| 摘要 |
649,512. Glass manufacture. KODAK, Ltd. Jan. 29, 1947, No. 2807. Convention date, Jan. 29. 1946. Addition to 649,511. Drawings to Specification. [Class 56] The batch of an optical glass whose predominant elements are P, O, F, Al and Ba and in which the atomic ratio F/P is not less than 0.23 (e.g. lies between 1 and 6.5), may also contain: alkali fluoride to an amount less than 7 per cent by wt. and less. by mol. per cent, than the barium fluoride content; BeF 2 less than 12 per cent by wt.; SiO 2 0-27 per cent by wt.; Mg, Ca, Zn, Sr, La and Th may also be present. Ranges and specific examples are given of glasses containing BaF 2 and Al(PO 3 ) 3 in binary, ternary and more complex systems, and nD, and ugF values are quoted in some cases; the batches melt at 1050‹C. or less. A glass particularly resistant to HF comprises (wt. per cent):-MgF 2 0.5. CaF 2 0.5. ZnF 3 1.0, SrF 2 0.5, BaF 2 31.0, LaF, 0.5, ThF, 47.0, Al(PO 3 ) 3 19.0. Specification 462,304 is referred to. The Specification as open to inspection under Sect. 91 comprises also batches containing Cd and Pb. This subject-matter does not appear in the Specification as accepted.
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