Editing Barium hydroxide

{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 476994496
| Name = Barium hydroxide
| ImageFile1  = Ba(OH)2monohydrate.tif
| ImageFile2 = Ba(OH)2 octahydrate.JPG
| ImageName = Barium hydroxide octahydrate
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 26408
| InChI = 1/Ba.2H2O/h;2*1H2/q+2;;/p-2
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 32592
| SMILES = [Ba+2].[OH-].[OH-]
| InChIKey = RQPZNWPYLFFXCP-NUQVWONBAR
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Ba.2H2O/h;2*1H2/q+2;;/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = RQPZNWPYLFFXCP-UHFFFAOYSA-L
| CASNo = 17194-00-2
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 22326-55-2
| CASNo2_Comment = (monohydrate)
| CASNo3_Ref = {{cascite|correct|CAS}}
| CASNo3 = 12230-71-6
| CASNo3_Comment = (octahydrate)
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 1OHB71MYBK
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = P27GID97XM
| UNII2_Comment = (monohydrate)
| UNII3_Ref = {{fdacite|correct|FDA}}
| UNII3 = L5Q5V03TBN
| UNII3_Comment = (octahydrate)
| RTECS = CQ9200000
| PubChem = 28387
| Gmelin = 846955
| EINECS = 241-234-5
  }}
|Section2={{Chembox Properties
| Formula = Ba(OH)<sub>2</sub>
| MolarMass = 171.34 g/mol (anhydrous) <br> 189.355 g/mol (monohydrate) <br> 315.46 g/mol (octahydrate)
| Appearance = white solid
| Solubility = ''mass of BaO (not Ba(OH)<sub>2</sub>):'' <br> 1.67 g/100 mL (0&nbsp;°C) <br> 3.89 g/100 mL (20&nbsp;°C) <br> 4.68 g/100 mL (25&nbsp;°C) <br> 5.59 g/100 mL (30&nbsp;°C) <br> 8.22 g/100 mL (40&nbsp;°C) <br> 11.7 g/100 mL (50&nbsp;°C)  <br> 20.94 g/100 mL (60&nbsp;°C) <br> 101.4 g/100 mL (100&nbsp;°C){{Citation needed|date=May 2020}}
| Solvent = other solvents
| SolubleOther = low
| MeltingPtC = 78
| MeltingPt_notes = (octahydrate)<br/>300&nbsp;°C (monohydrate) <br> 407&nbsp;°C (anhydrous)
| BoilingPtC = 780
| BoilingPt_notes = 
| Density = 3.743 g/cm<sup>3</sup> (monohydrate) <br> 2.18 g/cm<sup>3</sup> (octahydrate, 16&nbsp;°C)
| RefractIndex = 1.50 (octahydrate) 
| pKb = 0.15 (first OH<sup>–</sup>), 0.64 (second OH<sup>–</sup>)<ref>{{cite web|language=de|url=http://www.periodensystem-online.de/index.php?show=list&id=acid&prop=pKb-Werte&sel=oz&el=92|title=Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. - Das Periodensystem online}}</ref>
| MagSus = −53.2·10<sup>−6</sup> cm<sup>3</sup>/mol  }}
|Section3={{Chembox Structure
| Coordination = 
| CrystalStruct = octahedral
  }}
|Section4={{Chembox Thermochemistry
| Thermochemistry_ref = <ref>{{CRC90}}</ref>
| DeltaHf = &minus;944.7&nbsp;kJ·mol<sup>−1</sup>
| DeltaHfus = 16&nbsp;kJ·mol<sup>−1</sup>
  }}
|Section7={{Chembox Hazards
| NFPA-H = 3
| NFPA-F = 1
| NFPA-R = 1
| GHSPictograms = {{GHS05}}{{GHS07}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|302|314|332|412}}
| PPhrases = {{P-phrases|}}
| FlashPt = Non-flammable
| LD50 = 308 mg/kg (rat, oral)
| ExternalSDS = [https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-b/S25188.pdf Fisher Scientific]
  }}
|Section8={{Chembox Related
| OtherAnions = [[Barium oxide]]<br />[[Barium peroxide]]
| OtherCations = [[Calcium hydroxide]]<br />[[Strontium hydroxide]]
  }}
}}

'''Barium hydroxide''' is a [[chemical compound]] with the [[chemical formula]] Ba(OH)<sub>2</sub>.  The monohydrate (''x'' = 1), known as baryta or baryta-water, is one of the principal compounds of [[barium]]. This white granular [[Hydrate|monohydrate]] is the usual commercial form.

