Identifiers | |||
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3D model (JSmol) | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
DrugBank | |||
ECHA InfoCard | 100.028.896 | ||
EC Number |
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KEGG | |||
PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 1564 | ||
CompTox Dashboard (EPA) | |||
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Properties | |||
BaSO4 | |||
Molar mass | 233.39 g/mol | ||
Appearance | white crystalline | ||
Odor | odorless | ||
Density | 4.49 g/cm3 | ||
Melting point | 1,580 °C (2,880 °F; 1,850 K) | ||
Boiling point | 1,600 °C (2,910 °F; 1,870 K) (decomposes) | ||
0.2448 mg/100 mL (20 °C) 0.285 mg/100 mL (30 °C) | |||
Solubility product (Ksp) | 1.0842 × 10−10 (25 °C) | ||
Solubility | insoluble in alcohol, [1] soluble in concentrated, hot sulfuric acid | ||
−71.3·10−6 cm3/mol | |||
Refractive index (nD) | 1.636 (alpha) | ||
Structure | |||
orthorhombic | |||
Thermochemistry | |||
Heat capacity (C) | 101.7 J/(mol K) | ||
Std molar entropy (S⦵298) | 132 J/(mol·K) [2] | ||
Std enthalpy of formation (ΔfH⦵298) | −1465 kJ/mol [2] | ||
Pharmacology | |||
V08BA01 ( WHO ) | |||
by mouth, rectal | |||
Pharmacokinetics: | |||
negligible by mouth | |||
rectal | |||
Legal status |
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Hazards | |||
GHS labelling: | |||
P260, P264, P270, P273, P314, P501 | |||
NFPA 704 (fire diamond) | |||
Flash point | noncombustible [3] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp) [3] | ||
REL (Recommended) | TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) [3] | ||
IDLH (Immediate danger) | N.D. [3] | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of barium and materials prepared from it. Its opaque white appearance and its high density are exploited in its main applications. [4]
About 80% of the world's barium sulfate production, mostly purified mineral, is consumed as a component of oil well drilling fluid. It increases the density of the fluid, [5] increasing the hydrostatic pressure in the well and reducing the chance of a blowout.
Barium sulfate in suspension is often used medically as a radiocontrast agent for X-ray imaging and other diagnostic procedures. It is most often used in imaging of the GI tract during what is colloquially known as a "barium meal". It is administered orally, or by enema, as a suspension of fine particles in a thick milk-like solution (often with sweetening and flavoring agents added). Although barium is a heavy metal, and its water-soluble compounds are often highly toxic, the low solubility of barium sulfate protects the patient from absorbing harmful amounts of the metal. Barium sulfate is also readily removed from the body, unlike Thorotrast, which it replaced. Due to the relatively high atomic number (Z = 56) of barium, its compounds absorb X-rays more strongly than compounds derived from lighter nuclei.
The majority of synthetic barium sulfate is used as a component of white pigment for paints. In oil paint, barium sulfate is almost transparent[ citation needed ], and is used as a filler or to modify consistency. One major manufacturer of artists' oil paint sells "permanent white" that contains a mixture of titanium white pigment (TiO2) and barium sulfate. The combination of barium sulfate and zinc sulfide (ZnS) is the inorganic pigment called lithopone. In photography it is used as a coating for certain photographic papers. [5] It is also used as a coating to diffuse light evenly.
Barium sulfate is highly reflective, of both visible and ultraviolet light. [6] Researchers used it as an ingredient in paint that reflects 98.1% of solar radiation, allowing surfaces to which it has been applied to stay cooler in sunlit conditions. Commercially available white paints only reflect 80 - 90% of solar radiation. [7] By using hexagonal nanoplatelet boron nitride, the thickness of a coat of this type of paint was reduced to 0.15 mm. [6]
A thin layer of barium sulfate called baryta is first coated on the base surface of most photographic paper to increase the reflectiveness of the image, with the first such paper introduced in 1884 in Germany. [8] The light-sensitive silver halide emulsion is then coated over the baryta layer. The baryta coating limits the penetration of the emulsion into the fibers of the paper and makes the emulsion more even, resulting in more uniform blacks. [9] Further coatings may then be present for fixing and protection of the image. Baryta has also been used to brighten papers intended for ink-jet printing. [10]
Barium sulfate is commonly used as a filler for plastics to increase the density of the polymer in vibrational mass damping applications. In polypropylene and polystyrene plastics, it is used as a filler in proportions up to 70%. It has an effect of increasing acid and alkali resistance and opacity. Such composites are also used as X-ray shielding materials due to their enhanced radio-opacity. [11] In cases where machinability and weight are a concern, composites with high mass fraction (70–80%) of barium sulfate may be preferred to the more commonly used steel shields. [12]
Barium sulfate is used in soil testing. Tests for soil pH and other qualities of soil use colored indicators, and small particles (usually clay) from the soil can cloud the test mixture and make it hard to see the color of the indicator. Barium sulfate added to the mixture binds with these particles, making them heavier so they fall to the bottom, leaving a clearer solution.
