Chemical Properties
Barium sulfate is available as white powder or polymorphous crystals. It is stable, odor-
less, insoluble, or negligibly soluble in water, and may produce sulfur oxides on burning.
It occurs naturally as mineral barite (barytes). It has wide use as an inert i ller pigment extender in paints, primers, inks, plastics, l oor tiles, paper coatings, polymer i bers, and
rubber. It is used as the semi-transparent base (lake) for organic pigments and as a thixo-
tropic weighting mud in oil well drilling. Barium sulfate is radio-opaque and is used as bar-
ium meal in medical x-ray diagnosis. Barium sulfate is a contrast agent that is used to help
x-ray diagnosis of problems in areas of the upper GI tract, like the esophagus, the stomach,
and/or the small intestine. Barium sulfate is the raw material for the manufacture of litho-
pone, a white pigment, and is used in the manufacture of photographic paper, wallpaper,
and glassmaking; in battery plate expanders; and in heavy concrete for radiation shield.
Definition
ChEBI: A metal sulfate with formula BaO4S. Virtually insoluble in water at room temperature, it is mostly used as a component in oil well drilling fluid it occurs naturally as the mineral barite.
Brand name
Baricon (Mallinckrodt); Bar-test (Glenwood);
Barocat (Mallinckrodt); Barosperse (Mallinckrodt); Barosperse
II (Mallinckrodt); Barotrast (Rhone-Poulenc
Rorer); Epi-C (Mallinckrodt); Epi-Stat 57 (Mallinckrodt);
Epi-Stat 61 (Mallinckrodt); Esophotrast (Rhone-Poulenc Rorer); Oratrast (Rhone-Poulenc Rorer).
General Description
White or yellowish odorless powder or small crystals. Mp: 1580°C (with decomposition). Density: 4.25-4.5 g cm-3. Insoluble in water, dilute acids, alcohol. Soluble in hot concentrated sulfuric acid. Used as a weighting mud in oil-drilling, in paints, paper coatings, linoleum, textiles, rubber. Administered internally (barium cocktail) as a radio-opaque diagnostic aid.
Reactivity Profile
BARIUM SULFATE is non-combustible and non-toxic. Emits toxic sulfur oxides when heated to decomposition. Can act as an oxidizing agent, but usually does not. Reacts with reducing agents such as potassium, phosphorus or aluminum (heating with aluminum can cause an explosion).
Health Hazard
Exposures to barium sulfate cause irritation to the eyes, lachrimation; redness, scaling, and
itching are characteristics of skin inl ammation. Although barium sulfate has been identi-
i ed as a non-toxic dust, long-term inhalation of dust in high concentrations has caused
benign pneumoconiosis (baritosis), deposition of dust in the lungs in sufi cient quantities
to produce adverse effects. This produces a radiological picture even though symptoms
and abnormal signs may not be present. The Fumes of barium are respiratory irritants and
over-exposure to dusts and fumes is known to cause rhinitis, frontal headache, wheezing,
laryngeal spasm, salivation, and anorexia. Long-term effects include nervous disorders
and adverse effects on the heart, circulatory system, and musculature. Heavy exposures to
barium sulfate may cause benign pneumoconi in exposed workers. However, there are no
reports indicating that barium sulfate has potential occupational hazards or carcinogenicity.
Potential Exposure
Barium sulfate is used as an opaque
medium in radiography; as a mud weighting material in oil
well drilling; in paper coating; as a paint pigment.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth method if victim
ingested or inhaled the substance; give artificial respiration
with the aid of a pocket mask equipped with a one-way valve
or other proper respiratory medical device. Administer oxygen
if breathing is difficult. Remove and isolate contaminated
clothing and shoes. In case of contact with substance,
immediately flush skin or eyes with running water for at
least 20 minutes. For minor skin contact, avoid spreading
material on unaffected skin. Keep victim warm and quiet.
Effects of exposure (inhalation, ingestion, or skin contact) to
substance may be delayed. Ensure that medical personnel
are aware of the material(s) involved and take precautions to
Barium Sulfate 357
protect themselves. Medical observation is recommended
for 24 to 48 hours after breathing overexposure, as pulmonary
edema may be delayed. As first aid for pulmonary
edema, a doctor or authorized paramedic may consider
administering a drug or other inhalation therapy.
Shipping
UN1564 Barium compounds, n.o.s., Hazard
Class: 6.1; Labels: 6.1—Poisonous materials.
