| 摘要 |
857,182. Optical glass compositions. ZEISSSTIFTUNG, C., [trading as JENAER GLASWERK SCHOTT & GEN.]. Aug. 25, 1959 [Aug. 26, 1958], No. 29086/59. Drawings to Specification. Class 56. A thorium-free optical glass which consists of B 2 O 3 and La 2 O 3 and Ta 2 O 5 and/or ZrO 2 wherein the contents are in the following ranges by weight percentage: B 2 O 3 20-40; LazOs (44-0À04 (ZrO 2 )<SP>2</SP>)-60 ; TazOs 0-31 and ZrO 2 0-12, the combined Ta 2 O 5 and ZrO 2 being at least 4 and wherein the La 2 O 3 is further limited according to the following Table I, and the Ta 2 O 5 being determined according to the desired refraction nd of the glass according to the following Table II, the values in each case being interpolable graphically. Preferably the La 2 O 3 content is not less than and the ZrOz content is as high as possible. The oxides are melted in a platinum crucible between 1300 and 1400‹C., the melt refined at about 20‹C. higher and cooled with stirring to between 1000 and 1100‹C., poured into a steel mould, and allowed to cool slowly. A number of particular examples of compositions are given.
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