In colorimetry, barium sulfate is used as a near-perfect diffuser when measuring light sources.
In metal casting, the moulds used are often coated with barium sulfate in order to prevent the molten metal from bonding with the mould.
It is also used in brake linings, anacoustic foams, powder coatings, and root canal filling.
Barium sulfate is an ingredient in the "rubber" pellets used by Chilean police. [13] This together with silica helps the pellet attain a 96.5 Shore A hardness. [13]
Barium sulfate is used as a catalyst support when selectively hydrogenating functional groups that are sensitive to overreduction. With a low surface area, the contact time of the substrate with the catalyst is shorter and thus selectivity is achieved. Palladium on barium sulfate is also used as a catalyst in the Rosenmund reduction.
As barium compounds emit a characteristic green light when heated at high temperature, barium salts are often used in green pyrotechnic formulas, although nitrate and chlorate salts are more common. Barium sulfate is commonly used as a component of "strobe" pyrotechnic compositions.
As barium sulfate has a high melting point and is insoluble in water, it is used as a release material in casting of copper anode plates. The anode plates are cast in copper molds, so to avoid the direct contact of the liquid copper with the solid copper mold, a suspension of fine barium sulfate powder in water is used as a coating on the mold surface. Thus, when the molten copper solidifies in form of an anode plate it can be easily released from its mold.
Barium sulfate is sometimes used, besides polytetrafluoroethylene (PTFE), to coat the interior of integrating spheres due to the high reflectance of the material and near Lambertian characteristics.
Barium sulfate is listed among the materials acceptable to the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) for the manufacturing of firearms and/or components that are made of plastic, to achieve compliance with the U.S. federal requirement that an X-ray machine must be able to accurately depict the shape of the plastic firearm or component. [14]
Almost all of the barium consumed commercially is obtained from barite, which is often highly impure. Barite is processed by thermo-chemical sulfate reduction (TSR), also known as carbothermal reduction (heating with coke) to give barium sulfide:
In contrast to barium sulfate, barium sulfide is soluble in water and readily converted to the oxide, carbonate, and halides. To produce highly pure barium sulfate, the sulfide or chloride is treated with sulfuric acid or sulfate salts:
Barium sulfate produced in this way is often called blanc fixe, which is French for "permanent white". Blanc fixe is the form of barium encountered in consumer products, such as paints. [5]
In the laboratory barium sulfate is generated by combining solutions of barium ions and sulfate salts. Because barium sulfate is the least toxic salt of barium due to its insolubility, wastes containing barium salts are sometimes treated with sodium sulfate to immobilize (detoxify) the barium. Barium sulfate is one of the most insoluble salts of sulfate. Its low solubility is exploited in qualitative inorganic analysis as a test for Ba2+ ions, as well as for sulfate.
Untreated raw materials such as natural baryte formed under hydrothermal conditions may contain many impurities, a.o., quartz, or even amorphous silica. [15]
Barium sulfate is reduced to barium sulfide by carbon. The accidental discovery of this conversion many centuries ago led to the discovery of the first synthetic phosphor. [4] The sulfide, unlike the sulfate, is water-soluble.
During the early part of the 20th century, during the Japanese colonization period, hokutolite was found to exist naturally in the Beitou hot-springs area near Taipei City, Taiwan. Hokutolite is a radioactive mineral composed mostly of PbSO4 and BaSO4, but also containing traces of uranium, thorium and radium. The Japanese harvested these elements for industrial uses, and also developed dozens of “therapeutic hot-spring baths” in the area. [16]
Although soluble salts of barium are moderately toxic to humans, barium sulfate is nontoxic due to its insolubility. The most common means of inadvertent barium poisoning arises from the consumption of soluble barium salts mislabeled as BaSO4. In the Celobar incident (Brazil, 2003), nine patients died from improperly prepared radiocontrast agent. In regards to occupational exposures, the Occupational Safety and Health Administration set a permissible exposure limit at 15 mg/m3, while the National Institute for Occupational Safety and Health has a recommended exposure limit at 10 mg/m3. For respiratory exposures, both agencies have set an occupational exposure limit at 5 mg/m3. [17]
Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (BaSO4). Baryte is generally white or colorless, and is the main source of the element barium. The baryte group consists of baryte, celestine (strontium sulfate), anglesite (lead sulfate), and anhydrite (calcium sulfate). Baryte and celestine form a solid solution (Ba,Sr)SO4.
Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula FeSO4·xH2O. These compounds exist most commonly as the heptahydrate (x = 7) but several values for x are known. The hydrated form is used medically to treat or prevent iron deficiency, and also for industrial applications. Known since ancient times as copperas and as green vitriol (vitriol is an archaic name for sulfate), the blue-green heptahydrate (hydrate with 7 molecules of water) is the most common form of this material. All the iron(II) sulfates dissolve in water to give the same aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry and is paramagnetic. The name copperas dates from times when the copper(II) sulfate was known as blue copperas, and perhaps in analogy, iron(II) and zinc sulfate were known respectively as green and white copperas.
Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It is an ionic compound consisting of the ions copper(II) Cu2+
, carbonate CO2−
3, and hydroxide OH−
.
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide.
Lead(II) sulfate (PbSO4) is a white solid, which appears white in microcrystalline form. It is also known as fast white, milk white, sulfuric acid lead salt or anglesite.
Barium hydroxide is a chemical compound with the chemical formula Ba(OH)2. The monohydrate (x = 1), known as baryta or baryta-water, is one of the principal compounds of barium. This white granular monohydrate is the usual commercial form.
Barium carbonate is the inorganic compound with the formula BaCO3. Like most alkaline earth metal carbonates, it is a white salt that is poorly soluble in water. It occurs as the mineral known as witherite. In a commercial sense, it is one of the most important barium compounds.
Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is a white powder, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting to the dihydrate BaCl2·2H2O, which are colourless crystals with a bitter salty taste. It has limited use in the laboratory and industry.
Cadmium sulfate is the name of a series of related inorganic compounds with the formula CdSO4·xH2O. The most common form is the monohydrate CdSO4·H2O, but two other forms are known CdSO4·8⁄3H2O and the anhydrous salt (CdSO4). All salts are colourless and highly soluble in water.
Barium nitrate is the inorganic compound with the chemical formula Ba(NO3)2. It, like most barium salts, is colorless, toxic, and water-soluble. It burns with a green flame and is an oxidizer; the compound is commonly used in pyrotechnics.
Lithopone, C.I. Pigment White 5, is a mixture of inorganic compounds, widely used as a white pigment powder. It is composed of a mixture of barium sulfate and zinc sulfide. These insoluble compounds blend well with organic compounds and confer opacity. It was made popular by the cheap production costs, greater coverage. Related white pigments include titanium dioxide, zinc oxide, zinc sulfide, and white lead.
Chrome yellow is a bright, warm yellow pigment that has been used in art, fashion, and industry. It is the premier orange pigment for many applications.
Scheele's Green, also called Schloss Green, is chemically a cupric hydrogen arsenite, CuHAsO
3. It is chemically related to Paris Green. Scheele's Green was invented in 1775 by Carl Wilhelm Scheele. By the end of the 19th century, it had virtually replaced the older green pigments based on copper carbonate. It is a yellowish-green pigment commonly used during the early to mid-19th century in paints as well as being directly incorporated into a variety of products as a colorant. It began to fall out of favor after the 1860s because of its toxicity and the instability of its color in the presence of sulfides and various chemical pollutants. The acutely toxic nature of Scheele's green as well as other arsenic-containing green pigments such as Paris Green may have contributed to the sharp decline in the popularity of the color green in late Victorian society. By the dawn of the 20th century, Scheele's green had completely fallen out of use as a pigment but was still in use as an insecticide into the 1930s. At least two modern reproductions of Scheele's green hue with modern non-toxic pigments have been made, with similar but non-identical color coordinates: one with hex#3c7a18 and another with hex#478800. The latter is the more typically reported color coordinate for Scheele's green.
Aluminium nitrate is a white, water-soluble salt of aluminium and nitric acid, most commonly existing as the crystalline hydrate, aluminium nitrate nonahydrate, Al(NO3)3·9H2O.
Barium sulfide is the inorganic compound with the formula BaS. BaS is the barium compound produced on the largest scale. It is an important precursor to other barium compounds including BaCO3 and the pigment lithopone, ZnS/BaSO4. Like other chalcogenides of the alkaline earth metals, BaS is a short wavelength emitter for electronic displays. It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.
Strontium carbonate (SrCO3) is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite.
Barium bromide is the chemical compound with the formula BaBr2. It is ionic and hygroscopic in nature.
Zirconium(IV) sulfate is the name for a family of inorganic salts with the formula Zr(SO4)2(H2O)n where n = 0, 4, 5, 7. These species are related by the degree of hydration. They are white or colourless solids that are soluble in water.