paints when containing about 45 per cent of precipitated barium carbonate produce a velvety finish. Witherite (natural barium carbonate) can not be used for this purpose and should not be confused with precipitated barium carbonate. It is also used as the raw material for making barium peroxide and in the manufacture of some kinds of enameled iron ware.

Barium chloride is a white barium salt which is fairly soluble in water. It crystallizes with two molecules of water and is usually sold in the crystalline or powdered form. It is largely used in the manufacture of blanc fixe and of color lakes as a mordant for fixing acid dyes on the inert base, such as aluminum hydroxide or blanc fixe. Barium chloride is also used in the purification of salt, as a water softener, a chemical reagent in sulphur determinations, to some extent in the ceramics industry, and in the manufacture of certain photographic chemicals. It has certain medicinal uses.

Barium nitrate is a soluble barium salt used principally for making barium peroxide or dioxide. It is also used in pyrotechnics for making green fire and green signal lights and in the manufacture of certain explosive mixtures, thus giving barium nitrate some military significance. It also has certain medicinal uses similar to barium chloride.

Barium monoxide or baryta has its chief use as an intermediate product in the preparation of the binoxide or peroxide of barium. It is also used in the manufacture of certain varieties of optical glass. In European countries, especially Germany, it is used in refining beet sugar.

Barium hydroxide, hydrate of baryta, or caustic baryta, has very little commercial use in the United States. During the period of high prices for caustic potash, barium hydroxide was used to convert sulphate of potash into caustic potash. In Europe it is used with barium monoxide in the refining of beet sugar.

Barium binoxide, barium dioxide, or barium peroxide, is used chiefly for the manufacture of hydrogen peroxide. It is also used for the production of oxygen and as a bleach, especially in the blanket and straw hat industries. Large quantities of hydrogen peroxide were required for war purposes. This demand and the use of barium peroxide in tracer bullets resulted in a large increase in production.

Barium sulphide is the intermediate barium compound from which the majority of the other barium chemicals are made and is one of the necessary materials in the manufacture of lithopone. It is also used with lime as a depilatory in leather manufacture. Crude barium sulphide, which is made by roasting barytes with coal, is known as "black-ash."

Barium chromate or lemon yellow, or yellow ultramarine, is used as a yellow pigment.

Barium chlorate is used in pyrotechnics and in dyeing.

DOMESTIC PRODUCTION.

Production and consumption.-Prior to the war the United States was almost wholly dependent on imports for its supply of barium chemicals. There was practically no domestic production of the barium salts such as barium dioxide, chloride, nitrate, and blanc fixe. The only product manufactured in this country on a large scale prior to the war, which utilized barytes as a raw material, was lithopone, which is discussed on pages 53-60.

The shutting off of imports with the outbreak of the war gave a great stimulus to the establishment of a barium chemical industry in the United States. In addition there were large war demands for certain barium salts (barium peroxide, blanc fixe, and barium nitrate) which greatly increased the domestic production and tended to develop an industry in the United States. Plants for the manufacture of barium salts have been located chiefly in the eastern and southern sections of the United States. The southern plants are located in close proximity to the raw material barytes. There are also plants located in Ohio and Illinois. The following is a list of the principal manufacturers of barium chemicals in the United States:

Alton Chemical Corporation, Alton, Ill.

Chicago Copper & Chemical Co., 111 West Jackson Boulevard, Chicago, Ill. Consolidated Chemical Products Co., Alton, Ill.

Durex Chemical Corporation, 320 Fifth Avenue, New York City. (Plant at Sweetwater, Tenn.)

E. I. du Pont de Nemours & Co., Wilmington, Del.

J-H-R. Products Co., Willoughby, Ohio.

Oakland Chemical Co., 10 Astor Place, New York City.

Rollin Chemical Corporation, 120 Broadway, New York City. (Plant at Charleston, W. Va.)

The production of barium chemicals has increased steadily from 17,646,000 pounds in 1915 to 46,372,000 pounds in 1918. Preliminary figures furnished by the Geological Survey indicate a total production of barium chemicals during 1919 of about 41,500,000 pounds. The order of the barium salts according to quantity of production during 1918 was blanc fixe, barium carbonate, and barium chloride. Table 18 shows the domestic output of barium chemicals, beginning with 1915.

