| 摘要 |
925,507. Coloured glass compositions. OWENS-ILLINOIS GLASS CO. Nov. 18, 1960, No. 39624/60. Class 56. An ultra-violet light absorbing green glass which gives good transmission of visible light comprises a soda-lime silica glass to which is added chromium oxide present in the glass in both the tri-valent and hexavelent state. The preferred composition is 60-75% (by weight) silica, 0.1-9.5% Al2O3, 6-12% CaO, 0-6% MgO, 0-1% BaO, 0-5% B2O3, 10-21% alkali metal oxides, less than 0-3% Fe2O3 and less than 0.3% total chromium oxides, present as both trivalent chromium oxide Cr2O3, and hexavalent chromium oxide Cr2O3, the latter ranging from 0.005 to 0.070%. Cobalt oxide in an amount 0.002-0.005% and copper oxide about 0.07% may be added to control the colour. KNO3 or NaNO3 may be employed as oxidizing agents to ensure the prescribed amount of hexavalent chromium is present in the glass. The batch is melted under carefully controlled oxidizing conditions which may be produced by the introduction of oxygen into the melt by means of an oxygen bubbler. Potassium or sodium dichromate and other chromates or chromites may be used to introduce chromium into the batch. U.S.A. Specification 2,974,052 is referred to. |
