| 摘要 |
1327543 Glass composition CORNING GLASS WORKS 12 Jan 1972 [21 Jan 1971] 1424/72 Heading C1M A crown glass comprises in percentage by weight 43-50 BaO; 15-23 SiO 2 ; 15-22 B 2 O 3 ; 5-10 ZnO; 0À1-5 CeO and 0À5-5 La 2 O 3 . The glass may also contain up to 10% total of Al 2 O 3 , Na 2 O, K 2 O, SrO, CuO, MgO, ZrO 2 , As 2 O 3 and Sb 2 O 3 . The glass has an ultra-violet cut, i.e. the wavelength limits within which must lie the wavelength at which the transmittance is 37%, is between 3500 Š and 3900 Š. The sharpness of cut i.e. the difference between the wavelengths where the transmittance is 15% and 60% is 150 Š when the cut is 3500 Š and 300 Š when the cut is 3900 Š. |
