the " alcohol " 

 bands decreased in intensity, but their position remained 

 unchanged. 



Jones and Anderson interpreted these facts as strong 

 evidence in favour of the view that there are definite hydrates 

 and definite alcoholates in the solution. 



The spectroscopic evidence for solvation in solution furnished 

 by Jones and Anderson has, as has already been stated, been 

 increased many fold by the work of Jones and Strong. A 

 large number of solvents and a fairly large number of salts 

 have been used, and the existence of solvent bands in general 

 established. 



The question of the relative stability of the different solvates 

 with respect to various physical and chemical agents has been 

 studied at length by Jones and Strong by means of absorption 

 lines and bands. It would lead us beyond the scope of this 

 paper to discuss these results in detail. Suffice it to say that 

 the hydrates in general are the most persistent of all the 

 solvates, although this depends upon the conditions to which 

 the solution is subjected. 



Taking all of the spectroscopic work into account, I regard 

 the evidence from this source as strongly supporting the 

 solvate theory of solution as advanced in this laboratory more 



