The present situation as to tile effect of the medium on electronic and vibrationM spectra is typical of a field which is at t ract ing a rapidly increasing body of interest. In the case of electronic spectra a very promising approach appears to be tha t by KOSOWER (1), who proposed the use of the transition energ'ies corresponding to some appropiate chargetransfer bands as an empirical measure of solvent polari ty; these Iransition energies (designated as Z-values) are linear functions of the Winstein-Griinwald ]2-value,whi('h is a kinetic measure of the ionizing power of the medium. In the case of vibrational spe(.ira, concerned with our present measurements, the theorelieal t reatments up to present proposed (2) are essentially foeuse4 on tile ewduat.ion of ~he extent of electrostatic solute-solvent interactions; tim first equation to be deduced, that by Kirkwood-Bauer-Magat (KBM),