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{{short description|Inorganic compound}}
{{Short description|Inorganic chemical compound}}
{{redirect|BaSO4|the mineral|Baryte}}
{{chembox
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
|Verifiedfields = changed
|Watchedfields = changed
| verifiedrevid = 476997146
|verifiedrevid = 476997146
| ImageFile = Barium-sulfate-2D.png
|ImageFile = Bariumsulfatpulver.png
| ImageSize = 225px
|ImageFile1 = Barium-sulfate-2D.png
| ImageName = Chemical structure of barium sulfate
|ImageSize1 = 225px
| ImageFileL2 = Barite-unit-cell-3D-vdW.png
| ImageNameL2 = 3D model of barium sulfate
|ImageName1 = Chemical structure of barium sulfate
|ImageFileL2 = Barite-unit-cell-3D-vdW.png
| ImageFileR2 = Bariumsulfatpulver.png
|ImageNameL2 = 3D model of barium sulfate
| IUPACName =
| OtherNames =
|Section1={{Chembox Identifiers
|Section1={{Chembox Identifiers
|UNII_Ref = {{fdacite|correct|FDA}}
| Abbreviations =
|UNII = 25BB7EKE2E
| UNII_Ref = {{fdacite|correct|FDA}}
|ChEMBL_Ref = {{ebicite|changed|EBI}}
| UNII = 25BB7EKE2E
|ChEMBL = 2105897
| ChEMBL_Ref = {{ebicite|changed|EBI}}
|InChIKey = TZCXTZWJZNENPQ-NUQVWONBAD
| ChEMBL = 2105897
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = TZCXTZWJZNENPQ-NUQVWONBAD
|StdInChI = 1S/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey_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 = TZCXTZWJZNENPQ-UHFFFAOYSA-L
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|CASNo = 7727-43-7
| StdInChIKey = TZCXTZWJZNENPQ-UHFFFAOYSA-L
|CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 7727-43-7
| CASNo_Ref = {{cascite|correct|CAS}}
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID =22823
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|EINECS = 231-784-4
| ChemSpiderID =22823
|PubChem = 24414
| EINECS = 231-784-4
|SMILES = [Ba+2].[O-]S([O-])(=O)=O
| PubChem = 24414
|InChI = 1/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
| SMILES = [Ba+2].[O-]S([O-])(=O)=O
|RTECS = CR060000
| InChI = 1/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
|ChEBI_Ref = {{ebicite|changed|EBI}}
| RTECS = CR060000
|ChEBI = 133326
| MeSHName =
| ChEBI_Ref = {{ebicite|changed|EBI}}
|KEGG_Ref = {{keggcite|correct|kegg}}
| ChEBI = 133326
|KEGG = D02052
|DrugBank = DB11150
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D02052
|UNNumber = 1564
| DrugBank = DB11150
| UNNumber = 1564
}}
}}
|Section2={{Chembox Properties
|Section2={{Chembox Properties
| Formula = BaSO<sub>4</sub>
|Formula = BaSO<sub>4</sub>
| MolarMass = 233.38 g/mol
|MolarMass = 233.39 g/mol
| Appearance = white crystalline
|Appearance = white crystalline
| Odor = odorless
|Odor = odorless
| Density = 4.49 g/cm<sup>3</sup>
|Density = 4.49 g/cm<sup>3</sup>
| MeltingPtC = 1580
