chemistry

Rubbing alcohol

Rubbing alcohol 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 Rubbing alcohol rather than just read about it. In short: Rubbing alcohol, known as surgical spirit in the British Pharmacopoeia, refers to a group of denatured alcohol solutions commonly used as topical disinfectant. In addition to its medical applications, rubbing alcohol is employed in various industrial and household contexts.

Key takeaways

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

Reference excerpt

Rubbing alcohol, known as surgical spirit in the British Pharmacopoeia, refers to a group of denatured alcohol solutions commonly used as topical disinfectant. In addition to its medical applications, rubbing alcohol is employed in various industrial and household contexts. These solutions are primarily composed of either isopropyl alcohol (isopropanol) or ethanol, with isopropyl alcohol being the more widely available formulation. The United States Pharmacopeia (USP) defines "isopropyl rubbing alcohol USP" as a solution containing approximately 70% alcohol by volume of pure isopropanol, while "rubbing alcohol USP" refers to a solution containing approximately 70% by volume of denatured ethanol. In Ireland and the United Kingdom, the comparable product is "surgical spirit B.P.", defined by the British Pharmacopoeia as containing 95% methylated spirit, 2.5% castor oil, 2% diethyl phthalate, and 0.5% methyl salicylate. Known alternatively as "wintergreen oil", methyl salicylate is also a common additive in North American rubbing alcohol products. Manufacturers are permitted to use their own formulations, and retail rubbing alcohol typically contains between 70% and 99% alcohol by volume, depending on the specific product and intended use. Rubbing alcohol is unsafe for human consumption. Isopropyl rubbing alcohol does not contain the ethyl alcohol found in alcoholic beverages, and even ethanol-based rubbing alcohol often contains substances that are toxic when ingested. For this reason, most rubbing alcohol contains a bitterant which serve to make it undrinkable and prevent misuse.

History The term rubbing alcohol came into prominence in North America during the Prohibition era of 1920 to 1933, when alcoholic beverages were prohibited throughout the United States. The term rubbing emphasized that this alcohol was not intended for consumption. Nevertheless it was well documented as a surrogate alcohol as early as 1925. Alcohol was already widely used as a liniment for massage. There was no standard formula for rubbing alcohol, which was sometimes perfumed with additives such as wintergreen oil (methyl salicylate).

Properties All rubbing alcohols are volatile and flammable. Ethyl rubbing alcohol has an extremely bitter taste from additives. The specific gravity of Formula 23-H is between 0.8691 and 0.8771 at 15.56 °C (60.01 °F). Isopropyl rubbing alcohols contain from 50% to 99% by volume of isopropyl alcohol, the remainder consisting of water. Boiling points vary with the proportion of isopropyl alcohol from 80 to 83 °C (176 to 181 °F); likewise, freezing points vary from −32 to −50 °C (−26 to −58 °F). Surgical spirit BP boils at 80 °C (176 °F). Naturally colorless, products may contain color additives. They may also contain medically-inactive additives for fragrance, such as wintergreen oil (methyl salicylate), or for other purposes.

US legislation

To protect alcohol tax revenue in the United States, all preparations classified as Rubbing Alcohols (defined as those containing ethanol) must have poisonous additives to limit human consumption in accordance with the requirements of the US Treasury Department, Bureau of Alcohol, Tobacco, and Firearms, using Formula 23-H (8 parts by volume of acetone, 1.5 parts by volume of methyl isobutyl ketone, and 100 parts by volume of ethyl alcohol). It contains 87.5–91% by volume of absolute ethyl alcohol. The rest consists of water and the denaturants, with or without color additives, and perfume oils. Rubbing alcohol contains in each 100 ml more than 355 mg of sucrose octaacetate or more than 1.40 mg of denatonium benzoate. The preparation may be colored with one or more color additives. A suitable stabilizer may also be added.

Warnings

Product labels for rubbing alcohol include a number of hazard symbols about the chemical, including the flammability hazards and its intended use only as a topical antiseptic and not for internal wounds or consumption. It should be used in a well-ventilated area due to inhalation hazards. Poisoning can occur from ingestion, inhalation, absorption, or consumption of rubbing alcohol.

References

See also Methanol Aminomethanol Methanol (data page) Methanol economy Trimethyl carbinol

External links Why Is Drinking Rubbing Alcohol Bad?

Illustrations

Worked examples

Example 1 — a first encounter with Rubbing alcohol

Start with the simplest possible case. Write down what Rubbing alcohol 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 Rubbing alcohol 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 Rubbing alcohol 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 Rubbing alcohol

In research: Rubbing alcohol 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 Rubbing alcohol 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: Rubbing alcohol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antiseptics, Cleaning products, Household chemicals, so understanding it makes those chapters shorter.
In everyday life: Look for Rubbing alcohol 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 Rubbing alcohol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rubbing alcohol 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 Rubbing alcohol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rubbing alcohol in simple terms?

Why does Rubbing alcohol 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 Rubbing alcohol?

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 Rubbing alcohol.