Potassium tetraiodomercurate(II)

Names
IUPAC name

potassium tetraiodidomercurate(II)

Other names

potassium mercuric iodide,
Nessler's reagent (principal component)

Identifiers

CAS Number

* 7783-33-7 Y

3D model (JSmol)

* Interactive image

ChEBI |

* CHEBI:51568 N

ChemSpider |

* 22948 N

EC Number |

* 231-990-4

PubChem CID

* 15980736

UNII |

* 7N83S6IU0F Y

UN number | 3287

InChI

* InChI=1S/Hg.4HI.2K/h;4*1H;;/q+2;;;;;2*+1/p-4 N

Key: OPCMAZHMYZRPID-UHFFFAOYSA-J N

SMILES

* [K+].[K+].I[Hg-2](I)(I)I

Properties

Chemical formula

| K
2[HgI
4][1]
Molar mass | 786.406 g·mol−1
Appearance  | yellow crystals
Odor | odorless
Density | 4.29 g/cm3

Solubility in water

| very soluble
Solubility | soluble in alcohol, ether, acetone
Hazards
Safety data sheet | External MSDS for Nessler's reagent
Related compounds

Other anions

| Mercury(II) iodide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Potassium tetraiodomercurate(II) is an inorganic compound with the chemical formula K
2[[[Chemistry:Mercury (element)|Hg]]I
4]. It consists of potassium cations and tetraiodomercurate(II) anions. It is the active agent in Nessler's reagent, used for detection of ammonia.[2]

## Contents

* 1 Preparation
* 2 Applications
* 2.1 Nessler's reagent
* 3 References
* 4 External links

## 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 K[Hg(H
2O)I
3] instead.[3]

## Applications

2[HgI
4] is a precursor to analogous copper and silver salts M
2[HgI
4] (M=Cu, Ag).[4]

### 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 (NH
3). At higher concentrations, a brown precipitate derivative of Millon's base (HgO * Hg(NH
2)Cl) may form. The sensitivity as a spot test is about 0.3 μg NH
3 in 2 μL.[5]

NH+
4 \+ 2 [HgI
4]2− \+ 4 OH−
→ HgO * Hg(NH
2)I↓ + 7 I−
\+ 3 H

The brown precipitate is not fully characterized and may vary from HgO * Hg(NH
2)I to 3HgO * Hg(NH

2.[6]

## References

1. ↑ Lide, David R., ed (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. p. 4-82. ISBN 978-1-4200-9084-0.
2. ↑ Template:VogelQualitative
3. ↑ Wagenknecht, F.; Juza, R. (1963). "Potassium Triiodomercurate(II)". in Brauer, G.. Handbook of Preparative Inorganic Chemistry. 1 (2nd ed.). Academic Press. p. 1100. https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/.
4. ↑ Wagenknecht, F.; Juza, R. (1963). "Copper(I) Tetraiodomercurate(II)". in Brauer, G.. Handbook of Preparative Inorganic Chemistry. 1 (2nd ed.). Academic Press. p. 1100. https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1155/.
5. ↑ Template:VogelQualitative4th
6. ↑ Template:VogelQualitative5th

## External links

* IARC Monograph: "Mercury and Mercury Compounds"
* National Pollutant Inventory - Mercury and compounds fact sheet

* v
* t
* e

Mercury compounds

Mercury(I)|

* HgH
* Hg2H2
* Hg2Br2
* Hg2Cl2
* Hg2F2
* Hg2I2
* Hg2(NO3)2
* Hg2O
* Hg2CO3
* Hg2SO4

Mercury(II)|

* HgH2
* HgNH2Cl
* HgSe
* HgS
* HgTe
* Hg(O2CCH3)2
* HgBr2
* HgCl2
* Hg(CN)2
* HgF2
* Hg(OH)2
* HgI2
* Hg(NO3)2
* HgO
* HgSO4
* Hg(SCN)2
* Hg(CNO)2
* Hg3N2
* Hg(Si(CH3)3)2
* K2HgI4

| Organomercury
compounds|

* Hg(CH3)2
* Hg(C2H5)2
* Hg(C6H5)2
* HgC6H5CH3CO2
* HgC6H5OB(OH)2
* HgC6H5NO3
* HgC6H5CCl3
* HgClC6H4CO2H
* HgOHCH2CHOCH3CH2(NHCO)2C2H4CO2H
* HgOHCH2CHOCH3CH2NHCOC6H4OCH2CO2H
* Na2HgOHC6HOBrC6H2OBrOCHC6H4CO2
* HgOC6H2CH3NO2
* NaHgC2H5SC6H4CO2

|

Mercury(IV)|

* HgF4 (hypothetical)

Amalgams|

* Na(Hg)
* Al(Hg)
* K(Hg)
* Au(Hg)
* Tl(Hg)
* Sn(Hg)

Mercury cations|

* Hg2+
* Hg22+
* Hg32+
* Hg42+
* Hg34+
* HgCH3+
* HgC2H5+
* HgC6H5+

* v
* t
* e

Potassium compounds

* KAsO2
* KBr
* KBrO3
* KCN
* KCNO
* KCl
* KClO
* KClO3
* KClO4
* KF
* KH
* KHCO2
* KHCO3
* KHF2
* KHS
* KHSO3
* KHSO4
* KH2AsO4
* KH2PO3
* KH2PO4
* KI
* KIO3
* KIO4
* KMnO4
* KNH2
* KN3
* K3N
* KNO2
* KNO3
* KOCN
* KOH
* KO2
* KPF6
* KSCN
* KCH3COO
* K2Al2O4
* K2CO3
* K2CrO4
* K2Cr2O7
* K2FeO4
* K2HPO4
* K2MnO4
* K2O
* K2O2
* K2PtCl4
* K2PtCl6
* K2S
* K2SeO4
* K2SO3
* K2SO4
* KHSO5
* K2S2O5
* K2S2O7
* K2S2O8
* K2Po
* K2SiO3
* K3[Fe(CN)6]
* K3[Fe(C2O4)3]
* K4[Fe(CN)6]
* K3PO4
* K4Mo2Cl8

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