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chemistry

Smelling salts

Smelling salts 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 Smelling salts rather than just read about it. In short: Smelling salts, also known as ammonia inhalants, spirit of hartshorn, or sal volatile, are chemical compounds used as stimulants to restore consciousness after fainting. The usual active compound is ammonium carbonate—a colorless-to-white, crystalline solid ((NH4)2CO3).

Smelling salts — main illustration
Smelling salts — illustration

Key takeaways

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

Reference excerpt

Smelling salts, also known as ammonia inhalants, spirit of hartshorn, or sal volatile, are chemical compounds used as stimulants to restore consciousness after fainting. The usual active compound is ammonium carbonate—a colorless-to-white, crystalline solid ((NH4)2CO3). Since most modern solutions are mixed with water, they may also be called aromatic spirits of ammonia. Modern solutions may also contain other products to perfume or act in conjunction with the ammonia, such as lavender oil or eucalyptus oil.

Use Historically, smelling salts have been used on people feeling faint, or who have fainted. Others usually administer them, but they may also be self-administered. Smelling salts are often used on athletes who have been dazed or knocked unconscious to restore consciousness and mental alertness. Smelling salts are now banned in most boxing competitions because of the concern that their effect could mask a more serious injury. They are also used as a form of stimulant in athletic competitions (such as powerlifting, strong man, rugby, and ice hockey) to "wake up" competitors to perform better. In 2005, Michael Strahan estimated that 70–80% of NFL players were using smelling salts as stimulants.

History

Smelling salts have been used since Roman times and are mentioned in the writings of Pliny as Hammoniacus sal. Evidence exists of use in the 13th century by alchemists as sal ammoniac. In the 14th-century "The Canon's Yeoman's Tale", one of Chaucer's The Canterbury Tales, an alchemist purports to use sal armonyak. In the 17th century, the distillation of an ammonia solution from shavings of harts' (deer) horns and hooves led to the alternative name for smelling salts as spirit or salt of hartshorn. They were widely used in Victorian Britain to revive fainting women, and in some areas, constables would carry a container of them for that purpose. At that time, smelling salts were commonly dissolved with perfume in vinegar or alcohol and soaked onto a sponge, which was then carried on the person in a decorative container called a vinaigrette. The sal volatile appears several times in Dickens' novel Nicholas Nickleby. The use of smelling salts was widely recommended during the World War II, with all workplaces advised by the British Red Cross and St. John Ambulance to keep smelling salts in their first aid boxes.

Physiological action

Solid ammonium carbonate and ammonium bicarbonate salts partly dissociate to form NH3, CO2 and H2O vapour as follows:

The smelling salts release ammonia (NH3) gas, which triggers an inhalation reflex. It causes the muscles that control breathing to work faster by irritating the mucous membranes of the nose and lungs. Fainting can be caused by excessive parasympathetic and vagal activity that slows the heart and decreases perfusion of the brain. The sympathetic irritant effect is exploited to counter the vagal parasympathetic effects and thereby reverse the faint.

Risks Exposure to ammonia gas in large concentrations for prolonged periods is toxic and can be fatal. If a high concentration of ammonia is inhaled too close to the nostril, it might burn the nasal or oral mucosa. The suggested distance is 10–15 centimetres (4–6 in). The use of ammonia smelling salts to revive people injured during sport is not recommended because it may inhibit or delay a proper and thorough neurological assessment by a healthcare professional, such as after concussions when hospitalization may be advisable, and some governing bodies recommend specifically against it. The irritant nature of smelling salts means that they can exacerbate any pre-existing cervical spine injury by causing reflex withdrawal away from them, although this is a result of holding the smelling salts closer to the nose than recommended. The National Football League banned teams from providing smelling salts to players in 2025, though the use of smelling salts itself was still permitted.

References

External links "'Vaporole' smelling salts, London, England, 1924-1940". Science Museum Group. Retrieved 9 October 2025.

Illustrations

Smelling salts: Two capsules of smelling salts from a first-aid kit. A thin inner glass tube contains alcohol and ammonia; the outer layer is cotton and netting. When crushed, the liquid is released into the cotton, while the glass shards are retained inside. The ammonia-soaked cotton is waved in front of the nose for the treatment of fainting.
Two capsules of smelling salts from a first-aid kit. A thin inner glass tube contains alcohol and ammonia; the outer layer is cotton and netting. When crushed, the liquid is released into the cotton, while the glass shards are retained inside. The ammonia-soaked cotton is waved in front of the nose for the treatment of fainting.
Smelling salts: Flask with smelling salts, used for reviving dental patients after a procedure; French, 18th century
Flask with smelling salts, used for reviving dental patients after a procedure; French, 18th century
Smelling salts: Rembrandt's Unconscious Patient (Allegory of Smell) shows a woman using smelling salts to revive a man who has fainted at the hands of a barber-surgeon.
Rembrandt's Unconscious Patient (Allegory of Smell) shows a woman using smelling salts to revive a man who has fainted at the hands of a barber-surgeon.

Worked examples

Example 1 — a first encounter with Smelling salts

Start with the simplest possible case. Write down what Smelling salts 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 Smelling salts 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 Smelling salts 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 Smelling salts

In research
Smelling salts 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 Smelling salts 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
Smelling salts is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ammonium compounds, First aid, Odor, so understanding it makes those chapters shorter.
In everyday life
Look for Smelling salts 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 Smelling salts in 20 minutes

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

Frequently asked questions

What is Smelling salts in simple terms?

Smelling salts, also known as ammonia inhalants, spirit of hartshorn, or sal volatile, are chemical compounds used as stimulants to restore consciousness after fainting. The usual active compound is ammonium carbonate—a colorless-to-white, crystalline solid ((NH4)2CO3).

Why does Smelling salts 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 Smelling salts?

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 Smelling salts.

Tags

  • Ammonium compounds
  • First aid
  • Odor

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