| 摘要 |
725,206. Glass. ZEISS-STIFTUNG, C. [trading as JENAER GLASWERK SCHOTT & GEN.], April 27, 1953 [May 9, 1952], No. 11530/53. Class 56 An optical glass with a refractive index of at least 1.68 and free from thoria and beryllia contains (percentage parts by weight) B 2 O 3 36-50. ZrO 2 up to 11, La 2 O 3 26-44 and CaO 5-19 but not more CaO than 33 minus one half the La 2 O 3 . Part or all of the CaO over 5 per cent. may be replaced by St, Mg, Ba, Zn or Cd oxides not exceeding a combined total of 6 per cent., or by Li 2 O up to 2 per cent. Ta 2 O 5 and/or Nb 2 O 5 up to a total of 9 per cent. may be present and Al 2 O 3 , SiO 2 , In 2 O 3 , GeO 2 and WO, up to a total of 4 per cent. may also be added.
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