THE LITHOPONE INDUSTRY. DESCRIPTION AND USES. Lithopone (incorrectly spelled lithophone) is a white pigment which consists of a mixture of approximately 70 per cent barium sulphate and 30 per cent of zinc calculated as zinc sulphide. The zinc is present in lithopone as 26 to 28 per cent of zinc sulphide and 1 to 3 per cent of zinc oxide, according to conditions of manufacture. The lithopone produced in this country by all manufacturers is a standard product of approximately the composition given above, which is about in proportion to the chemical equivalents of barium sulphate and zinc sulphide. In Europe lithopone is commonly sold in grades containing more or less zinc sulphide than the standard of 30 per cent. For example, the following grades of lithopone are sold on the German market: Gelbsiegel (yellow seal), 11 to 18 per cent zinc sulphide; Blausiegel (blue seal), 22 to 30 per cent zinc sulphide; Grünsiegel (green seal), 32 to 42 per cent zinc sulphide. Lithopone is known commercially under various brand names in addition to the general name of lithopone. The trade names used by various manufacturers, with the exception of the Sherwin-Williams Co., of Cleveland, Ohio, which firm markets their product simply as lithopone, are as follows: Beckton White, E. I. du Pont de Nemours & Co., Wilmington, Del. Marbon White, Mineral Refining & Chemical Corporation, St. Louis, Mo. Sterling White, Midland Chemical Co., Chicago, Ill. Lithopone is used extensively as a white pigment in flat and enamel wall paints for interior use. The chief competitors of lithopone as a pigment are white lead, zinc oxide, and leaded zinc oxide. It is also used in large quantities as an inert filler in rubber goods, paper, linoleum, oilcloth, and in window-shade cloth. As a rule lithopone is not extensively used in outside paints because of the property of darkening when exposed to sunlight. In recent years there have been placed on the market brands of lithopone which are said to withstand exposure to sunlight. 53 DOMESTIC PRODUCTION. Raw materials.-The basic raw materials necessary for the manufacture of lithopone are crude barytes, coal or coke, zinc, and sulphuric acid. Other chemicals are required in the process of manu facture, but in minor quantities. Large quantities of clear, soft water are required in making up the solutions of materials and in the washing of the lithopone to remove soluble impurities. Of these materials, this report is especially concerned with crude barytes. The other basic raw materials are available from domestic sources, and, with the exception of zinc, present no special tariff problem. The barytes requirements of lithopone manufacturers prior to the war were supplied wholly by imports, chiefly from Germany. The entire lithopone industry was then located along the Atlantic coast, at or within a short distance of tidewater. Under these conditions crude barytes could be imported at a cost of about $5.20 per short ton, delivered at plant, which was less than the price at which domestic barytes could be purchased. The stoppage of imports of crude barytes from Germany as a result of war conditions forced the lithopone manufacturers to seek a domestic supply. This condition and the establishment of a barium chemical industry was responsible for the domestic development of crude barytes production in the southern district, as previously described. (See p. 21.) It is reasonably certain, with restoration of normal competitive conditions and under existing tariff duties (15 per cent ad valorem) on crude barytes, that lithopone manufacturers located along the Atlantic coast will return to imports as the source of their barytes requirements. Regardless of a duty, the lithopone manufacturers located in the Middle West will use chiefly crude barytes from the Missouri district. The relation of the cost of crude barytes to the total cost of manufacturing lithopone is shown on page 87. From this it is possible to calculate the effect of an increase or decrease in the cost of crude barytes on the cost of lithopone, other factors remaining fixed. Process of manufacture.-The manufacture of lithopone requires the preliminary production of a solution of barium sulphide and a solution of zinc sulphate. The preparation of barium sulphide by roasting barytes with coal has already been described. (See p. 44.) The zinc sulphate solution is prepared by dissolving some form of zinc (zinc ash, scrap, skimmings, spelter, or roasted ore) in dilute sulphuric acid. Since the zinc materials used contain, as a rule, other metals as impurities (chiefly iron, copper, or cadmium), which would form colored products on treatment with barium sulphide, it is necessary to purify thoroughly the zinc sulphate solution. Various chemicals are used at this point for purification of the zinc FIGURE 4.-DIAGRAM OF THE MANUFACTURE Solid lines. -Raw, intermediate, or finished products sulphate solution, which is one of the most important steps in the manufacture and requires careful chemical control. Crude lithopone is now precipitated from the purified zinc sulphate solution as a white insoluble substance by adding a hot solution of barium sulphide. The crude lithopone is filtered from the solution, then dried, and calcined in a muffle furnace at about 500° C., which may or may not utilize waste heat from the roasting of the barytes with coal. The hot product from the furnace is thrown into water ("quenching "), ground in pulp, washed several times with water to remove soluble impurities, filtered, and dried. The dry lithopone is run through a disintegrator, which breaks it up into a fine powder, and it is then packed in bags or barrels for shipment. In some cases the lithopone is air floated to insure a uniformly fine product before packing. The process of manufacturing lithopone is shown graphically in Figure 4. Production and consumption.-The production of lithopone in the United States has shown a rapid growth during the last 10 years. From 1910 to 1919 the production increased nearly sixfold, or from 25,330,000 pounds to about 145,000,000 pounds. During this period the domestic output of lithopone has supplied from 84 to 100 per cent of the total consumption. There has been relatively little competition from imported lithopone. The growth of the lithopone industry can be attributed to the increased utilization of this commodity and the natural growth of the consuming industries during the last 10 years. Although exports of lithopone are not shown separately in Commerce and Navigation, it is known that a fairly large export trade has developed in lithopone during 1920. Table 23 shows the figures for the production, importation, and consumption of lithopone in this country from 1910 to 1919, inclusive. Figure 5 shows graphically the relation of imports and production of lithopone to the total consumption in the United States. TABLE 23.-Production and consumption of lithopone in the United States. 1 1910 to 1918, inclusive, from Mineral Resources, U. S. Geological Survey. 1919 from reports submitted to the Tariff Commission by individual manufacturers. 2 From 1910 to Oct. 3, 1913, listed as "white sulphide of zinc." |