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'{{short description|Inorganic compound}} {{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 476997146 | ImageFile = Barium-sulfate-2D.png | ImageSize = 225px | ImageName = Chemical structure of barium sulfate | ImageFileL2 = Barite-unit-cell-3D-vdW.png | ImageNameL2 = 3D model of barium sulfate | ImageFileR2 = Bariumsulfatpulver.png | IUPACName = | OtherNames = |Section1={{Chembox Identifiers | Abbreviations = | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 25BB7EKE2E | ChEMBL_Ref = {{ebicite|changed|EBI}} | ChEMBL = 2105897 | InChIKey = TZCXTZWJZNENPQ-NUQVWONBAD | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = TZCXTZWJZNENPQ-UHFFFAOYSA-L | CASNo = 7727-43-7 | CASNo_Ref = {{cascite|correct|CAS}} | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID =22823 | EINECS = 231-784-4 | PubChem = 24414 | SMILES = [Ba+2].[O-]S([O-])(=O)=O | InChI = 1/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 | RTECS = CR060000 | MeSHName = | ChEBI_Ref = {{ebicite|changed|EBI}} | ChEBI = 133326 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = D02052 | DrugBank = DB11150 | UNNumber = 1564 }} |Section2={{Chembox Properties | Formula = BaSO₄ | MolarMass = 233.38 g/mol | Appearance = white crystalline | Odor = odorless | Density = 4.49 g/cm³ | MeltingPtC = 1580 | MeltingPt_notes = | BoilingPtC = 1600 | BoilingPt_notes = (decomposes) | Solubility = 0.2448&nbsp;mg/100&nbsp;mL (20&nbsp;°C) <br> 0.285&nbsp;mg/100&nbsp;mL (30&nbsp;°C) | SolubilityProduct = 1.0842 × 10⁻¹⁰ (25&nbsp;°C) | SolubleOther = insoluble in [[ethanol|alcohol]],<ref>{{cite book | title = CRC Handbook of Chemistry and Physics | publisher = CRC Press | year = 2004 | edition = 85th | pages = [https://archive.org/details/crchandbookofche81lide/page/4 4–45] | isbn = 0-8493-0485-7 | url-access = registration | url = https://archive.org/details/crchandbookofche81lide/page/4 }}</ref> soluble in concentrated, hot [[sulfuric acid]] | Solvent = | pKa = | pKb = | RefractIndex = 1.636 (alpha) | MagSus = −71.3·10⁻⁶ cm³/mol }} |Section3={{Chembox Structure | CrystalStruct = orthorhombic }} |Section5={{Chembox Thermochemistry | DeltaHf = −1465&nbsp;kJ/mol<ref name="Zumdahl, Steven S. 2009">{{cite book |author = Zumdahl, Steven S. |title=Chemical Principles |edition=6th |publisher=Houghton Mifflin Company |year=2009 |isbn=978-0-618-94690-7}}</ref> | Entropy = 132&nbsp;J/(mol·K)<ref name="Zumdahl, Steven S. 2009"/> }} |Section6={{Chembox Pharmacology | ATCCode_prefix = V08 | ATCCode_suffix = BA01 | AdminRoutes = by mouth, rectal | Bioavail = negligible by mouth | Metabolism = | HalfLife = | ProteinBound = | Excretion = rectal | Legal_status = | Legal_US = Rx only | Legal_UK = | Legal_AU = | Legal_CA = | Pregnancy_category = | Pregnancy_AU = }} |Section7={{Chembox Hazards | PPhrases = {{P-phrases|260|264|270|273|314|501}} | MainHazards = | NFPA-H = 0 | NFPA-F = 0 | NFPA-R = 0 | NFPA-S = | RPhrases = | SPhrases = | RSPhrases = | FlashPt = noncombustible | FlashPt_notes=<ref name=PGCH/> | AutoignitionPt = | ExploLimits = | PEL = TWA 15 mg/m³ (total) TWA 5 mg/m³ (resp)<ref name=PGCH>{{PGCH|0047}}</ref> | REL = TWA 10 mg/m³ (total) TWA 5 mg/m³ (resp)<ref name=PGCH/> | IDLH = N.D.<ref name=PGCH/> }} }} '''Barium sulfate''' (or '''sulphate''') is the [[inorganic compound]] with the chemical formula [[Barium|Ba]][[Sulfate|SO₄]]. It is a white crystalline solid that is odorless and [[Solubility|insoluble]] in [[water]]. It occurs as the mineral [[barite]], which is the main commercial source of [[barium]] and materials prepared from it. The white opaque appearance and its high density are exploited in its main applications.<ref name=Holleman>Holleman, A. F. and Wiberg, E. (2001) ''Inorganic Chemistry'', San Diego, CA : Academic Press, {{ISBN|0-12-352651-5}}.