# Murexide

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> Source: https://en.wikipedia.org/wiki/Murexide
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{{chembox
| Verifiedfields = changed
| verifiedrevid = 447621203
|ImageFile1=Murexide.png{{!}}class=skin-invert
|ImageSize1=230px
|ImageFile2=Murexid powder.jpg
|ImageSize2=80px
|IUPACName=Ammonium 2,6-dioxo-5-[(2,4,6-trioxo-5-hexahydropyrimidinylidene)amino]-3''H''-pyrimidin-4-olate
|OtherNames=Purpuric acid ammonium salt
|Section1= {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo=3051-09-0
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 6032-80-0
| CASNo2_Comment = (hydrate)
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 17264
| EC_number = 221-266-6
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4W6L62S876
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = 221FEY2154
| UNII2_Comment = (hydrate)
| PubChem=18275
| SMILES = [O-]\C2=C(/N=C1\C(=O)NC(=O)NC1=O)C(=O)NC(=O)N2.[NH4+]
| InChI = 1/C8H5N5O6.H3N/c14-3-1(4(15)11-7(18)10-3)9-2-5(16)12-8(19)13-6(2)17;/h(H2,10,11,14,15,18)(H3,12,13,16,17,19);1H3
| InChIKey = LJYRLGOJYKPILZ-UHFFFAOYAL
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C8H5N5O6.H3N/c14-3-1(4(15)11-7(18)10-3)9-2-5(16)12-8(19)13-6(2)17;/h(H2,10,11,14,15,18)(H3,12,13,16,17,19);1H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = LJYRLGOJYKPILZ-UHFFFAOYSA-N
}}
|Section2= {{Chembox Properties
| C = 8
| H = 8
| N = 6
| O = 6
| Appearance=
| Density=1.72 g/cm<sup>3</sup> (hydrate&nbsp;of ammonium salt)
| MeltingPt=
| BoilingPt=
| Solubility=
  }}
|Section3= {{Chembox Hazards
| MainHazards=
| FlashPt=
| AutoignitionPt=
  }}
}}

'''Murexide''' (NH<sub>4</sub>C<sub>8</sub>H<sub>4</sub>N<sub>5</sub>O<sub>6</sub>, or C<sub>8</sub>H<sub>5</sub>N<sub>5</sub>O<sub>6</sub>·NH<sub>3</sub>), also called '''ammonium purpurate''' or '''MX''', is the [ammonium](/source/ammonium) [salt](/source/salt_(chemistry)) of [purpuric acid](/source/purpuric_acid). It is a purple solid that is soluble in water.  The compound was once used as an [indicator reagent](/source/complexometric_indicator).<ref name=Ray/> Aqueous solutions are yellow at low [pH](/source/pH), reddish-purple in weakly acidic solutions, and blue-purple in alkaline solutions.

==Preparation==
Murexide is prepared by treating [alloxantin](/source/alloxantin) with [ammonia](/source/ammonia) to 100&nbsp;°C, or by treating uramil (5-aminobarbituric acid) with [mercury oxide](/source/mercury_oxide).<ref>Some information on the chemist [W.&nbsp;N. Hartley](/source/Walter_Noel_Hartley) is available [http://w3.icr.com.au/~mcameron/WN%20Hartley%20&%20family.html here] {{webarchive|url=https://web.archive.org/web/20130526145921/http://w3.icr.com.au/~mcameron/WN%20Hartley%20%26%20family.html |date=2013-05-26 }}.</ref> It may also be prepared by digesting [alloxan](/source/alloxan) with [alcoholic](/source/alcoholic) ammonia.

==History==
[Justus von Liebig](/source/Justus_von_Liebig) and [Friedrich Wöhler](/source/Friedrich_W%C3%B6hler) in Giessen, Germany, had investigated the purple product, murexide, obtained from snake excrement in the 1830s, but this was not an abundant raw material, and a method of using it as a dyestuff was not established at that time.<ref>{{citation |title= A History of the International Dyestuff Industry | author= Peter J. T. Morris |author2=Anthony S. Travis |journal=American Dyestuff Reporter |volume= 81 |number= 11 |date= November 1992 |url=http://colorantshistory.org/HistoryInternationalDyeIndustryRev1/HistoryInternationalDyestuffIndustryFirefox/dyestuffs.html
|archive-url=https://web.archive.org/web/20070611123316/http://colorantshistory.org/HistoryInternationalDyeIndustryRev1/HistoryInternationalDyestuffIndustryFirefox/dyestuffs.html
|url-status=usurped
|archive-date=June 11, 2007
}}</ref> In the 1850s, French colourists and dye-producers, such as Depoully in Paris, succeeded in making murexide from abundant South American guano and of applying it to natural fibres. It was then widely adopted in Britain, France and Germany.

==Use==

Murexide is used in [analytical chemistry](/source/analytical_chemistry) as a [complexometric indicator](/source/complexometric_indicator) for complexometric titrations, most often of [calcium](/source/calcium) ions,<ref>{{cite journal |doi=10.1111/j.1471-0307.2010.00639.x|title=The Measurement and Significance of Ionic Calcium in Milk - A review|year=2011|last1=Lewis|first1=Michael J.|journal=International Journal of Dairy Technology|volume=64|pages=1–13|doi-access=free}}</ref> but also for [copper](/source/copper), [nickel](/source/nickel), [cobalt](/source/cobalt), [thorium](/source/thorium) and [rare-earth](/source/rare-earth) metals. It functions as a tridentate ligand.<ref name=Ray>{{cite journal |doi=10.1039/DT9770001336|title=Structural Studies in Metal–Purpurate Complexes. Part 1. Crystal Ctructures of Potassium Purpurate Trihydrate and Ammonium Purpurate Monohydrate (Murexide)|year=1977|last1=Martin|first1=Raymond L.|last2=White|first2=Allan H.|last3=Willis|first3=Anthony C.|journal=J. Chem. Soc., Dalton Trans.|issue=14|pages=1336–1342}}</ref>

Its use has been eclipsed by calcium-[ion selective electrode](/source/ion_selective_electrode)s.

==References==
{{Reflist}}
{{EB1911|wstitle=Murexide|volume=19|page=36}}

{{Ammonium salts}}

Category:Ammonium compounds
Category:Complexometric indicators
Category:Dyes
Category:Pyrimidines
Category:Lactams
Category:Enones

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Adapted from the Wikipedia article [Murexide](https://en.wikipedia.org/wiki/Murexide) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Murexide?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.