Mercury(II) Sulfide

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Mercury(II) Sulfide

OVERVIEW

Mercury(II) sulfide (MER-kyuh-ree two SUL-fide) occurs in two forms, red and black. Red mercury(II) sulfide, commonly known as cinnabar, begins to change color when heated to temperatures of about 250°C (500°F) and converts to the black form at 386°C (727°F). If heated further, it sublimes (changes directly from a solid to a gas without first melting) at 583.5°C (1,082°F). If allowed to cool, it then reverts to its original reddish color. Black mercury(II) sulfide goes through a similar process, changing to its red counterpart before melting at 583.5°C (1,082°F). Some authoritative resources give significantly different temperatures for these transitions. Red mercury(II) sulfide occurs naturally as the mineral cinnabar, while black mercury(II) sulfide occurs only rarely in nature, then as the mineral metacinnabar (meaning "similar to cinnabar").

KEY FACTS

OTHER NAMES:

Mercuric sulfide; cinnabar; vermillion; Chinese red

FORMULA:

HgS

ELEMENTS:

Mercury, sulfur

COMPOUND TYPE:

Inorganic salt

STATE:

Solid

MOLECULAR WEIGHT:

232.66 g/mol

MELTING POINT:

Data differ significantly; see Overview

BOILING POINT:

Not applicable

SOLUBILITY:

Insoluble in water, alcohol, and most acids; soluble in aqua regia

HOW IT IS MADE

Red mercury(II) sulfide is obtained commercially from the mineral cinnabar. The compound can also be made synthetically by heating mercury and sulfur together in a gaseous state or by heating mercury with a solution of potassium pentasulfide (K₂S₅). The compound produced by either of these methods is commonly known as English vermillion, or simply, vermillion. The term vermillion is generally reserved for any form of mercury(II) sulfide that has been made synthetically rather than extracted from cinnabar. Other methods for the preparation of both red and black mercury(II) sulfide are available. For example, the black form can be produced by reacting sodium thiosulfate (Na₂S₂O₃) with sodium mercurichloride (Na₂HgCl₄).

COMMON USES AND POTENTIAL HAZARDS

The earliest records of the use of mercury(II) sulfide by humans date to about the third millennium BCE in China, where the compound was used to cure diseases, relieve pain, as a narcotic and an antiseptic, and as a preservative. Chinese alchemists referred to the compound as "celestial sands" or "god's sand" and believed that it could transform base metals, like iron and lead, into precious metals, like silver and gold.

Today, the primary use of mercury(II) sulfide is in the production of metallic mercury. The sulfide is heated in a furnace to temperatures of 600°C to 700°C (1,100°F to 1,300°F), resulting in the formation of sulfur dioxide and mercury metal. In a second process, the sulfide is treated with lime (CaO), resulting in the formation of mercury metal, calcium sulfide (CaS) and calcium sulfate (CaSO₄).

The other major use for mercury(II) sulfide, in either red or black form, is as a pigment in artists' paints, for coloring paper and plastics, and for marking linen. The black form is also used as a pigment for the coloring of rubber, horn, and other materials. Red mercury(II) sulfide finds some use also as an antibacterial agent.

Interesting Facts

Women used vermillion during the Renaissance period to redden their lips and cheeks.
Mercury(II) sulfide is a comparatively expensive compound, selling in late 2005 for about 1,600 dollars per 100 grams.

Words to Know

ALCHEMY: An ancient field of study from which the modern science of chemistry evolved.
AQUA REGIA: A combination of concentrated nitric acid and hydrochloric acid.

Both forms of mercury(II) sulfide are highly toxic by ingestion, inhalation, or absorption through the skin. Some of the symptoms resulting from mercury(II) sulfide poisoning include inflammation and itching of the skin; redness, itching, burning, and watering of the eyes; excessive salivation; pain when chewing; gingivitis with loosening of teeth; and mental disturbances, such as loss of memory, insomnia, irritability, and vague fears of depression. Anyone who has been exposed to mercury(II) sulfide and experiences such symptoms requires immediate medical attention.