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    • 10. 发明专利
    • DE924484C
    • 1955-03-03
    • DEK0006245
    • 1950-09-08
    • KENT-JONES DOUGLAS WILLIAMARTHUR JAMES AMOS
    • KENT-JONES DOUGLAS WILLIAMMARTIN WILLIAM
    • G01N21/47G01N33/10H01K1/54
    • 581,453. Electric incandescent lamps. PHILIPS LAMPS, Ltd., MARTIN, S. L., and BEVINGTON, C. F. P. June 14, 1944, No. 11370. [Class 39 (ii)] In order to prevent corrosion of the tungsten filament of an electric incandescent lamp when calcium fluoride is incorporated in the getter mixture for the purpose of preventing blackening of the bulb, the calcium fluoride is supplemented by a small quantity of silica or similar refractory oxide such as beryllia, alumina or titania, which is readily attacked by hydrogen fluoride and forms comparatively innocuous compounds which do not corrode the filament. Either synthetic or mineral calcium fluoride may be used and mixed mechanically with not less than 0.2 per cent. by weight of the refractory oxide, the preferred quantity being about 3 per cent. Since synthetic calcium fluoride is liable to absorb water and liberate hydrogen fluoride when the salt is hydrolysed as a result of heating, it is preferably sintered, then treated with concentrated hydrochloric acid and washed with distilled water, after which it is milled with finely ground refractory oxide, e.g., quartz, and then treated with concentrated hydrochloric acid to which a small amount of nitric acid has been added. If mineral calcium fluoride of not less than 98 per cent. purity is employed, the preliminary purification and sintering may, be dispensed with.