-iodide-xtal-3D-SF-A.png) Mercury(II) iodide (α form) | |
-iodide-xtal-3D-SF-B.png) Mercury(II) iodide (β form) | |
 β (left) and α (right) forms | |
| Names | |
|---|---|
| IUPAC name Mercury(II) iodide | |
| Other names | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
|
| DrugBank |
|
| ECHA InfoCard | 100.028.976 |
| EC Number |
|
| 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) |
| 6 mg/100 mL | |
Solubility product (Ksp) | 2.9×10−29[1] |
| Solubility | slightly soluble inalcohol,ether,acetone,chloroform,ethyl acetate,CS2,olive oil,castor oil Soluble in excess KI(Potassium iodide) forming soluble complex K2[HgI4 ](Potassium tetraiodomercurate(II)) also known asNessler's reagent |
| −128.6·10−6 cm3/mol | |
Refractive index (nD) | 2.455 |
| Structure | |
| Tetrahedral | |
| Pharmacology | |
| D08AK30 (WHO) | |
| Hazards | |
| GHS labelling: | |
   | |
| Danger | |
| H300,H310,H330,H373,H410 | |
| P260,P262,P264,P270,P271,P273,P280,P284,P301+P310,P302+P350,P304+P340,P310,P314,P320,P321,P322,P330,P361,P363,P391,P403+P233,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Otheranions | Mercury(II) fluoride Mercury(II) chloride Mercury(II) bromide |
Othercations | Zinc iodide Cadmium iodide |
Related compounds | Mercury(I) iodide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Mercury(II) iodide is achemical compound with the molecular formulaHgI2. It is typically produced synthetically but can also be found in nature as the extremely rare mineralcoccinite. Unlike the relatedmercury(II) chloride it is hardly soluble in water (<100 ppm).
Mercury(II) iodide is produced by adding an aqueous solution ofpotassium iodide to an aqueous solution ofmercury(II) chloride with stirring; the precipitate is filtered off, washed and dried at 70 °C.
Mercury(II) iodide displaysthermochromism; when heated above 127 °C (400 K) it undergoes aphase 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 forthermochromism demonstrations.[2] A third form, which is orange, is also known; this can be formed by recrystallisation and is alsometastable, 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 complexphase diagram.[4]
Mercury(II) iodide is used for preparation ofNessler's reagent, used for detection of presence ofammonia.
Mercury(II) iodide is asemiconductor material, used in somex-ray andgamma ray detection and imaging devices operating at room temperatures.[5]
Inveterinary medicine, mercury(II) iodide is used inblisterointments inexostoses,bursal enlargement, etc.[citation needed]
It can appear as a precipitate in many reactions.