|MeltingPtC = 1580
|BoilingPtC = 1600
| MeltingPt_notes =
|BoilingPt_notes = (decomposes)
| BoilingPtC = 1600
|Solubility = 0.2448&nbsp;mg/100&nbsp;mL (20&nbsp;°C) <br> 0.285&nbsp;mg/100&nbsp;mL (30&nbsp;°C)
| 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<sup>−10</sup> (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=https://archive.org/details/crchandbookofche81lide/page/4 |url-access=registration}}</ref> soluble in concentrated, hot [[sulfuric acid]]
| SolubilityProduct = 1.0842 × 10<sup>−10</sup> (25&nbsp;°C)
|RefractIndex = 1.636 (alpha)
| SolubleOther = insoluble in [[ethanol|alcohol]],<ref>{{cite book
|MagSus = −71.3·10<sup>−6</sup> cm<sup>3</sup>/mol
| 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<sup>−6</sup> cm<sup>3</sup>/mol
}}
|Section3={{Chembox Structure
|Section3={{Chembox Structure
| CrystalStruct = orthorhombic
|CrystalStruct = orthorhombic
}}
}}
|Section5={{Chembox Thermochemistry
|Section4={{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>
|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"/>
|Entropy = 132&nbsp;J/(mol·K)<ref name="Zumdahl, Steven S. 2009"/>
|HeatCapacity = 101.7 J/(mol K)
}}
}}
|Section6={{Chembox Pharmacology
|Section5={{Chembox Pharmacology
| ATCCode_prefix = V08
|ATCCode_prefix = V08
| ATCCode_suffix = BA01
|ATCCode_suffix = BA01
| AdminRoutes = by mouth, rectal
|AdminRoutes = by mouth, rectal
| Bioavail = negligible by mouth
|Bioavail = negligible by mouth
|Excretion = rectal
| Metabolism =
|Legal_US = Rx only
| 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 =
| FlashPt = noncombustible
| FlashPt_notes=<ref name=PGCH/>
| AutoignitionPt =
| ExploLimits =
| PEL = TWA 15 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (resp)<ref name=PGCH>{{PGCH|0047}}</ref>
| REL = TWA 10 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (resp)<ref name=PGCH/>
| IDLH = N.D.<ref name=PGCH/>
}}
}}
|Section6={{Chembox Hazards
|PPhrases = {{P-phrases|260|264|270|273|314|501}}
|NFPA-H = 0
|NFPA-F = 0
|NFPA-R = 0
|FlashPt = noncombustible
|FlashPt_ref=<ref name=PGCH/>
|PEL = TWA 15 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (resp)<ref name=PGCH>{{PGCH|0047}}</ref>
|REL = TWA 10 mg/m<sup>3</sup> (total) TWA 5 mg/m<sup>3</sup> (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|SO<sub>4</sub>]]. 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>
'''Barium sulfate''' (or '''sulphate''') is the [[inorganic compound]] with the chemical formula [[barium|Ba]][[sulfate|SO<sub>4</sub>]]. It is a white crystalline solid that is odorless and [[solubility|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.<ref name=Holleman>Holleman, A. F. and Wiberg, E. (2001) ''Inorganic Chemistry'', San Diego, CA. Academic Press, {{ISBN|0-12-352651-5}}.</ref>


