Optical basicity: A review

Over several decades, extensive research has been devoted to developing the optical basicity concept to quantify Lewis basicity of oxidic media. Spectroscopy (ultraviolet (UV), infrared (IR), and fluorescence) was originally used to experimentally determine optical basicity, but linear refractive index and x-ray photoelectron spectroscopy (XPS) have been more recent techniques for determining basicity of glasses. While glasses have been one media of study, slags, oxyanion melts, and molten halide salts are also of interest. The concept has been only briefly explored in molten salts, but optical basicity could be a valuable tool for assessing its corrosivity. This review summarizes different techniques used to determine optical basicity, their pitfalls, and the preliminary work outlined for molten salts.