</ref> ==Uses== ===Drilling fluids=== 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,<ref name="Ullmann">Robert Kresse, Ulrich Baudis, Paul Jäger, H. Hermann Riechers, Heinz Wagner, Jochen Winkler, Hans Uwe Wolf, "Barium and Barium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2007 Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a03_325.pub2}}</ref> increasing the hydrostatic pressure in the well and reducing the chance of a [[Blowout (well drilling)|blowout]]. ===Radiocontrast agent=== {{Main|Barium sulfate suspension}} [[Barium sulfate suspension|Barium sulfate in suspension]] is frequently used medically as a [[radiocontrast]] agent for [[X-ray]] [[Medical imaging|imaging]] and other diagnostic procedures. It is most often used in imaging of the [[Gastrointestinal tract|GI tract]] during what is colloquially known as a "[[barium meal]]". It is administered orally, or by [[enema]], as a [[Barium sulfate suspension|suspension]] of fine particles in a thick milk-like solution (often with sweetening and flavoring agents added). Although barium is a [[Heavy metals|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. ===Pigment=== 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|date=December 2020}}, 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 ([[titanium dioxide|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.<ref name=Ullmann/> ===Heat-reflecting paint=== In 2021, researchers at Purdue University announced that they had formulated a paint using barium sulfate which reflects 98.1% of all solar radiation, thus cooling surfaces to which it has been applied. This contrasts with commercially available white paints which can only reflect 80 - 90%  of the sunlight that hits such painted surfaces, thus causing them to get warmer.  The researchers have partnered with a company to scale up the paint and put it on the market, and a patent for this paint has been applied for now. 1. WO2020072818 - METAL-FREE SOLAR-REFLECTIVE INFRARED-EMISSIVE PAINTS AND METHODS OF PRODUCING THE SAME   <nowiki>https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2020072818&tab=PCTBIBLIO&_ga=2.82536342.1803355587.1618177710-1869368167.1598324459</nowiki><ref name="PurduePaint">[https://www.purdue.edu/newsroom/releases/2021/Q3/purdue-record-for-the-whitest-paint-appears-in-latest-edition-of-guinness-world-records.html Purdue record for the whitest paint appears in latest edition of 'Guinness World Records'], by Kayla Wiles, at [[Purdue University]]; published September 16, 2021; retrieved October 18, 2021</ref> ===Paper brightener=== 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]].<ref name='getty-sg'>The Getty Conservation Institute, ''Silver Gelatin. The Atlas of Analytical Signatures of Photographic Processes''. J. Paul Getty Trust, 2013.</ref> 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.<ref>Salvaggio, ''Nanette L. Basic Photographic Materials and Processes.'' Taylor & Francis US, Oct 27, 2008. p. 362.</ref> (Further coatings may then be present for fixing and protection of the image.) More recently, baryta has been used to brighten papers intended for [[ink-jet printing]].<ref>Nikitas, Theano. "Inkjet papers that will give your photos pizzazz: are you and your clients bored with your photo prints? check out our favorite fine-art and specialty inkjet papers that are sure to make your images stand out." Photo District News July 2012: 36+. General Reference Center GOLD. Web. 3 Nov. 2012.</ref> ===Plastics filler=== 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 enhanched radio-opacity.<ref>{{cite journal |last1=Lopresti |first1=Mattia |last2=Alberto |first2=Gabriele |last3=Cantamessa |first3=Simone |last4=Cantino |first4=Giorgio |last5=Conterosito |first5=Eleonora |last6=Palin |first6=Luca |last7=Milanesio |first7=Marco |title=Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study |journal=International Journal of Molecular Sciences |date=28 January 2020 |volume=21 |issue=3 |pages=833 |doi=10.3390/ijms21030833 |pmid=32012889 |pmc=7037949 |doi-access=free }}</ref> For some particular applications, composites with high mass fraction (70–80%) of barium sulfate may be preferred to the more commonly used steel shields.{{Clarify|date=June 2021|Please, explain why, because radiation shielding performance only depends on the density of the materials and on the thickness of the absorber! If a special application is considered, it should be clearly mentioned here also!