==Uses==
==Uses==

===Drilling fluids===
===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]].
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">{{cite book |chapter=Barium and Barium Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2007 |last1=Kresse |first1=Robert |last2=Baudis |first2=Ulrich |last3=Jäger |first3=Paul |last4=Riechers |first4=H. Hermann |last5=Wagner |first5=Heinz |last6=Winkler |first6=Jochen |last7=Wolf |first7=Hans Uwe |isbn=978-3-527-30673-2 |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===
===Radiocontrast agent===
{{Main|Barium sulfate suspension}}
{{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.
[[Barium sulfate suspension|Barium sulfate in suspension]] is often 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===
===Pigment===
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It is also used as a coating to diffuse light evenly.
It is also used as a coating to diffuse light evenly.


===Heat-reflecting paint===
===Light-reflecting paint for cooling===
Barium sulfate is highly reflective, of both visible and ultraviolet light.<ref name=":0">{{cite web |last=Puiu |first=Tibi |date=2022-10-04 |title=World's whitest paint is now thin enough to coat and cool down cars, trains and planes |website=ZME Science |language=en-US |url=https://www.zmescience.com/science/news-science/worlds-whitest-paint-usable-04102022/ |access-date=2022-10-12}}</ref> 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.<ref name="PurduePaint">{{cite web |last=Wiles |first=Kayla |date=September 16, 2021 |title=Purdue record for the whitest paint appears in latest edition of 'Guinness World Records' |website=purdue.edu |language=en |url=https://www.purdue.edu/newsroom/releases/2021/Q3/purdue-record-for-the-whitest-paint-appears-in-latest-edition-of-guinness-world-records.html |access-date=2022-10-12}}</ref> By using hexagonal nanoplatelet [[boron nitride]], the thickness of a coat of this type of paint was reduced to 0.15&nbsp;mm.<ref name=":0"/>
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.<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===
===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>
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. Baryta has also 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 November 2012</ref>


===Plastics filler===
===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}}
Barium sulfate is commonly used as a [[filler (materials)|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.<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 |pmc=7037949 |doi=10.3390/ijms21030833 |doi-access=free |pmid=32012889}}</ref> 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.<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 |date=2020-01-28 |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 |volume=21 |issue=3 |pages=833 |issn=1422-0067 |pmc=7037949 |doi=10.3390/ijms21030833 |doi-access=free |pmid=32012889}}</ref>

Barium sulfate can also be used to enhance the material properties of [[HDPE]],<ref>{{cite journal | last1=Chen|first1=X. |last2=Wang|first2= L.| last3 = Shi|first3 = J. | last4=Shi | first4=H. | last5=Liu | first5=Y.| title = Effect of Barium Sulfate Nanoparticles on Mechanical Properties and Crystallization Behaviour of HDPE | date = 2010 | journal = Polymers & Polymer Composites | volume = 18|issue=3 |page = 145-152|doi=10.1177/096739111001800304 }}</ref> although typically in relatively low concentrations, and often in combination with other fillers like [[calcium carbonate]] or [[titanium oxide]].


===Niche uses===
===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.
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 [[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.
In metal casting, the moulds used are often coated with barium sulfate in order to prevent the molten metal from bonding with the mould.
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It is also used in [[brake lining]]s, [[anechoic|anacoustic]] foams, [[powder coating]]s, and [[root canal]] filling.
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/>
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 |date=November 18, 2019 |work=Universidad de Chile |url=https://www.uchile.cl/noticias/159315/perdigones-usados-por-carabineros-contienen-solo-20-por-ciento-de-goma |access-date=June 29, 2020}}</ref> This together with silica helps the pellet attain a 96.5 [[Shore durometer|Shore A]] hardness.<ref name=UChile/>


====Catalyst support====
====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]].
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====
====Pyrotechnics====
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====Copper industry====
====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.
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#Refining|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 ====
====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]].
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 reflectance|Lambertian characteristics]].

====3D printing of firearms====
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.<ref name=BATF>{{cite news |title=Is a firearm illegal if it is made out of plastic? |date=September 23, 2016 |url=https://www.atf.gov/firearms/qa/firearm-illegal-if-it-made-plastic |access-date=March 4, 2023}}</ref>


==Production==
==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]]:
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]]:
: BaSO<sub>4</sub> + 4 C → BaS + 4 CO
: BaSO<sub>4</sub> + 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:
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 + H<sub>2</sub>SO<sub>4</sub> → BaSO<sub>4</sub> + H<sub>2</sub>S
: BaS + H<sub>2</sub>SO<sub>4</sub> → BaSO<sub>4</sub> + H<sub>2</sub>S

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/>
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 Ba<sup>2+</sup> ions, as well as for sulfate.
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 Ba<sup>2+</sup> 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>
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 |date=1 February 2003 |volume=77 |issue=3–4 |pages=197–213 |bibcode=2003MinPe..77..197F |doi=10.1007/s00710-002-0200-9 |s2cid=129874363}}</ref>