TABLE 18.-Production of barium chemicals in the United States, 1915-1918. [From Mineral Resources, United States Geological Survey.]

Process of manufacture.-Barytes is the raw material used in the United States for the manufacture of barium chemicals with the exception of a small quantity of witherite which is imported. A deposit of witherite was discovered in California in 1914, but it has not proved to be of commercial importance.

The manufacturers of barium chemicals prefer to use the washed, high-grade barytes of the soft type, but they can and do use the barytes which could not be used in the preparation of the highest grades of ground barytes. The crude barytes is first crushed and mixed with the proper proportions of pulverized coal. The proportion of barytes and coal varies slightly with individual manufacturers; it is generally one part of coal to four parts of barytes by weight. This mixture is roasted for about four hours in a rotating reduction furnace. The barium sulphate is reduced by the coal to barium sulphide during the roasting. The crude barium sulphide (black ash), which contains about 70 per cent of barium sulphide, is then treated with hot water and a solution of barium sulphide is thereby formed. This solution is used as the starting point for the preparation of the barium chemicals and also in the manufacture of lithopone. (See p. 54.)

Barium carbonate is precipitated from a solution of barium sulphide by treatment with sodium carbonate (soda ash). Sodium sulphide is obtained as a by-product. It can also be prepared by passing a current of carbon dioxide gas through the solution of barium sulphide. By this last process, sodium sulphide is not obtained as a by-product.

The method of producing blanc fixe or precipitated barium sulphate depends on the physical properties which are desired for the finished product. It was formerly made only by treating a solution of barium chloride with sodium sulphate or sulphuric acid. It is now usually made by precipitation from a solution of barium sulphide by means of salt cake (sodium sulphate). This method produces a much denser product than that produced from barium chloride, and in addition yields sodium sulphide as a valuable

FIGURE 3.-DIAGRAM OF THE MANUFACTURE OF BARIUM CHEMICALS.
-RAW-INTERMEDIATE -OR FINISHED PRODUCTS. ---APPARATUS OR STEPS IN PROCESS.

concentrated solutions, thus giving a crystalline product which is a valuable base for the manufacture of very brilliant colors.

Barium chloride may be produced by treating witherite (barium carbonate) with hydrochloric acid. It is usually produced in this country directly from crude barytes by roasting with coal and calcium chloride. It may also be prepared by treating a solution of barium sulphide with calcium chloride.

by-product. It is also made as a by-product of the manufacture of hydrogen peroxide when barium peroxide is treated with sulphuric acid. For certain color purposes blanc fixe is precipitated from hot,

Barium nitrate is produced by adding sodium nitrate (Chile saltpeter) either to a solution of barium chloride or to a solution of barium sulphide. It is also produced by dissolving witherite in a solution of nitric acid. The barium nitrate thus produced can be converted into barium oxide, dioxide, or hydroxide.

Barium chromate is prepared by treating a solution of barium chloride or other soluble barium salts with sodium chromate.

Barium peroxide or dioxide is prepared from either barium nitrate or barium carbonate. The barium nitrate or carbonate is first converted into barium oxide by heating in a closed apparatus. The barium oxide is then converted into barium peroxide by heating at about 700° C. in a current of air free from carbon dioxide and moisture.

Whenever a sodium salt is added to a solution of barium sulphide in the preparation of barium salts there is produced, in addition to the desired barium product, sodium sulphide as a valuable byproduct. This is an important product of the barium chemical industry, and has a large consumption by the American dye industry in the preparation of sulphur colors, especially sulphur black, which is used in large quantities.

FOREIGN PRODUCTION.

Although statistics are not available on the production of barium chemicals in foreign countries, it is undoubtedly true that Germany was the largest single producer prior to the war. England, France, and Italy possessed smaller barium chemical industries, and the industries in these countries have also been stimulated by war conditions which prevented exports of barium products from Germany. Table 19, which shows Germany's exports and imports of barium chemicals, indicates the importance of the German industry prior to the war.

TABLE 19.-Germany's exports and imports of barium chemicals.
[From Vierteljahrshefte zur Statistik des Deutschen Reichs.]