Page 129 - Chemical and process design handbook

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BARIUM SALTS

The most common naturally occurring barium compounds are the mineral
carbonate (witherite, BaCO ) and the sulfate (barite, BaSO ).
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The manufacture of soluble barium salts involves treatment of the min-
eral (usually barite) with the relevant acid, filtration to remove insoluble
impurities, and crystallization of the salt.
The high-temperature reduction of barium sulfate with coke yields the
water-soluble barium sulfide (BaS), which is subsequently leached out.
Treatment of barium sulfide with the relevant chemical yields the desired
barium salt. Purification of the product is complicated by the impurities
introduced in the coke. Pure barium carbonate and barium sulfate are made
by precipitation from solutions of water-soluble barium salts.
Barite is ground, acid-washed, and dried to produce a cheap pigment or
paper or rubber filler, or changed to blanc fixe.
The applications of barium compounds are varied and include use as
oil-drilling mud. Barium carbonate is sometimes employed as a neutral-
izing agent for sulfuric acid and, because both barium carbonate and bar-
ium sulfate are insoluble, no contaminating barium ions are introduced.
The foregoing application is found in the synthetic dyestuff industry.
Barium carbonate is used in the glass industry and in the brick and clay
industry. When barium carbonate is added to the clay used in making
bricks, it immobilizes the calcium sulfate and prevents it from migrating to
the surface of the bricks and producing a whitish surface discoloration.
Barium sulfate is a useful white pigment, particularly in the precipitated
form, blanc fixe. It is used as a filler for paper, rubber, linoleum, and oil-
cloth. Because of its opacity to x-rays, barium sulfate, in a purified form,
is important in contour photographs of the digestive tract.
The paint industry is the largest single consumer of barium compounds.
Barium sulfide and zinc sulfate solutions are mixed to give a precipitate of
barium sulfate and zinc sulfide, which is heat treated to yield the pigment
lithopone. Barium chlorate and nitrate are used in pyrotechnics to impart a
green flame. Barium chloride is applied where a soluble barium compound
is needed.

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