==History==
==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.
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|PbSO<sub>4</sub>]] and BaSO<sub>4</sub>, 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>
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|PbSO<sub>4</sub>]] and BaSO<sub>4</sub>, 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 |last1=Chu |first1=Tieh-Chi |last2=Wang |first2=Jeng-long |title=Radioactive Disequilihrium 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 |date=2000 |volume=1 |issue=1 |pages=5–10 |doi=10.14494/jnrs2000.1.5 |doi-access=free}}</ref>


==Safety aspects==
==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 BaSO<sub>4</sub>. 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/m<sup>3</sup>, while the [[National Institute for Occupational Safety and Health]] has a [[recommended exposure limit]] at 10&nbsp;mg/m<sup>3</sup>. For respiratory exposures, both agencies have set an occupational exposure limit at 5&nbsp;mg/m<sup>3</sup>.<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>
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 BaSO<sub>4</sub>. 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/m<sup>3</sup>, while the [[National Institute for Occupational Safety and Health]] has a [[recommended exposure limit]] at 10&nbsp;mg/m<sup>3</sup>. For respiratory exposures, both agencies have set an occupational exposure limit at 5&nbsp;mg/m<sup>3</sup>.<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==
==See also==
* [[List of inorganic pigments]]
* [[Baryte]]
* [[Baryte]]
* [[List of inorganic pigments]]


==References==
==References==
{{Reflist}}
<references/>


{{Barium compounds}}
{{Barium compounds}}
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{{Authority control}}
{{Authority control}}

{{DEFAULTSORT:Barium Sulfate}}
[[Category:Barium compounds]]
[[Category:Barium compounds]]
[[Category:Sulfates]]
[[Category:Sulfates]]

Latest revision as of 13:59, 8 November 2024

"BaSO4" redirects here. For the mineral, see Baryte.
Barium sulfate
Chemical structure of barium sulfate
3D model of barium sulfate
3D model of barium sulfate
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.028.896 Edit this at Wikidata
EC Number
  • 231-784-4
KEGG
RTECS number
  • CR060000
UNII
UN number 1564
  • InChI=1S/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 checkY
    Key: TZCXTZWJZNENPQ-UHFFFAOYSA-L checkY
  • InChI=1/Ba.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
    Key: TZCXTZWJZNENPQ-NUQVWONBAD
  • [Ba+2].[O-]S([O-])(=O)=O
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)
1.0842 × 10−10 (25 °C)
Solubility insoluble in alcohol,[1] soluble in concentrated, hot sulfuric acid
−71.3·10−6 cm3/mol
1.636 (alpha)
Structure
orthorhombic
Thermochemistry
101.7 J/(mol K)
132 J/(mol·K)[2]
−1465 kJ/mol[2]
Pharmacology
V08BA01 (WHO)
by mouth, rectal
Pharmacokinetics:
negligible by mouth
rectal
Legal status
Hazards
GHS labelling:
P260, P264, P270, P273, P314, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0
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).
☒N verify (what is checkY☒N ?)

Barium sulfate (or sulphate) is the inorganic compound with the chemical formula BaSO4. 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]

Uses

[edit]

Drilling fluids

[edit]

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.

Radiocontrast agent

[edit]
Main article: Barium sulfate suspension

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.

Pigment

[edit]

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.

Light-reflecting paint for cooling

[edit]

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]

Paper brightener

[edit]

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]

Plastics filler

[edit]

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 can also be used to enhance the material properties of HDPE,[13] although typically in relatively low concentrations, and often in combination with other fillers like calcium carbonate or titanium oxide.

Niche uses

[edit]

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.[14] This together with silica helps the pellet attain a 96.5 Shore A hardness.[14]

Catalyst support

[edit]

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.

Pyrotechnics

[edit]

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

[edit]

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.

Radiometric measurements

[edit]

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.

