Page:The American Cyclopædia (1879) Volume XVI.djvu/856

 826 ZINC ZINNIA The importations of Silesian spelter, which have averaged 3,400 tons per annum since 1862, amounted in 1875 to only 540 tons. The total annual product of zinc in Europe is over 150,000 tons, of which about half is produced in the German empire. Zinc White. The use of zinc oxide as a substitute for white lead was first suggested by Courtois, a manufac- turer of Dijon, near the close of the last cen- tury. M. Leclaire, a house painter of Paris, some years later devised a cheap method of producing it, by heating zinc in retorts and exposing the escaping vapors to a current of air, drawn by a chimney or exhausting fan through the condensing apparatus. He also prepared a drying oil suitable for its use, by boiling linseed oil with about 5 per cent, of oxide of manganese, and furthermore substi- tuted new yellow and green unchangeable pig- ments for the poisonous ones containing lead, copper, or arsenic. The chief, excellence of zinc white is its brilliant lustre and its free- dom from discoloration when exposed to sul- phuretted vapors, which turn lead paint black. Magnesia, or a mixture of the chloride and sulphate of zinc in small proportions, may be boiled in linseed oil, instead of manganese, to form a suitable drying oil. The Europeans still employ metallic zinc for this manufacture, and by selecting the purest spelter make the best varieties of zinc white. Such is the blanc de neige or "snow white" of the French, used by painters instead of "silver white." The ordinary zinc white, and " stone gray " and "gray oxide" of the English, are less pure. Stone gray is used as a ground color for walls, iron work, &c., and gray oxide for painting ships and as a ground color on stone or ce- ment. The manufacture of zinc white from natural oxide or oxidized ores can only be practised with pure materials and a smokeless fuel. The following outline of the process as carried on at the Lehigh works. Bethlehem, Pa., will suffice as an example. The ores used for this purpose (20 per cent, zinc) are mixed with 50 per cent, pea or dust coal, rolled, and screened; and the fine and coarse ores are treated separately though similarly. The fur- naces are single or double reverberatories, in which the charge is placed on heavy rolled- iron grates, with perforations for the passage of air. The charge is, for the single furnaces (5 ft. by 3), 240 Ibs. of ore, 120 Ibs. of anthra- cite, and 100 Ibs. of pea coal as a bed ; for the double ores (16 ft. by 5), 640 Ibs. of ore, 820 Ibs. of coal, 240 Ibs. of pea coal. No fluxes are added, the object being to keep the charge from becoming impervious to the blast, which is furnished by four fan blowers. The process lasts four hours for each charge. A workman tends four furnaces, cleaning and charging one each hour. The chemical reactions give a cu- rious instance of the performance of reduc- tion and oxidation in the same furnace at the same time. The blast first oxidizes the lowest coal to carbonic acid, which, passing upward through the bed of coal, is reduced to carbonic oxide. This reduces the zincic oxide of the ore to metallic zinc, becoming itself carbonic acid again. The zinc volatilizes at the high temperature resulting ; and its heated vapors, uniting with the carbonic acid, are again oxi- dized. The oxide thus formed is carried along a conducting channel over a sheet of water into a cooling tower, 75 ft. high and 80 ft. in circumference at the base. Much of the damp, impure oxide settles in this tower ; the remain- der is conveyed down another tower, 50 ft. high, and by an exhaust fan is forced through another channel, or cooling chamber floored with sheet zinc, on which another portion of impure oxide collects. The remainder is car- ried forward by the draft into the bag room, where a large number of muslin bags, 30 ft. long, are suspended vertically from the sheet- iron tubes conveying the oxide. Through these bags the air and gases of the draft leak out, while the flocculent zinc-white powder is retained. The bags are shaken every four hours, and the oxide is removed. By a similar method the red oxide ores of New Jersey are manufactured into zinc white ; and a few years ago a considerable amount of so-called Bart- lett oxide, containing both zinc and lead, and highly recommended for paint, was manufac- tured from the ore of a mine in North Caro- lina, which consisted of an intimate mixture of galena and zinc blende, in fortunately suit- able proportions. The mine is at present idle (1876), and the product, under that name, is no longer in market ; but it is said that galena is now sometimes mixed with zinc ores, to pro- duce an oxide superior to white lead for vul- canizing rubber and for painting surfaces ex- posed to the weather. Zinc white is often mixed with barytes or white lead; and besides its use as paint, it has been applied as a mastic for metallic joints, as glazing for pottery, as enamel for papers and cardboards in place of lead or barium carbonate, and as an ingre- dient in artificial gems and glass instead of lead or other metallic oxides. ZINGARELLI, Nieold, an Italian composer,, born in Kome, April 4, 1752, died in Naples, May 5, 1837. He composed the opera of Mon- tezuma in 1781, followed by numerous other operas for Italian theatres, and produced his Antigone unsuccessfully in Paris in 1789. He became musical director of the chapel of the Vatican in 1804, in 1813 director of the new conservatory in Naples, and in 1816 musical director at the cathedral. He composed about 16 operas, besides many cantatas and oratorios, and a variety of church music. ZINGIS KHAN. See GENGHIS KHAN. ZINNIA (named after J. G. Zinn, a German botanist), a genus of plants of the composite family, of which there are about 12 species, belonging to the Mexican flora, though some occur along our southern boundary, and a few are sufficiently ornamental to be popular gar- den plants. They are mostly annuals, with