Characteristic

Mercury sulfide, mercuric sulfide, mercury sulphide, or mercury(II) sulfide is a chemical compound composed of the chemical elements mercury and sulfur.

Chemical formula：HgS

CAS#:1344-48-5

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)

Magnetic susceptibility (χ)：−55.4·10⁻⁶ cm³/mol

Refractive index (nD)：w=2.905, e=3.256, bire=0.3510 (α-HgS)

Application

When α-HgS is used as a red pigment, it is known as vermilion. The tendency of vermilion 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.