3D printing of firearms

[edit]

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.[15]

Production

[edit]

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:

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 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.[16]

History

[edit]

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.[17]

Safety aspects

[edit]

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.[18]

See also

[edit]

References

[edit]
  1. ^ CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. 2004. pp. 4–45. ISBN 0-8493-0485-7.
  2. ^ a b Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. ISBN 978-0-618-94690-7.
  3. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0047". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ a b Holleman, A. F. and Wiberg, E. (2001) Inorganic Chemistry, San Diego, CA. Academic Press, ISBN 0-12-352651-5.
  5. ^ a b c Kresse, Robert; Baudis, Ulrich; Jäger, Paul; Riechers, H. Hermann; Wagner, Heinz; Winkler, Jochen; Wolf, Hans Uwe (2007). "Barium and Barium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a03_325.pub2. ISBN 978-3-527-30673-2.
  6. ^ a b Puiu, Tibi (2022-10-04). "World's whitest paint is now thin enough to coat and cool down cars, trains and planes". ZME Science. Retrieved 2022-10-12.
  7. ^ Wiles, Kayla (September 16, 2021). "Purdue record for the whitest paint appears in latest edition of 'Guinness World Records'". purdue.edu. Retrieved 2022-10-12.
  8. ^ The Getty Conservation Institute, Silver Gelatin. The Atlas of Analytical Signatures of Photographic Processes. J. Paul Getty Trust, 2013.
  9. ^ Salvaggio, Nanette L. Basic Photographic Materials and Processes. Taylor & Francis US, Oct 27, 2008. p. 362.
  10. ^ 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 November 2012
  11. ^ Lopresti, Mattia; Alberto, Gabriele; Cantamessa, Simone; Cantino, Giorgio; Conterosito, Eleonora; Palin, Luca; Milanesio, Marco (28 January 2020). "Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study". International Journal of Molecular Sciences. 21 (3): 833. doi:10.3390/ijms21030833. PMC 7037949. PMID 32012889.
  12. ^ Lopresti, Mattia; Alberto, Gabriele; Cantamessa, Simone; Cantino, Giorgio; Conterosito, Eleonora; Palin, Luca; Milanesio, Marco (2020-01-28). "Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study". International Journal of Molecular Sciences. 21 (3): 833. doi:10.3390/ijms21030833. ISSN 1422-0067. PMC 7037949. PMID 32012889.
  13. ^ Chen, X.; Wang, L.; Shi, J.; Shi, H.; Liu, Y. (2010). "Effect of Barium Sulfate Nanoparticles on Mechanical Properties and Crystallization Behaviour of HDPE". Polymers & Polymer Composites. 18 (3): 145-152. doi:10.1177/096739111001800304.
  14. ^ a b "Investigación U. de Chile comprueba que perdigones usados por Carabineros contienen solo 20 por ciento de goma". Universidad de Chile. November 18, 2019. Retrieved June 29, 2020.
  15. ^ "Is a firearm illegal if it is made out of plastic?". September 23, 2016. Retrieved March 4, 2023.
  16. ^ Fedele, L.; Todesca, R.; Boni, M. (1 February 2003). "Barite-silica mineralization at the inter-Ordovician unconformity in southwestern Sardinia (Italy): a fluid inclusion study". Mineralogy and Petrology. 77 (3–4): 197–213. Bibcode:2003MinPe..77..197F. doi:10.1007/s00710-002-0200-9. S2CID 129874363.
  17. ^ Chu, Tieh-Chi; Wang, Jeng-long (2000). "Radioactive Disequilihrium of Uranium and Thorium Nuclide Series in Hot Spring and River Water from Peitou Hot Spring Basin in Taipei". Journal of Nuclear and Radiochemical Sciences. 1 (1): 5–10. doi:10.14494/jnrs2000.1.5.
  18. ^ "Barium Sulfate". NIOSH Pocket Guide to Chemical Hazards. Centers for Disease Control and Prevention. April 4, 2011. Retrieved November 18, 2013.
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