Incompatibilities
May act as an oxidizer. Reacts with
reducing agents such as hydrides, potassium, phosphorus or
aluminum. Aluminum powder1heat may be violent; possibly
explosive.
Physical properties
Barium sulfate has the molecular formula of BaSO4
and the molecular weight of 233.3896 g/mol. It can be
prepared by the reaction of barium carbonate and
sulfuric acid:
BaCO3+H2SO4?BaSO4+CO2+H2O
Barium sulfate is a soft crystalline solid. It is
a rhombic crystal. The pure salt is white but the color
of the mineral “barite” can vary between red, yellow,
gray or green, depending on impurities. Its density is
4.50 g/cm3 and its refractive index is 1.64. It melts
around 1580°C but decomposes above 1600°C. Its
hardness is 4.3 to 4.6 Mohs. It is virtually insoluble in
water (285 mg/l at 30°C) and insoluble in alcohol. Its
Ksp is 1.1×10-10. It is soluble in concentrated sulfuric
acid. The crystal structure of BaSO4 is known to be rhombic, with a space group pnma. The lattice parameters are: a=8.896? , b=5.462°, c=7.171 ?,
V=348.4 ?3.
Silica is the prime impurity that can be removed as
sodium fluorosilicate by treatment with hydrofluoric
acid followed by caustic soda. Very pure barium sulfate
may be obtained by treating an aqueous solution of
a soluble barium salt with sodium sulfate:
BaCl2+Na2SO4?BaSO4+2NaCl
Barium sulfate is one of the most insoluble salts of the
alkaline earths. It does not undergo double decomposition
reactions in aqueous phase like its Mg homologue.
It dissolves in concentrated H2SO4 to form an acid
sulfate that breaks down to BaSO4 upon dilution. Reduction
with coke under heating produces barium sulfide:
BaSO4+3C?BaS+2CO+CO2
Occurrence
Barium sulfate is widely distributed in nature and occurs as the mineral barite (also known as barytes or heavy spar). It often is associated with other metallic ores, such as fluorspar. Barites containing over 94% BaSO4 can be processed economically.
Barium sulfate has many commercial applications. It is used as natural barite, or precipitated BaSO4. The precipitated salt in combination with equimolar amount of co-precipitated zinc sulfide formerly was used as a white protective coating pigment, known as lithophone. Similarly, in combination with sodium sulfide, it is used to produce fine pigment particles of uniform size, known as blanc fixe. Natural barite, however, has greater commercial application than the precipitated salt. It is used as drilling mud in oil drilling to lubricate and cool the drilling bit, and to plaster the walls of the drill hole to prevent caving. It is used as a filler in automotive paints, plastics and rubber products. It also is used in polyurethane foam floor mats; white sidewall rubber tires; and as a flux and additive to glass to increase the refractive index.
Other chemical applications of barium sulfate are as the opaque ingredient in a barium meal for x-ray diagnosis; as a pigment for photographic paper; and to prepare many barium salts.
Production Methods
Natural barium sulfate or barite is widely distributed in nature. It also contains silica, ferric oxide and fluoride impurities. Silica is the prime impurity which may be removed as sodium fluorosilicate by treatment with hydrofluoric acid followed by caustic soda.
Very pure barium sulfate may be precipitated by treating an aqueous solution of a barium salt with sodium sulfate:
BaCl2 + Na2SO4 → BaSO4 + 2NaCl
Precipitated BaSO4 is often used in many industrial applications. Blanc fixe and Lithopone are made by the reactions of barium sulfide with sodium sulfate and zinc sulfate, respectively.
Pharmaceutical Applications
Barium salts can be highly toxic even at low concentrations. Barium carbonate is highly toxic and can be used as rat poison as it readily dissolves in the stomach acid. Barium sulfate is the least toxic barium compound mainly because of its insolubility. Barium sulfate is used in a variety of applications ranging from white paint to X-ray contrast agent. The clinical use of barium sulfate suspension is well known under the term barium meal. Patients are given a suspension of barium sulfate to swallow. Using X-ray imaging, the whole oesophagus, the stomach and the intestines can be visualised. Barium sulfate lines the tissue whilst travelling through the digestive tract. The heavy barium ions absorb X-rays readily and therefore these structures become visible in an X-ray screening. Barium sulfate is a well-used and tolerated oral radio-contrast agent. It is also used as radio-contrast agent in enemas.
