| 摘要 |
620,892. Glass compositions. KODAK, Ltd. Jan. 29, 1947, No. 2809. Convention date, Jan. 29, 1946. Drawings to Specification. [Class 56] Glass is formed from a batch consisting substantially of TiO 2 3-12 per cent, PbO 66-96 per cent, and B 2 O 3 2-30 per cent. The glasses are hard and durable against moisture attack and have a high refractive index and di-electric constant and a low abbe value, and may be used as optical material, high di-electric substances or gem stones. Small amounts of other components may be added to increase the chemical durability and to minimize devitrification. A preferred batch contains PbO 78 per cent, TiO 2 12 per cent and B 2 O 3 10 per cent, and the resultant glass has a refractive index of 2.0685 and abbe value 17.7. Pb 3 O 4 , PbO or Pb(MO 3 ) 2 may be used as the lead ingredient, and H 3 BO 3 as the source of B 2 O 3 , and the mixture is heated in a 96 per cent silica crucible at 1300' C. for 5-7 minutes, or at 1000‹C. for 30 minutes; shaken and poured into moulds heated to 350‹C. The glass is slightly yellow and the colour increases with the lead content. A high TiO 2 content increases the resistance to moisture. A little SiO 2 may be absorbed from the crucible. Compositions are also given in mols per cent and illustrated in ternary diagram.
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