Potassium tetraiodomercurate(II): Difference between revisions
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| ImageFile = Potassium tetraiodomercurate(II).png |
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| ImageFile1 = Potassium tetraiodomercurate(II)-3D-vdW.png |
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| IUPACName = potassium tetraiodidomercurate(II) |
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| Section1 = {{Chembox Identifiers |
| Section1 = {{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 7783-33-7 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| EINECS = |
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| UNII = 7N83S6IU0F |
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| EINECS = 231-990-4 |
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| UNNumber = 3287 |
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| PubChem = 15980736 |
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| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} |
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| ChemSpiderID = 22948 |
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| ChEBI_Ref = {{ebicite|changed|EBI}} |
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| ChEBI = 51568 |
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| StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChI = 1S/Hg.4HI.2K/h;4*1H;;/q+2;;;;;2*+1/p-4 |
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| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChIKey = OPCMAZHMYZRPID-UHFFFAOYSA-J |
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| SMILES = [K+].[K+].I[Hg-2](I)(I)I |
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| Formula = {{chem2|K2[HgI4]}}<ref name=crc>{{CRC90|page=4-82}}</ref> |
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| K=2|Hg=1|I=4 |
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| Appearance = yellow crystals |
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| Odor = odorless |
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| SolubleOther = soluble in [[ethanol|alcohol]], [[diethyl ether|ether]], [[acetone]] |
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| pKa = |
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| ExternalSDS = [http://msds.chem.ox.ac.uk/NE/Nesslers_reagent.html External MSDS for Nessler's reagent] |
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| Section8 = {{Chembox Related |
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| OtherAnions = [[Mercury(II) iodide]] |
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'''Potassium tetraiodomercurate(II)''' is an [[inorganic compound]] with the [[chemical formula]] {{chem2|K2[HgI4]|auto=1}}. It consists of [[potassium]] cations and tetraiodomercurate(II) anions. It is the active agent in Nessler's reagent, used for detection of [[ammonia]].<ref>{{VogelQualitative}} |
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[[Image:TetraiodomercuratII.svg|thumb|left|The tetraiodomercurate(II) anion]] |
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</ref> |
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'''Potassium tetraiodomercurate(II)''' is an inorganic compound containing potassium cations and the tetraiodomercurate(II) complex anion. It is mainly used as '''Neßler's reagent''', a 0.09 mol/L solution of potassium tetraiodomercurate(II) (K<sub>2</sub>[HgI<sub>4</sub>]) in 2.5 mol/L potassium hydroxide, used to detect [[ammonia]]. |
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==Preparation== |
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<br clear = left/> |
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The compound crystallizes from a heated solution of [[mercuric iodide]], [[potassium iodide]], and precisely 2% [[water]] in [[acetone]]. Attempted synthesis in concentrated [[aqueous solution]] will give the pale orange [[water of crystallization|monohydrate]] {{chem2|K[Hg(H2O)I3]}} instead.<ref>{{cite book |last1=Wagenknecht |first1=F. |title=Handbook of Preparative Inorganic Chemistry |last2=Juza |first2=R. |publisher=Academic Press |year=1963 |editor-last=Brauer |editor-first=G. |edition=2nd |volume=1 |page=1100 |chapter=Potassium Triiodomercurate(II) |chapter-url=https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/ |via=the [[Internet Archive]]}}</ref> |
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Named after [[Julius Neßler]], when this solution gives a yellow coloration, it indicates the presence of ammonia: at higher concentrations, a brown [[precipitate]] may form. The sensitivity as a [[spot test]] is about 0.3 μg NH<sub>3</sub> in 2 μL.{{Citation needed|date=August 2010}} |
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== Applications == |