}}{{Citation needed|date=June 2021}} ===Niche uses=== 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 (optics)|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 lining]]s, [[anechoic|anacoustic]] foams, [[powder coating]]s, and [[root canal]] filling. Barium sulfate is an ingredient in the [[rubber bullet|"rubber" pellets]] used by [[Carabineros de Chile|Chilean police]].<ref name=UChile>{{Cite news|title=Investigación U. de Chile comprueba que perdigones usados por Carabineros contienen solo 20 por ciento de goma|url=https://www.uchile.cl/noticias/159315/perdigones-usados-por-carabineros-contienen-solo-20-por-ciento-de-goma|date=November 18, 2019|access-date=June 29, 2020|work=Universidad de Chile}}</ref> This together with silica helps the pellet attain a 96.5 [[Shore durometer|shore A]] hardness.<ref name=UChile/> ====Catalyst support==== Barium sulfate is used as a [[catalyst support]] when selectively [[Hydrogenation|hydrogenating]] functional groups that are sensitive to [[Redox|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]]. ====Pyrotechnics==== 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. ====Copper industry==== As barium sulfate has a high [[melting point]] and is [[solubility|insoluble]] in water, it is used as a release material in casting of [[Copper_extraction#Electrorefining|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. ==== Radiometric measurements ==== Barium sulfate is sometimes used (or else PTFE) to coat the interior of integrating spheres due to the high reflectance of the material and near [[Lambertian reflectance|Lambertian characteristics]]. ==Production== 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 (fuel)|coke]]) to give [[barium sulfide]]: : BaSO₄ + 4 C → BaS + 4 CO 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: : BaS + H₂SO₄ → BaSO₄ + H₂S Barium sulfate produced in this way is often called {{lang|fr|blanc fixe}}, which is French for "permanent white". Blanc fixe is the form of barium encountered in consumer products, such as paints.<ref name=Ullmann/> 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 mineral deposit|hydrothermal conditions]] may contain many impurities, a.o., [[quartz]], or even amorphous [[silica]].<ref name="Fedele_2003">{{cite journal|last1=Fedele|first1=L.|last2=Todesca|first2=R.|last3=Boni|first3=M.|title=Barite-silica mineralization at the inter-Ordovician unconformity in southwestern Sardinia (Italy): a fluid inclusion study|journal=Mineralogy and Petrology|volume=77|issue=3–4|year=2003|pages=197–213|issn=0930-0708|doi=10.1007/s00710-002-0200-9|bibcode=2003MinPe..77..197F|s2cid=129874363}}</ref> ==History== 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]].<ref name=Holleman/> 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 [[Lead(II) sulfate|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 “[[Radioactive quackery|therapeutic hot-spring baths]]” in the area.<ref>{{cite journal |first1=Tieh-Chi |last1=Chu |first2=Jeng-Jong |last2=Wang |title=Radioactive Disequilibrium of Uranium and Thorium Nuclide Series in Hot Spring and River Water from Peitou Hot Spring Basin in Taipei |journal=Journal of Nuclear and Radiochemical Sciences |volume=1 |issue=1 |pages=5–10 |year=2000 |url=https://www.jstage.jst.go.jp/article/jnrs2000/1/1/1_1_5/_pdf |doi=10.14494/jnrs2000.1.5}}</ref> ==Safety aspects== 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&nbsp;mg/m³, while the [[National Institute for Occupational Safety and Health]] has a [[recommended exposure limit]] at 10&nbsp;mg/m³. For respiratory exposures, both agencies have set an occupational exposure limit at 5&nbsp;mg/m³.<ref>{{cite web | title = Barium Sulfate | work = NIOSH Pocket Guide to Chemical Hazards | publisher = Centers for Disease Control and Prevention | date = April 4, 2011 | url = https://www.cdc.gov/niosh/npg/npgd0047.html | access-date = November 18, 2013}}</ref> ==See also== * [[List of inorganic pigments]] * [[Baryte]] ==References== <references/> {{Barium compounds}} {{Contrast media}} {{Sulfates}} {{Authority control}} {{DEFAULTSORT:Barium Sulfate}} [[Category:Barium compounds]] [[Category:Sulfates]] [[Category:Inorganic pigments]] [[Category:Radiocontrast agents]]'