Mercury(II) iodide

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Mercury(II) iodide
Mercury(II) iodide (α form)
Mercury(II) iodide (β form)
Mercury iodide.jpg
β (left) and α (right) forms
IUPAC name
Mercury diiodide
Other names
Mercuric iodide
Red mercury (α form only)
3D model (JSmol)
ECHA InfoCard 100.028.976
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
Solubility slightly soluble in alcohol, ether, acetone, chloroform, ethyl acetate, CS2, olive oil, castor oil
−128.6·10−6 cm3/mol
D08AK30 (WHO)
Very toxic (T+)
Dangerous for the environment (N)
R-phrases (outdated) R26/27/28, R33, R50/53
S-phrases (outdated) (S1/2), S13, S28, S45, S60, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
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).
N verify (what is YesYN ?)
Infobox references

Mercury(II) iodide (HgI2) is a chemical compound with an appearance of red-orange crystals. Unlike mercury(II) chloride it is hardly soluble in water (<100 ppm).

Conditions/substances to avoid include: heat, light, bromides, chlorides, ammonia, alkalis, cyanides, copper salts, lead salts, iodoform and hydrogen peroxide.


Mercury(II) iodide displays thermochromism; when heated above 126 °C, it undergoes phase transition from the alpha crystalline form to a pale yellow beta form. As the sample cools, it gradually reacquires its original color. It is often used for thermochromism demonstrations.[1]


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.


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, used in some x-ray and gamma ray detection and imaging devices operating at room temperatures.[2]

Mercury(II) iodide can be found extremely rarely in nature as mineral coccinite.

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[edit]


  1. ^ Thermochromism: Mercury(II) Iodide. Retrieved on 2011-06-02.
  2. ^ Simage, Oy U.S. Patent 6,509,203 Semiconductor imaging device and method for producing same, Issue date: Jan 21, 2003