| 摘要 |
512,292. Glass manufacture. VEREINIGTE GLUHLAMPEN UND ELEKTRIZITATS AKT.- GES. Oct. 3, 1938, No. 28655. Convention date, Oct. 2, 1937. [Class 56] A method of facilitating the melting of glass batches, particularly those which are fusible with difficulty, consists in precipitating some or all of the constituents together from solution instead of mixing them as powders. The method can be used for making glass composed of Si O2, Al2 O3, and B2 O3, such as 64 per cent. of Si O2, 8 per cent of Al2 O3, and 28 per cent. of B2 O3, or a glass containing 83 per cent. Si O2, 4.5 per cent. Al2 O3, and 12 per cent. B2 O3. The silica is preferably precipitated from the aqueous solution of a silicon compound, e.g., waterglass, and aluminium hydroxide is precipitated together with the colloidal silica by introducing a suitable aluminium compound into the waterglass. The gel mixture is washed and filtered, and a calculated quantity of boric acid, dissolved in water, is stirred in with the: gel and then evaporated to dryness. Other constituents, such as alkalies, can be added also to the gel mixture. The,dried gels may be voluminous, and in this case the mixture may be compressed by mechanical means to reduce occluded air. Preferably the mixture is kept below the sintering temperature for some time to allow absorbed water to escape. |
