Mercury(II) iodide

Mercury(II) iodide
	Mercury(II) iodide (α form)
	Mercury(II) iodide (β form)
	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
CAS Number	7774-29-0 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:49659 ;
ChemSpider	22893 ;
DrugBank	DB04445 ;
ECHA InfoCard	100.028.976
EC Number	231-873-8;
Gmelin Reference	277788
PubChem CID	24485;
UNII	R03O05RB0P ;
CompTox Dashboard (EPA)	DTXSID9042124 ;
	InChI InChI=1S/Hg.2HI/h;21H/q+2;;/p-2 Key: YFDLHELOZYVNJE-UHFFFAOYSA-L ; InChI=1/Hg.2HI/h;21H/q+2;;/p-2 Key: YFDLHELOZYVNJE-NUQVWONBAE;
	SMILES I[Hg]I;
Properties
Chemical formula	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)
Solubility in water	6 mg/100 mL
Solubility product (Ksp)	2.9×10−29
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[HgI4 ](Potassium tetraiodomercurate(II)) also known as Nessler's reagent
Magnetic susceptibility (χ)	−128.6·10−6 cm3/mol
Refractive index (nD)	2.455
Structure
Crystal structure	Tetrahedral
Pharmacology
ATC code	D08AK30 (WHO)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H310, H330, H373, H410
Precautionary statements	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)	3 0 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). verify (what is ?) Infobox references

Mercury(II) iodide is a chemical compound with the molecular formula Hg I₂. 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).