| 摘要 |
462,304. Glass manufacture. KODAK, Ltd. (Eastman Kodak, Co.) Sept. 3, 1935, No. 24579. Drawings to Specification. [Class 56] Optical glasses having a high refractive index and a low dispersion are made from batches containing a low proportion of silica but a high percentage, preferably more than 50 per cent, of one or more of the oxides of metals in the even series of Groups III, IV, and V of the periodic system having an atomic weight greater than 47. The preferred oxides are those of titanium, zirconium, lanthanum tantalum, and thorium. Tungsten oxide also is suitable, and the oxides of yttrium, columbium, and hafnium may be used. Boric oxide may be used as a flux, and small amounts of alkali metals may be included. Preferably, silica is not included, or not more than 10 per cent is used. Examples of suitable batches are given in the Specification.
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