Raman Spectral Studies of Alkaline Solutions of Germanium Dioxide

Abstract

Raman frequencies, polarizations, and infrared frequencies of nearly saturated aqueous solutions of KOH containing various amounts of GeO₂ (0.5 to 6.0 mole liter⁻¹) have been obtained at 25°C, and relative integrated Raman intensities of bands of the alkaline solutions at 529, 667, and 765 cm⁻¹ were also obtained for various stoichiometric GeO₂ molarities, CGeO₂, under conditions of nearly constant, and of varying stoichiometric KOH molarity, C_KOH. In the concentration ranges 0<CGeO₂M, and 10.53<C_KOHM, the relative integrated Raman intensity of the 765‐cm⁻¹ band, I₇₆₅, was observed to be nearly proportional to CGeO₂, which suggests that much of the germanium is present in one form, e.g., as H₂GeO₄^2—. However, marked downward deviations from proportionality observed for another intensity of H₂GeO₄^2—, I₆₆₇, evident in the range ∼2<CGeO₂M, indicate that appreciable concentrations of a second species, e.g., Ge₂O₅^2—, must contribute to the 765‐cm⁻¹ band intensity to produce the observed near proportionality. The species Ge₂O₅^2— is also thought to give rise to another band at 529 cm⁻¹, the intensity of which increases from very low to measurable values in the range 0<CGeO₂M, and the presence of more than one germanium‐containing species is given additional support by polarization data. Raman and infrared frequencies of solid Na₂GeO₃ and of vitreous GeO₂, and infrared frequencies of hexagonal GeO₂, also obtained in this work, are included, as are viscosity and electrical conductivity data for alkaline solutions of germanium dioxide.