Glasses can be considered to be solutions, rather than chemical compounds. According to Meyer-Arendt, about 95% of all glasses are of the "soda-lime" type, containing silicon dioxide (silica), Na2O (soda), and CaO (lime). Crown glass is a soda-lime-silica composite. Flint glasses contain 45-65% lead oxide - they are high-density, high-dispersion, high-refractive-index glasses. There are glasses which have barium oxide rather than lead oxide; they are called barium glasses. Barium glasses have refractive indices comparable to the flints, but have lower dispersions.