My watch list  

Mercury(II) iodide

Mercury(II) iodide
Other names mercuric iodide
mercury biniodide
CAS number 7774-29-0
Molecular formula HgI2
Molar mass 454.40 g/mol
Appearance scarlet red powder
Density 6.36 g/cm³, solid
Melting point


Boiling point

350°C (sublimes)

Solubility in water 6mg/100g water
NFPA 704
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and 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 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]

In medicine, mercury(II) iodide was formerly used as a treatment for syphilis.

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

Mercury(II) iodide is one of the stated possibilities for the "red mercury".

See also

  • Mercury(I) iodide


    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Mercury(II)_iodide". A list of authors is available in Wikipedia.
    Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE