Page 130 - Chemical and process design handbook

Speight_Part II_B 11/7/01 3:11 PM Page 2.71

BARIUM SULFATE

o
Barium sulfate (BaSO , melting point 1580 C with decomposition) occurs
4
as colorless rhombic crystals. It is soluble in concentrated sulfuric acid,
forming an acid sulfate; dilution with water reprecipitates barium sulfate.
Precipitated barium sulfate, known as blanc fixe, is prepared from the reac-
tion of aqueous solutions of barium sulfide (BaS) and sodium sulfate
(Na SO ).
2 4
Barium sulfate, often prepared by grinding the ore barite, is not usually
used alone as a white pigment because of its poor covering power, but is
widely used as a pigment extender. It also contributes to gloss. Its princi-
pal use (over 90 percent) is in oil-drilling muds. Blanc fixe is made by pre-
cipitation of a soluble barium compound, such as barium sulfide or barium
chloride, by a sulfate. This form has finer particles than the ground barite
and is often used in printing inks to impart transparency.

See also Barium Salts, Lithopone.

2.71