Electronic Polarisability of NaNO2–NaNO3 and NaOH–NaNO3 Ionic Melts and Effective Ionic Radius of OH－

Abstract

Abstract Molar volumes and refractive indexes of molten NaNO2–NaNO3 and NaOH–NaNO3 systems were measured by dilatometry and goniometry, respectively. The molar volumes of both systems increased with increasing temperature. Refractive indexes decreased with a rise of temperature or with increasing wavelength of the incident visible light. Assuming that the electronic polarisability is inherent in an ion, the electronic polarisability of a OH－ ion in the melt was estimated from the Lorentz–Lorenz equation to be 1.26×10−30 m3, being comparable with that in the crystal. The effective ionic radius of a OH－ ion was evaluated from the obtained electronic polarisability to be 1.34×10−10 m, using the correlation between the third power of the ionic radius and the electronic polarisability of an ion so far reported. The effective ionic radius obtained in this work was in good agreement with that assigned by Shannon.