2537. Margueritte, L. J. F. Nov. 12.
Materials. Relates to the manufacture of glass, crystal, enamels, glazings, and like vitreous compositions. Suitable proportions of the materials employed are given in the Specification. A transparent glass, free from potash and soda, is obtained by calcining a mixture of silica, lime, and alumina. Instead of employing pure materials, a clay may be used, to which pure materials may be added, as required, to obtain the desired relative proportions. It is stated that, by this method, with a clay of specified composition, a green-tinted glass is obtained, which might be used for making bottles, and that kaolin might be used for window glass, looking glass, &c. For making crystal, without potash, a mixture of silica, oxide of lead, lime and alumina is employed, the lime being substituted for the potash ordinarily used. Oxides of lead or zinc, &c. may also be added to this mixture. Felspar, which contains potash or soda, or both these alkalies, is also employed for the manufacture of glass, the proportion of alumina being reduced, if necessary, by the addition of silica and lime. The proportion of alkali may be increased, if desired. To produce a vitreous product which may be used for manufacturing crystal, the felspar may be calcined with metallic oxides, such as oxide of lead, the proportion of silica being increased by the addition of sand &c. The addition of other oxides, such as oxide of zinc or bismuth, produces a vitreous, fusible, translucent material. Other oxides may be added to tint the resulting product. Vitreous compounds are also obtained from phosphates, chiefly biphosphate of lime, although biphosphates of potash, soda, baryta, strontia, magnesia, alumina, lead, zinc, cobalt, &c. may be used. The biphosphates may be vitrefied alone, or in combination with alumina, silica, kaolin, clays, felspar, &c. The bisphosphate of lime in such combinations is stated to decompose salts, and acid or other elements which can be volatilized, while it also serves as a decolorizing agent for contained iron. By employing biphosphate of lime, cheap substitutes for minium may be used, e.g. sulphide or sulphate of lead or zinc, and the arsenio-sulphides of cobalt and nickel, and other natural minerals may be substituted forartificial oxides. Tinted products, suitable for coating colourless crystals, or as enamels, are obtained by the addition of the oxides of cobalt, chromium, copper, uranium, &c.
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