Magneto optical rotatory dispersion studies of simple electrolyte solutions. Part 2.—Measurements on solutions of NaBr, KBr, NaI and KI

Abstract

The m.o.r.d. of concentrated aqueous solutions of NaBr, KBr, NaI and KI were measured in the wavelength region 350–600 nm. The variation of the specific rotations of the solutions with concentration of solute could be interpreted in terms of the competing processes of solvent structure-making and structure-breaking. The changes in rotation with wavelength were fitted to a non-term Drude equation and the constants of this equation, K and λ₀, claculated by the Biot–Lowry, the Yang–Doty and the Heller methods. It was evident, however, that λ₀ could not be identified with the peak position of an absorption band and that the Drude equation is merely a convenient empirical relationship for the m.o.r.d. results in the wavelength range studied. The variation of K with solute concentration was compatible with the relative effects of cations and anions on solvent structure. The magnetic rotations due to the solutes were calculated in three different ways and were related to the known properties of the solutes.