| 摘要 |
PROBLEM TO BE SOLVED: To profitably produce a lead-free optical barium flint glass having good meltability and processability, very high chemical resistance, a refractive index nd of 1.55-1.66 and an Abbes's numberηd of 39-52. SOLUTION: The glass is a compsn. consisting of, by weight on the oxide basis, 40-60% SiO2 , 6.5-12% B2 O3 , 10-35% BaO, 0-1% CaO, 0-2% ZnO, 5-12% TiO2 , 0.5-3.5% Al2 O3 , 3-7.5% Na2 O and 3-8% K2 O (Na2 O+K2 O <=15%) and optionally contg. a usual amt. of a refining agent. The glass exhibits positive abnormal or normal partial dispersion in the blue region of its spectrum.
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