The relationships between the structure and corrosion resistance of glasses with the nominal compositions xBaO-(100 - x)[yFe2O3-(1 - y)P2O5], where x = 0, 10, 20, and y = 30, 35, 40, are discussed. High performance liquid chromatography was used to characterize the phosphate anions that constitute the glass structure, and Mössbauer spectrometry was used to characterize the fractions and coordination environments of Fe2 + and Fe3 + ions in the glasses. Weight loss measurements in water were recorded and the most durable glasses were those with the smallest average phosphate anion sizes, independent of the relative BaO and Fe2O3 contents.