Chemistry:Mercury(II) iodide

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Mercury(II) iodide
Mercury(II)-iodide-xtal-3D-SF-A.png
Mercury(II) iodide (α form)
Mercury(II)-iodide-xtal-3D-SF-B.png
Mercury(II) iodide (β form)
Mercury iodide.jpg
β (left) and α (right) forms
Names
IUPAC name
Mercury(II) iodide
Other names
Mercury diiodide
Mercuric iodide
Red mercury (α form only)
Coccinite (α form only)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
DrugBank
EC Number
  • 231-873-8
277788
UNII
Properties
HgI2
Molar mass 454.40 g/mol
Appearance orange-red powder
Odor odorless
Density 6.36 g/cm3
Melting point 259 °C (498 °F; 532 K)
Boiling point 350 °C (662 °F; 623 K)
0.006 g/100 mL
2.9×10−29[1]
Solubility slightly soluble in alcohol, ether, acetone, chloroform, ethyl acetate, CS2, olive oil, castor oil

Soluble in excess KI(Potassium iodide) forming soluble complex K2[Hg2I4 ](Potassium tetraiodomercurate(II)) also known as Nessler's reagent

−128.6·10−6 cm3/mol
2.455
Structure
Tetrahedral
Pharmacology
1=ATC code }} D08AK30 (WHO)
Hazards
GHS pictograms GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
GHS Signal word Danger
H300, H310, H330, H373, H410
P260, P262, P264, P270, P271, P273, P280, P284, P301+310, P302+350, P304+340, P310, P314, P320, P321, P322, P330, P361, P363, P391, P403+233, P405, P501
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
3
0
Flash point Non-flammable
Related compounds
Other anions
Mercury(II) fluoride
Mercury(II) chloride
Mercury(II) bromide
Other cations
Zinc iodide
Cadmium iodide
Related compounds
Mercury(I) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Mercury(II) iodide is a chemical compound with the molecular formula HgI2. It is typically produced synthetically but can also be found in nature as the extremely rare mineral coccinite. Unlike the related mercury(II) chloride it is hardly soluble in water (<100 ppm).

Production

Mercury(II) iodide is produced by adding an aqueous solution of potassium iodide to an aqueous solution of mercury(II) chloride with stirring; the precipitate is filtered off, washed and dried at 70 °C.

HgCl2 + 2 KI → HgI2 + 2 KCl

Properties

Mercury(II) iodide displays thermochromism; when heated above 126 °C (400 K) it undergoes a phase transition, from the red alpha crystalline form to a pale yellow beta form. As the sample cools, it gradually reacquires its original colour. It has often been used for thermochromism demonstrations.[2] A third form, which is orange, is also known; this can be formed by recrystallisation and is also metastable, eventually converting back to the red alpha form.[3] The various forms can exist in a diverse range of crystal structures and as a result mercury(II) iodide possesses a surprisingly complex phase diagram.[4]

Uses

Mercury(II) iodide crystals grown in Spacelab

Mercury(II) iodide is used for preparation of Nessler's reagent, used for detection of presence of ammonia.

Mercury(II) iodide is a semiconductor material,[5] used in some x-ray and gamma ray detection and imaging devices operating at room temperatures.[6]

In veterinary medicine, mercury(II) iodide is used in blister ointments in exostoses, bursal enlargement, etc. [citation needed]

It can appear as a precipitate in many reactions.

See also

References

  1. John Rumble (June 18, 2018) (in English). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN 978-1138561632. 
  2. Thermochromism: Mercury(II) Iodide. Jchemed.chem.wisc.edu. Retrieved on 2011-06-02.
  3. SCHWARZENBACH, D. (1 January 1969). "The crystal structure and one-dimensional disorder of the orange modification of HgI2". Zeitschrift für Kristallographie - Crystalline Materials 128 (1–6): 97–114. doi:10.1524/zkri.1969.128.16.97. 
  4. Hostettler, Marc; Schwarzenbach, Dieter (February 2005). "Phase diagrams and structures of HgX2 (X = I, Br, Cl, F)". Comptes Rendus Chimie 8 (2): 147–156. doi:10.1016/j.crci.2004.06.006. https://comptes-rendus.academie-sciences.fr/chimie/articles/10.1016/j.crci.2004.06.006/. 
  5. Ayres, F.; Assali, L.V. C.; Machado, W. V. M.; Justo, J. F. (2006). "Role of intrinsic defects in the electronic and optical properties of alpha-HgI2". Appl. Phys. Lett. 88: 011918. doi:10.1063/1.2159573. 
  6. Simage, Oy U.S. Patent 6,509,203 Semiconductor imaging device and method for producing same, Issue date: Jan 21, 2003
HI He
LiI BeI2 BI3 CI4 NI3 I2O4,
I2O5,
I4O9
IF,
IF3,
IF5,
IF7
Ne
NaI MgI2 AlI3 SiI4 PI3,
P2I4
S ICl,
ICl3
Ar
KI CaI2 Sc TiI4 VI3 CrI3 MnI2 FeI2 CoI2 NiI2 CuI ZnI2 Ga2I6 GeI2,
GeI4
AsI3 Se IBr Kr
RbI SrI2 YI3 ZrI4 NbI5 Mo Tc Ru Rh Pd AgI CdI2 InI3 SnI4,
SnI2
SbI3 TeI4 I Xe
CsI BaI2   HfI4 TaI5 W Re Os Ir Pt AuI Hg2I2,
HgI2
TlI PbI2 BiI3 Po AtI Rn
Fr RaI2   Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
La Ce Pr Nd Pm SmI2 Eu Gd TbI3 Dy Ho Er Tm Yb Lu
Ac ThI4 Pa UI3,
UI4
Np Pu Am Cm Bk Cf EsI3 Fm Md No Lr