==Preparation and structure==
Barium hydroxide can be prepared by dissolving [[barium oxide]] (BaO) in [[water]]:

:BaO + H<sub>2</sub>O → Ba(OH)<sub>2</sub>

It crystallises as the octahydrate, which converts to the monohydrate upon heating in air.  At  100&nbsp;°C in a vacuum, the monohydrate will yield BaO and water.<ref>(1960). ''Gmelins Handbuch der anorganischen Chemie (8. Aufl.)'', Weinheim: Verlag Chemie, p. 289.</ref>  The monohydrate adopts a layered structure (see picture above).  The Ba<sup>2+</sup> centers adopt a [[Square antiprismatic molecular geometry|square antiprismatic geometry]].  Each Ba<sup>2+</sup> center is bound by two water [[ligand]]s and six hydroxide ligands, which are respectively doubly and triply bridging to neighboring Ba<sup>2+</sup> centre sites.<ref>Kuske, P.; Engelen, B.; Henning, J.; Lutz, H.D.; Fuess, H.; Gregson, D. "Neutron diffraction study of Sr(OH)<sub>2</sub>(H<sub>2</sub>O) and beta-Ba(OH)<sub>2</sub>*(H<sub>2</sub>O)" Zeitschrift für Kristallographie (1979-2010) 1988, vol. 183, p319-p325.</ref>  In the octahydrate, the individual Ba<sup>2+</sup> centers are again eight coordinate but do not share ligands.<ref>Manohar, H.; Ramaseshan, S. "The crystal structure of barium hydroxide octahydrate Ba (OH)<sub>2</sub>(H<sub>2</sub>O)<sub>8</sub>" Zeitschrift für Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie 1964. vol. 119, p357-p374</ref>
[[File:Ba(OH)2O2HCoordSph.tif|thumb|left|Coordination sphere about an individual barium ion in Ba(OH)<sub>2</sub>.H<sub>2</sub>O.]]

==Uses==
Industrially, barium hydroxide is used as the precursor to other barium compounds.  The monohydrate is used to dehydrate and remove sulfate from various products.<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>  This application exploits the very low solubility of [[barium sulfate]].  This industrial application is also applied to laboratory uses.

===Laboratory uses===
Barium hydroxide is used in [[analytical chemistry]] for the [[titration]] of [[weak acid]]s, particularly [[organic acid]]s. Its aqueous solution, if clear, is guaranteed to be free of carbonate, unlike those of [[sodium hydroxide]] and [[potassium hydroxide]], as [[barium carbonate]] is insoluble in water. This allows the use of indicators such as [[phenolphthalein]] or [[thymolphthalein]] (with alkaline colour changes) without the risk of titration errors due to the presence of [[carbonate]] ions, which are much less basic.<ref>{{VogelQuantitative}}</ref>

Barium hydroxide is occasionally used in [[organic synthesis]] as a strong base, for example for the hydrolysis of esters<ref>Meyer, K.; Bloch, H. S. (1945). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0637 Naphthoresorcinol]". ''[[Org. Synth.]]'' '''25''': 73; ''Coll. Vol.'' '''3''': 637.</ref> and nitriles,<ref>Brown, G. B. (1946). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0615 Methylsuccinic acid]". ''[[Org. Synth.]]'' '''26''': 54; ''Coll. Vol.'' '''3''': 615.</ref><ref>Ford, Jared H. (1947). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0034 β-Alanine]". ''[[Org. Synth.]]'' '''27''': 1; ''Coll. Vol.'' '''3''': 34.</ref><ref>Anslow, W. K.; King, H.; Orten, J. M.; Hill, R. M. (1925). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0298 Glycine]". ''[[Org. Synth.]]'' '''4''': 31; ''Coll. Vol.'' '''1''': 298.</ref> and as a base in [[aldol condensation]]s.

