chemistry

Mercury sulfide

Mercury sulfide is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mercury sulfide rather than just read about it. In short: 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.

Key takeaways

Mercury sulfide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mercury sulfide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mercury sulfide from memory before moving on to harder problems.

Reference excerpt

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.

Crystal structure

HgS is dimorphic with two crystal forms:

Red cinnabar (α-HgS) is the form in which mercury is most commonly found in nature. Cinnabar has a rhombohedral crystal system. Crystals of α-HgS are optically active. This is caused by helices in the structure. Black metacinnabar (β-HgS) is less common in nature and adopts the zinc blende crystal structure (T2d-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. β-HgS is unreactive to all but concentrated acids. Mercury is produced from the cinnabar ore by roasting in air and condensing the vapour.

HgS → Hg + S

Uses

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. 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. It has been studied for use in photoelectrochemical cells.

See also Mercury poisoning Mercury(I) sulfide (mercurous sulfide, Hg2S), hypothetical

References

Illustrations

Worked examples

Example 1 — a first encounter with Mercury sulfide

Start with the simplest possible case. Write down what Mercury sulfide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mercury sulfide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mercury sulfide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mercury sulfide

In research: Mercury sulfide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mercury sulfide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mercury sulfide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Mercury(II) compounds, Monosulfides, Zincblende crystal structure, so understanding it makes those chapters shorter.
In everyday life: Look for Mercury sulfide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Mercury sulfide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mercury sulfide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mercury sulfide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mercury sulfide in simple terms?

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.

Why does Mercury sulfide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mercury sulfide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mercury sulfide.