70 Studies on Solution. 



spectrum for the cases of certain solutions. These points have been 

 spoken of by Houstoun 1 as "sensitive points." These sensitive points 

 have been found in general to be situated at the edges of absorption 

 bands. 



At present there is no adequate theory to explain the facts which 

 have been recorded here. The fact that A varies with the concen- 

 tration has been probably correctly attributed by Jones and Anderson 

 and others to the formation of complexes, which were considered to 

 be loose chemical compounds of molecules of the salt with molecules 

 of the solvent. Undoubtedly the changes in A with c observed in this 

 investigation may be explained in a qualitative manner by the hypothe- 

 sis of complexes, or "solvates" as they have been called; but before it 

 can be useful for the interpretation of quantitative data, the solvate 

 hypothesis must be couched in more mathematical terms. 



. Roy. Soc. Edinburgh, 33, 151 (1912-13). 