:[[File:Barium hydroxide-catalyzed 2-carboxy-1,3-dihydroxynaphthalene preparation.svg|418px|class=skin-invert]]
:[[File:Barium hydroxide-catalyzed methylsuccinic acid preparation.svg|346px|class=skin-invert]]

There are several uses for barium hydroxide such as to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.<ref>Durham, L. J.; McLeod, D. J.; Cason, J. (1958). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0635 Methyl hydrogen hendecanedioate]". ''[[Org. Synth.]]'' '''38''':55; ''Coll. Vol.'' '''4''':635.</ref>

Barium hydroxide has also been used in the decarboxylation of amino acids liberating barium carbonate in the process.<ref>{{Cite book|url=https://books.google.com/books?id=S4nrnTkBph0C|title = Biochemistry and Clinical Pathology|isbn = 9788185790169|last1 = Chaudhari|first1 = M. R.|last2 = Kulkarni|first2 = Y. A.|last3 = Gokhale|first3 = S. B.|date = 6 October 2008| publisher=Pragati Books Pvt. }}</ref>

It is also used in the preparation of [[cyclopentanone]],<ref>Thorpe, J. F.; Kon, G. A. R. (1925). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0192 Cyclopentanone]". ''[[Org. Synth.]]'' '''5''': 37; ''Coll. Vol.'' '''1''': 192.</ref> [[diacetone alcohol]]<ref>Conant, J. B.; Tuttle, Niel. (1921). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0199 Diacetone alcohol]". ''[[Org. Synth.]]'' '''1''': 45; ''Coll. Vol.'' '''1''': 199.</ref> and [[Gulonic acid|<small>D</small>-gulonic γ-lactone]].<ref>Karabinos, J. V. (1956). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0506D-Gulonic γ-lactone]". ''[[Org. Synth.]]'' '''36''': 38; ''Coll. Vol.'' '''4''': 506.</ref>

:[[File:Cyclopentanone prepn.png|275px|class=skin-invert]]
:[[File:Barium hydroxide-catalyzed diacetone alcohol preparation.svg|275px|class=skin-invert]]

==Reactions==
Barium hydroxide decomposes to [[barium oxide]] when heated to 800&nbsp;°C.  Reaction with [[carbon dioxide]] gives [[barium carbonate]]. Its aqueous solution, being highly alkaline, undergoes neutralization reactions with acids. It is especially useful on reactions that require the titrations of weak organic acids. Thus, it forms [[barium sulfate]] and [[barium phosphate]] with sulfuric  and phosphoric acids, respectively.  Reaction with [[hydrogen sulfide]] produces [[barium sulfide]].  Precipitation of many insoluble, or less soluble barium salts, may result from double replacement reaction when a barium hydroxide aqueous solution is mixed with many solutions of other metal salts.<ref>Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, {{ISBN|0-07-049439-8}}</ref>

Reactions of barium hydroxide with [[ammonium]] salts are strongly [[endothermic]]. The reaction of barium hydroxide octahydrate with [[ammonium chloride]]<ref name=UCSD>{{cite web|title=Endothermic Reactions of Hydrated Barium Hydroxide and Ammonium Chloride|url=http://www-chem.ucsd.edu/undergraduate/teaching-labs/demos/demo45.html|publisher=UC San Diego|access-date=2 April 2014}}</ref><ref>[http://www.nuffieldfoundation.org/practical-chemistry/endothermic-solid-solid-reactions Endothermic Solid-Solid Reactions]</ref> or<ref name=UW /> [[ammonium thiocyanate]]<ref name=UW>{{cite web|last=Camp|first=Eric|title=Endothermic Reaction|url=http://depts.washington.edu/chem/facilserv/lecturedemo/EndothermicReaction-UWDept.ofChemistry.html|publisher=Univertist of Washington|access-date=2 April 2014}}</ref><ref name=RSC>{{cite web|title=Endothermic solid-solid reactions |url=http://media.rsc.org/Classic%20Chem%20Demos/CCD-44.pdf |work=Classic Chemistry Demonstrations |publisher=The Royal Society of Chemistry |access-date=2 April 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140407092124/http://media.rsc.org/Classic%20Chem%20Demos/CCD-44.pdf |archive-date=7 April 2014 }}</ref> is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.

==Safety==
Barium hydroxide presents the same hazards such as skin irritation and burns as well as eye damage, just as the other [[strong base]]s and as other water-soluble barium compounds: it is corrosive and toxic. {{Citation needed|date=November 2016}}

==See also==
* [[Baralyme]]

==References==
{{reflist}}

==External links==
*[http://hazard.com/msds/mf/baker/baker/files/b0422.htm Material Safety Data Sheet (MSDS)]

{{Barium compounds}}
{{Hydroxides}}

[[Category:Barium compounds]]
[[Category:Hydroxides]]