Mercury sulfide

This article is about the mercuric salt. For the hypothesized mercurous salt, see mercury(I) sulfide.

Mercury sulfide, or mercury(II) sulfide is a chemical compound composed of the chemical elements mercury and sulfur. It is represented by the chemical formula HgS. It is virtually insoluble in water.^[4]

Mercury sulfide

Names
IUPAC name Mercury sulfide
Other names Cinnabar Vermilion
Identifiers
CAS Number	1344-48-5 Y
3D model (JSmol)	Interactive image
ChemSpider	8395759
ECHA InfoCard	100.014.270
EC Number	215-696-3
PubChem CID	62402
UNII	ZI0T668SF1 Y
UN number	2025
CompTox Dashboard (EPA)	DTXSID301318265 DTXSID0047747, DTXSID301318265
InChI InChI=1S/Hg.S Key: QXKXDIKCIPXUPL-UHFFFAOYSA-N
SMILES [S]=[Hg]
Properties
Chemical formula	HgS
Molar mass	232.66 g/mol
Density	8.10 g/cm3
Melting point	580 °C (1,076 °F; 853 K) decomposes
Solubility in water	insoluble
Band gap	2.1 eV (direct, α-HgS) [1]
Magnetic susceptibility (χ)	−55.4·10−6 cm3/mol
Refractive index (nD)	w=2.905, e=3.256, bire=0.3510 (α-HgS) [2]
Thermochemistry
Std molar entropy (S⦵298)	78 J·mol−1·K−1[3]
Std enthalpy of formation (ΔfH⦵298)	−58 kJ·mol−1[3]
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H310, H317, H330, H373, H410
Precautionary statements	P261, P272, P280, P302+P352, P321, P333+P313, P363, P501
NFPA 704 (fire diamond)	4 0 0
Flash point	Non-flammable
Safety data sheet (SDS)	Fisher Scientific
Related compounds
Other anions	Mercury oxide mercury selenide mercury telluride
Other cations	Zinc sulfide cadmium sulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Crystal structure

Structure of a-HgS looking at the a-axis

Structure of a-HgS looking at the c-axis

HgS is dimorphic with two crystal forms:

• red cinnabar (α-HgS, trigonal, hP6, P3221) is the form in which mercury is most commonly found in nature. Cinnabar has rhombohedral crystal system. Crystals of red are optically active. This is caused by the Hg-S helices in the structure.^[5]
• black metacinnabar (β-HgS) is less common in nature and adopts the zinc blende crystal structure (T²_d-F43m).

Preparation and chemistry

β-HgS precipitates as a black solid when Hg(II) salts are treated with H₂S. The reaction is conveniently conducted with an acetic acid solution of mercury(II) acetate. With gentle heating of the slurry, the black polymorph converts to the red form.^[6] β-HgS is unreactive to all but concentrated acids.^[4]

Mercury is produced from the cinnabar ore by roasting in air and condensing the vapour.^[4]

HgS → Hg + S

Uses

Cinnabar (red portion of specimen)

When α-HgS is used as a red pigment, it is known as cinnabar. The tendency of cinnabar to darken has been ascribed to conversion from red α-HgS to black β-HgS. However β-HgS was not detected at excavations in Pompeii, where originally red walls darkened, and was attributed to the formation of Hg-Cl compounds (e.g., corderoite, calomel, and terlinguaite) and calcium sulfate, gypsum.^[7]

As the mercury cell as used in the chlor-alkali industry (Castner–Kellner process) is being phased out over concerns over mercury emissions, the metallic mercury from these setups is converted into mercury sulfide for underground storage.

With a band gap of 2.1 eV and its stability, it is possible to be used as photoelectrochemical cell.^[8]

Neutralization with sulfur has been suggested to clean mercury spills, but the reaction does not proceed rapidly and completely enough for emergencies.^[9]

See also

• Mercury poisoning
• Mercury(I) sulfide (mercurous sulfide, Hg
  ₂S), hypothetical