What Is Denatured Alcohol?


Denatured alcohol is ethanol that has been made unsuitable for drinking.
Denatured alcohol is ethanol that has been made unsuitable for drinking. (photo: Martin Lopez)

Denatured alcohol is ethanol (ethyl alcohol or grain alcohol) made unfit for human consumption by adding chemicals called denaturants. It is also called denatured rectified spirit or methylated spirits. In general, denaturing removes a property from a substance without chemically altering it. In the case of denatured alcohol, denaturing makes the alcohol taste bad or else too toxic to drink.

Why Is Alcohol Denatured?

It all comes down to money and restricting access to alcohol for underage drinkers. Alcoholic beverages are heavily taxed. Ethanol is used for numerous important applications, so the only way to keep people from drinking this alcohol rather than the taxed alcohol is to denature it. That being said, denatured alcohol is never superior to normal ethanol, plus it’s more expensive to produce denatured alcohol than regular ethanol.

Chemicals Used as Denaturants

In some cases, denatured alcohol may contain less than 50% ethanol! Methanol (methyl alcohol) is the most common chemical used as a denaturant. Other common additives include isopropanol (isopropyl alcohol), acetone, methyl ethyl ketone, and methyl isobutyl ketone. Other denaturants include (but are not limited to) benzene, diethyl phthalate, and naphtha. Pyridine may be added to give denatured alcohol an unpleasant fishy odor. Denatonium (Bitrex or Aversion) may be added to denatured alcohol to make it taste bitter. Syrup of ipacac may be included to induce vomiting, should the product be ingested. With the exception of denatonium and syrup of ipacac, denaturants have properties similar to those of ethanol, so it’s difficult to separate them and purify the alcohol. Most denaturants are toxic.

Usually, the formulation of denatured alcohol is not known. However, specially denatured alcohol (SDA) is a combination of ethanol and a known denaturant. For example, SDA 40-B contains denatonium benzoate and tert-butyl alcohol. SDA 35 and SDA 35-A contain ethyl acetate. Specifically denatured alcohol is used in pharmaceuticals, solvents, and cosmetics, in cases where certain denaturants must be avoided.

Some countries specify the formula for denatured alcohol. For example, the European Union (February 2013) requires denatured alcohol consist of 3 liters isopropyl alcohol, 3 liters methyl ethyl ketone, and 1 gram denatonium benzoate per 100 liters of absolute ethanol. British regulations (2005) specify 90 parts ethanol, 9.5 parts wood naphtha, and 0.5 parts pyridine, resulting in a mixture that is dyed with methyl violet and further denatured with 3.75 liters petroleum oil per 1000 liters of alcohol mixture.

Uses of Denatured Alcohol

Generally, denaturants are chemically similar to ethanol, so the product can be used in fuels, some lab situations, and as a disinfectant. Denatured alcohol is found in hand sanitizer, rubbing alcohol, lotions, and cosmetics. However, denatured ethanol is unsuitable for precipitation of nucleic acids. Denatured ethanol containing methanol is unsuitable for use in any product used on the skin, as methanol is a toxic alcohol that is absorbed through skin.

Identifying Denatured Alcohol

Denatured alcohol is identified on the product label. Some countries require dyeing denatured alcohol, usually blue or purple using an aniline dye or methyl violet. This clearly identifies the product as unsafe to drink. However, the United States does not require coloring denatured alcohol. In the U.S., denatured alcohol is clear and impossible to visually distinguish from normal ethanol.

What Happens If You Drink Denatured Alcohol?

Do not drink denatured alcohol or methylated spirits. If methanol is the denaturing agent, possible risks include nervous system and other organ damage, increased cancer risk, and possibly death. Most other denaturants carry similar health risks. Also, denatured alcohol often contains dyes and perfumes not intended for human consumption. Use caution incorporating denatured alcohol into cosmetics and skincare products, as some denaturants are toxic if used on the skin.

It’s a common misconception that denatured alcohol may be purified by distillation to make it suitable for drinking. While an experienced chemist may be able to purify ethanol from denatured alcohol, the boiling points of denaturants tend to be too close to that of ethanol for the average person to separate the compounds.

References

  • 27 CFR 20. Regulations Relating to Denatured Alcohol in the United States.
  • Ali, Y.; Dolan, M.J.; Fendler, E.J.; Larson, E.J. (2001) Alcohols in Disinfection, Sterilization, and Preservation (5th ed.).
  • Kosaric, N.; Duvnjak, Z.; et al. (2011). “Ethanol.” Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH. Weinheim. doi:10.1002/14356007.a09_587.pub2

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