THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



i Y 1916. /C 



L. Light Absorption and Fluorescen\.—^IY. ^l&fyxnge in 

 Absolution with Concentration. By E. C. 0. Baly, M.Sc 7 

 F.R.S., Grant Professor of Inorganic Chemistry in the 

 University of Liverpool, and F. G. Tryhorn, M.Sc* 



IN the previous papers of this series the relation between 

 the frequencies of the absorption and fluorescence bands 

 in the ultra-violet and infra-red regions has been dealt 

 with f- Since the absorption spectra of the majority of 

 compounds can only be observed when they are in solution, 

 it becomes necessary to discuss the changes in absorption 

 that are produced by the solvent in order to determine 

 whether the relationships established for the vapour spectra 

 of substances are perfectly general. In the present paper 

 it is proposed to deal with the change in the position of an 

 absorption band and the change in absorptive power pro- 

 duced by a solvent, and to show how such variations are 

 due to the nature of the solvent and to the concentration. 



In the first place, the change in the position of the ab- 

 sorption band with concentration may be dealt with. In 

 Table I. are given the positions of the centre of the absorption 

 band of pyridine solutions at given concentrations, the 

 solvent being C0 2 -free water. In the first column are given 

 the volumes in litres in which one gram-molecule of pyridine 

 (79 orams) is dissolved, while the second and third columns 



* Communicated by the Authors. 



t Phil. Mag. xxvii. p. 632 (1914) ; xxix. p. 223, xxx. p. 510 (1915). 



Phil. Mag. S. 6. Vol. 31. No. 185. May 1916. 2 F 



