Effect of composition and other factors on the specific refraction and dispersion of glasses

Seven of the better known specific-refraction ratios were examined for their comparative appl,icability to glass. It is shown by a comprehensive statistical treatment of available data (including many new data) that, of these ratios, only the Gladstone-Dale possesses to a satisfactory degree each of the following desirable features: (1) It varies linearly with chemical composition and with the square of the wave number of the incident light; (2) fo r a given composition and wavelength of light, it is substantially the same for both the vitreous and crystalline states; and (3) for the vitreous state, it is independent of thermal history. Gladstone-Dale factors for 47 oxides as constituents of glass (and corresponding factors derived from nonglassy substances) are given. These factors are shown to be related to the periodicity of the elements. Specific dispersion factors, useful for computing the dispersion index, or v-value, of a glass are given for 32 oxides.