Rubbing alcohol

Rubbing alcohol is either an isopropyl alcohol or an ethanol-based liquid, with isopropyl alcohol products being the most widely available. The comparable British Pharmacopoeia (BP) is surgical spirit. Rubbing alcohol is denatured and undrinkable even if it is ethanol-based, due to the bitterants added.

A bottle of isopropyl rubbing alcohol

They are liquids used primarily as a topical antiseptic.[1] They also have multiple industrial and household applications.[2][3] The term "rubbing alcohol" in North American English is a general term for either isopropyl alcohol (isopropanol) or ethyl alcohol (ethanol) products.

The United States Pharmacopeia (USP) defines "isopropyl rubbing alcohol USP" as containing approximately 70 percent alcohol by volume of pure isopropyl alcohol and defines "rubbing alcohol USP" as containing approximately 70 percent by volume of denatured alcohol.[4][5] In Ireland and the UK, the comparable preparation is surgical spirit B.P., which the British Pharmacopoeia defines as 95% methylated spirit, 2.5% castor oil, 2% diethyl phthalate, and 0.5% methyl salicylate.[6] Under its alternative name of "wintergreen oil", methyl salicylate is a common additive to North American rubbing alcohol products.[7] Individual manufacturers are permitted to use their own formulation standards in which the ethanol content for retail bottles of rubbing alcohol is labeled as and ranges from 70 to 99% v/v.[8]

All rubbing alcohols are unsafe for human consumption: isopropyl rubbing alcohols do not contain the ethyl alcohol of alcoholic beverages; ethyl rubbing alcohols are based on denatured alcohol, which is a combination of ethyl alcohol and one or more bitter poisons that make the substance toxic.

History

The term "rubbing alcohol" came into prominence in North America in the mid-1920s. The original rubbing alcohol was literally used as a liniment for massage; hence the name. This original rubbing alcohol was rather different from today's precisely formulated surgical spirit; in some formulations it was perfumed and included different additives, notably a higher concentration of methyl salicylate.

The name "rubbing" also emphasized that the alcohol was not intended for consumption, a significant distinction in Prohibition-era America; nonetheless it had become a well-documented surrogate alcohol as early as 1925.

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).[9] Surgical spirit BP boils at 80 °C (176 °F).[10]

Naturally colorless, products may contain color additives. They may also contain medically-inactive additives for fragrance, such as wintergreen oil (methyl salicylate),[11] or for other purposes.

US legislation
Main article: Denatured alcohol

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.[12]

Warnings

Product labels for rubbing alcohol include a number of warnings 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. [13][14]

References
  1. "Surgical Spirit meaning". Cambridge University Press. Retrieved 21 January 2016.
  2. "Alcohols, phenols, and ethers". University of Nebraska–Lincoln. Britannica.com. Retrieved 22 January 2016.
  3. "12 Ways to Use Rubbing Alcohol". Reader's digest. Archived from the original on 29 January 2016. Retrieved 22 January 2016.
  4. "Isopropyl Rubbing Alcohol, chemical structure, molecular formula, Reference Standards". newdruginfo.com. United States Pharmacopeia. Retrieved 22 January 2016.
  5. "Rubbing Alcohol, chemical structure, molecular formula, Reference Standards". newdruginfo.com. United States Pharmacopeia. Retrieved 22 January 2016.
  6. "Surgical Spirit, BP". British National Formulary. Archived from the original on 11 May 2012. Retrieved 21 January 2016.
  7. "'rubbing alcohol' wintergreen – search results". Drugs.com. Retrieved 22 January 2016.
  8. Wilson, Charles; John H. Block; Ole Gisvold; John Marlowe Beale (2004). "8". Wilson and Gisvold's textbook of organic medicinal and pharmaceutical chemistry (11 ed.). Lippincott Williams & Wilkins. p. 219. ISBN 978-0-7817-3481-3.
  9. "Isopropyl alcohol 50%" (PDF). National Radio Astronomy Observatory. Retrieved 22 January 2016.
  10. "Surgical Spirit BP Safety Data Sheet" (PDF). Chemtek Limited. Retrieved 22 January 2016.
  11. "1993 MUACC Analytical Chemistry Laboratory Experiments" (PDF). University of Minnesota. p. 83. Retrieved 22 January 2016.
  12. Expert Committee:(PA2)Pharmaceutical Analysis 2, USP28–NF23 Page 62, Pharmacopeial Forum:Volume No.27(3)Page 2507
  13. DeBellonia RR, Marcus S, Shih R, Kashani J, Rella JG, Ruck B (April 2008). "Curanderismo: consequences of folk medicine". Pediatr Emerg Care. 24 (4): 228–9. doi:10.1097/PEC.0b013e31816b7a92. PMID 18418260. S2CID 45598242.
  14. Trullas JC, Aguilo S, Castro P, Nogue S (October 2004). "Life-threatening isopropyl alcohol intoxication: is hemodialysis really necessary?". Vet Hum Toxicol. 46 (5): 282–4. PMID 15487656.
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