potassium tetraiodomercurate(II)
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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)
| OtherNames = potassium mercuric iodide,
Nessler's reagent (principal component)
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| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 7783-33-7
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 7N83S6IU0F
| EINECS = 231-990-4
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| UNNumber = 3287
| PubChem = 15980736
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 22948
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 51568
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/Hg.4HI.2K/h;4*1H;;/q+2;;;;;2*+1/p-4
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = OPCMAZHMYZRPID-UHFFFAOYSA-J
| SMILES = [K+].[K+].I[Hg-2](I)(I)I
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| Section2 = {{Chembox Properties
| Formula = {{chem2|K2[HgI4]}}{{CRC90|page=4-82}}
| K=2|Hg=1|I=4
| Appearance = yellow crystals
| Odor = odorless
| Density = 4.29 g/cm3
| Solubility = very soluble
| SolubleOther = soluble in alcohol, ether, acetone
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| pKa =
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| Section7 = {{Chembox Hazards
| ExternalSDS = [http://msds.chem.ox.ac.uk/NE/Nesslers_reagent.html External MSDS for Nessler's reagent]
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| Section8 = {{Chembox Related
| 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.{{VogelQualitative}}
Preparation
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 monohydrate {{chem2|K[Hg(H2O)I3]}} instead.{{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}}
Applications
{{chem2|K2[HgI4]}} is a precursor to analogous copper and silver salts {{chem2|M2[HgI4]}} (M=Cu, Ag).{{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}}
=Nessler's reagent=
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 in 2 μL.{{VogelQualitative4th|page=319}}
:{{chem2|NH4+ + 2 [HgI4](2−) + 4 OH− → HgO*Hg(NH2)I↓ + 7 I− + 3 H2O}}
The brown precipitate is not fully characterized and may vary from {{chem2|HgO*Hg(NH2)I}} to {{chem2|3HgO*Hg(NH3)2I2}}.{{VogelQualitative5th|pages=293–294}}
References
External links
- [https://web.archive.org/web/20051015082344/http://www-cie.iarc.fr/htdocs/monographs/vol58/mono58-3.htm IARC Monograph: "Mercury and Mercury Compounds"]
- [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]
{{Mercury compounds}}
{{potassium compounds}}
Category:Mercury(II) compounds
Category:IARC Group 3 carcinogens