CRYSTAL GLASS HAVING REFRACTIVE INDEX HIGHER THAN 1,53 WITHOUT A CONTENT OF COMPOUNDS OF LEAD, BARIUM AND ARSENIC

摘要

This invention relates to a crystal glass having a refractive index higher than 1.53 and a high mechanical strength, free of any content of compounds of lead, barium and arsenic and guaranteeing maximum safety for health, which consists in that it comprises by weight: 55 - 70% SiO2, 0,05 - 3,5% Li2O, 2 - 15% Na2O, more than 3% and less than 5 % or more than 15 % and less than 19% K2O, 5 to 10% CaO, more than 1% and less than 4 % or more than 7 % and less than 8% ZnO, 0.1 - 3.5% B2O3, 0.1 - 3.5% Al2O3, 0.1 - 3.5% TiO2, less than 3.5% ZrO2, 0.05 - 1.5% Gd2O,3 0.05 - 1% P2O5, 0.1 - 1 % Sb2O3,