About Mercury sulfide

Mercury sulfide (English name: Mercury (II) Sulfide) is an inorganic compound with a chemical formula of HgS and a molecular weight of 232.65. Mercury sulfide has a stable red (α-type) appearance and an unstable black (β-type) appearance. The density of black mercury sulfide is 7.55~7.7g/cm3, and the density of red mercury sulfide, also known as cinnabar, cinnabar, and silver vermilion, is 8.06~8.12g/cm3. Black mercury sulfide can be converted into red mercury sulfide by heating and sublimation. Mercury sulfide has a melting point of 583℃ and is insoluble in water, dilute acid, alcohol and other organic solvents. It is soluble in solutions of sodium sulfide, potassium thiocyanate, potassium chlorate and potassium iodide. It can also be soluble in hot sulfuric acid, hot nitric acid, hot hydrochloric acid and aqua regia . Mercury sulfide can be decomposed into elemental mercury and elemental sulfur by heating without air. When heated, it reacts with simple substances such as oxygen to produce mercuric oxide and sulfur dioxide, reacts with chlorine to produce mercuric chloride and elemental sulfur, reacts with iron to produce elemental mercury and ferrous sulfide, and heats with oxides such as calcium oxide to produce elemental mercury and calcium sulfide .
There are two methods for synthesizing mercuric sulfide. One is to add excess sodium sulfide or ammonium sulfide to a mercuric chloride aqueous solution and boil it in an acidic environment to produce black mercuric sulfide, which is then sublimated to produce red mercuric sulfide. The other is to heat mercury and sulfur in a vacuum to above 240°C, cool and remove the unreacted products to produce mercuric sulfide . Mercury sulfide can be used as a traditional Chinese medicine preparation, as well as vermilion lacquer and red pigment for painting. It can also be used in colored sealing wax, plastics, rubber and textiles . Natural mercuric sulfide is the main raw material for manufacturing mercury .
Mercury sulfide is irritating to the eyes and is toxic by inhalation, skin contact and accidental swallowing. Mercury sulfide is extremely toxic to aquatic organisms and may cause long-term adverse effects on the aquatic environment.

 

The chemical equation for HgS dissolved in aqua regia is: 3HgS +2 HNO3 + 12HCl = 3H2[HgCl4] + 3S + 2NO + 4H2O.
The chemical equation for HgS dissolved in concentrated hydroiodic acid is: HgS + 4HI = H2S + H2[HgI4]
HgS is a twin crystal, as follows:
Red cinnabar (α-HgS), its structure is the most common form of mercury in nature. Black cinnabar (β-HgS), is uncommon in nature and has a sphalerite (cubic ZnS) crystal structure.
Red crystals, α-HgS is optically active. This is because Hg-S is arranged in a spiral in the structure. At 300°K, with an energy gap of 2.1eV, α-HgS is a direct semiconductor.
α-HgS was used as a vermilion pigment when it was discovered. After the 21st century, it was known that cinnabar turned dark red because it changed from red α-HgS to black β-HgS. The red walls of Pompeii were black when they were unearthed because mercury chloride compounds (such as chlorothiomercurite, calomel, yellow chloromercurite), calcium sulfate and gypsum had been formed, but β-HgS was not detected.
α and β types of mercuric sulfide reach equilibrium at 360°C. When the temperature exceeds 410°C, the α type quickly converts to the β type, but the β type can remain unchanged for a long time at room temperature. It does not react with most acids, but dissolves in concentrated hydrobromic acid and hydroiodic acid to form corresponding halides. HgS can be dissolved in solutions of alkali metal sulfides. Black mercuric sulfide is unlikely to be converted into red mercuric sulfide when heated and sublimated directly in the air. Instead, the sulfur in the mercuric sulfide will burn and make the entire black mercuric sulfide hard.

Mercury sulfide is the main raw material for manufacturing mercury. It is also used as a red pigment in raw lacquer, ink, seal oil, vermilion carved lacquerware and paintings, as well as in colored sealing wax, plastics, rubber, medicine and preservatives.