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:NH<sub>4</sub><sup>+</sup> + 2[HgI<sub>4</sub>]<sup>2</sup><sup>−</sup> + 4OH<sup>−</sup> → HgO·Hg(NH<sub>2</sub>)I + 7I<sup>−</sup> + 3H<sub>2</sub>O |
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{{chem2|K2[HgI4]}} is a precursor to analogous [[copper]] and [[silver]] salts {{chem2|M2[HgI4]}} (M=Cu, Ag).<ref>{{cite book |last1=Wagenknecht |first1=F. |url= |title=Handbook of Preparative Inorganic Chemistry |last2=Juza |first2=R. |publisher=Academic Press |year=1963 |editor-last=Brauer |editor-first=G. |edition=2nd |volume=1 |page=1100 |chapter=Copper(I) Tetraiodomercurate(II) |chapter-url=https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/ |via=the [[Internet Archive]]}}</ref> |
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Nessler's reagent is generally prepared from [[potassium iodide]] and [[mercury(II) chloride]]. A hot concentrated solution of [[mercury(II) chloride]] is added to concentrated solution of potassium iodide, until the precipitate of mercury(II) iodide stops dissolving. The liquid is filtered, and [[potassium hydroxide]] and a further bit of mercury(II) chloride solution are added. The resulting solution is then cooled and diluted to required concentration.<ref>http://www.fao.org/docrep/field/003/Q6501E/Q6501E05.htm</ref> Nessler's reagent may be used with [[Nessler tube]]s. |
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'''Nessler's reagent''', named after [[Julius Neßler]] (Nessler), is a 0.09 mol/L solution of potassium tetraiodomercurate(II) in 2.5 mol/L [[potassium hydroxide]]. This pale solution becomes deeper yellow in the presence of [[ammonia]] ({{chem2|NH3}}). At higher concentrations, a brown [[precipitate]] derivative of [[Millon's base]] ({{chem2|HgO*Hg(NH2)Cl}}) may form. The sensitivity as a [[spot test]] is about 0.3 μg [[Ammonia|{{chem2|NH3}}]] in 2 μL.<ref name="Vogel4th-319">{{VogelQualitative4th|page=319}}</ref> |
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:{{chem2|NH4+ + 2 [HgI4](2−) + 4 OH− → HgO*Hg(NH2)I↓ + 7 I− + 3 H2O}} |
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The brown precipitate is not fully characterized and may vary from {{chem2|HgO*Hg(NH2)I}} to {{chem2|3HgO*Hg(NH3)2I2}}.<ref>{{VogelQualitative5th|pages=293–294}}</ref> |
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==References== |
==References== |
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<references/> |
<references/> |
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*{{VogelQualitative}} |
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==Further reading== |
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* {{cite journal | last1 = Mok | first1 = K. F. | last2 = McKee | first2 = V. | title = Structure of a dipotassium tetraiodomercurate(II) salt with dibenzo-18-crown-6 | journal = Acta Crystallographica C | volume = 46 | pages = 2078 | year = 1990 | doi = 10.1107/S0108270190003742}} |
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==External links== |
==External links== |
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*[http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-3.htm IARC Monograph: "Mercury and Mercury Compounds"] |
*[https://web.archive.org/web/20051015082344/http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-3.htm IARC Monograph: "Mercury and Mercury Compounds"] |
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*[http://www.npi.gov.au/database/substance-info/profiles/53.html National Pollutant Inventory - Mercury and compounds fact sheet] |
*[https://web.archive.org/web/20060425193836/http://www.npi.gov.au/database/substance-info/profiles/53.html National Pollutant Inventory - Mercury and compounds fact sheet] |
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{{Mercury compounds}} |
{{Mercury compounds}} |
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{{potassium compounds}} |
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[[Category: |
[[Category:Iodo complexes]] |
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[[Category:Potassium compounds]] |
[[Category:Potassium compounds]] |
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[[Category:Mercury compounds]] |
[[Category:Mercury(II) compounds]] |
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[[Category:IARC Group 3 carcinogens]] |
[[Category:IARC Group 3 carcinogens]] |
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[[Category:Coordination |
[[Category:Coordination complexes]] |
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[[Category:Chemical tests]] |
[[Category:Chemical tests]] |
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[[de:Kaliumtetraiodomercurat(II)]] |
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[[ja:ネスラー試薬]] |
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[[sl:Nesslerjev reagent]] |
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[[zh:碘化汞钾]] |