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A bottle of Polish denatured alcohol.
Methylated spirit

Denatured alcohol (american english) or methylated spirit (british english) is ethanol that has additives to make it poisonous or unpalatable, and thus, undrinkable. In some cases it is also dyed.

Denatured alcohol is used as a solvent and as fuel for spirit burners and camping stoves. Because of the diversity of industrial uses for denatured alcohol, hundreds of additives and denaturing methods have been used. Traditionally, the main additive is 10% methanol, giving rise to the term methylated spirit. Other typical additives include isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and denatonium.[1]

In denaturing alcohol the ethanol molecule is not chemically altered, only the liquid's ingestability is affected.

Different additives are used to make it difficult to use distillation or other simple processes to reverse the denaturation. Methanol is commonly used because its boiling point is close to that of ethanol. In many countries, it is also required that denatured alcohol be dyed blue or purple with an aniline dye.

The tax-exempt status for denatured alcohol dates from the mid-19th century.

Contents

Purpose

Denatured alcohol is not, in itself, a preferred product — that is, it is not something which would be normally demanded if given the alternative of normal ethanol. Denatured alcohol and its manufacture are a public policy compromise. The supply and demand for denatured alcohol arises from the fact that normal alcohol (specifically ethanol, suitable for human consumption as a drink) is usually very expensive compared to similar chemicals, being highly taxed for revenue and public health policy purposes (see sin tax). As a result, if pure ethanol were made cheaply available as a fuel or solvent, people would drink it.

Denatured alcohol provides a solution to permit legitimate use and manufacture of ethanol, whereby cheap ethanol can be made available for non-consumption use without the risk of it being converted for consumption. The process creates a modified ethanol that is not suitable for drinking, but is otherwise similar to ethanol for most purposes. As a result there is no duty on denatured alcohol in most countries, making it considerably cheaper than pure ethanol. Consequently, its composition is tightly defined by government regulations which vary between countries.

In instances where absolutely pure ethanol is needed at a reasonable non-consumption-taxed price (for example, at chemical research laboratories), tight security procedures are required to eliminate the possibility of conversion for human consumption — specifically, tracking the purchase and distribution of the alcohol and ensuring compliance of workers who handle the pure ethanol.[citation needed]

Formulations

There are several grades of denatured alcohol, but the denaturants used are generally similar. The formulation for completely denatured alcohol, according to British regulations[2] is typical:

Completely denatured alcohol must be made in accordance with the following formulation: with every 90 parts by volume of alcohol mix 9.5 parts by volume of methanol or a substitute for methanol and 0.5 parts by volume of crude pyridine, and to the resulting mixture add mineral naphtha (petroleum oil) in the proportion of 3.75 litres to every 1000 litres of the mixture and synthetic organic dyestuff (methyl violet) in the proportion of 1.5 grams to every 1000 litres of the mixture.

Uses

Denatured alcohol has a variety of common uses:

  • As a fuel for marine and ultra-light camping (backpacking) stoves. It is inexpensive, may be extinguished with water, and can be transported without special containers. However, safety concerns do arise from the near-colourless flame with which alcohol burns. A jellied and dyed form is used in the Sterno brand fuel "Canned Heat", and is meant to be ignited and used in the container.
  • As a sanding aid, as the alcohol helps to more easily remove excess dust because it does not open the wood grain the way that water does.[3]
  • As a mealybug exterminator.[4]
  • As a cleaning aid in removing ink stains from upholstery or clothes
  • As a solvent in shellac and shellac-based products.
  • As an excipient in a number of pharmaceutical products for oral and topical use.[5]
  • As a less expensive alternative to pure ethanol in preserving biological specimens.
  • As a less toxic alternative to methanol in the production of biodiesel fuel. Biodiesel produced using ethanol is properly called fatty acid ethyl ester, whereas biodiesel from methanol is properly referred to as fatty acid methyl ester.[6]
  • As a germicide in the removal of fungus from skin and coldsore treatment.
  • For maintenance of wicks in kerosene heaters and lamps to remove water contaminents and restore the capillary action of the wick. As a wick cleaner and a kerosene additive, adding approx. 1 teaspoon denatured alcohol per gallon of kerosene. [7]

In the United States, small amounts of denatured alcohol are used in many consumer products such as toothpaste where they are labeled as "SD alcohol XX", where SD stands for "specially denatured" and XX is the formula used in the denaturing process that specifies the denaturants. These formulas for denatured alcohol are found in 27 CFR part 21 of the Code of Federal Regulations.[8] Some of these formulas, such as SD alcohol 38-B,[9] are designed to be unpalatable but otherwise non-poisonous; they are used in applications like mouthwashes where some amount of incidental ingestion is expected. (The specific denaturants in formulas 37 and 38-B closely resemble the active ingredients in alcohol-based mouthwashes like Listerine.[10])

Consumption and toxicity

Despite its poisonous nature, denatured alcohol is sometimes consumed as a surrogate alcohol, which can result in blindness or death if denatured alcohol contains methanol. To help prevent this, denatonium is often added to give the substance an extremely bitter flavor. Substances such as pyridine help to give the mixture an unpleasant odor, and emetic (vomiting) agents such as syrup of ipecac may also be included. In Poland and other European countries denatured alcohol contains only substances having bitter flavor (like acetylsalicylic acid) and odour, and does not contain methanol or any substance of severe toxicity.

Between 1926 and 1933, the United States federal government denaturing program, by some estimates, had killed at least 10,000 people.[11]

See also

References

  1. ^ "Ethanol Denaturants". The Online Distillery Network. 22 November 1993. http://www.distill.com/specs/EU2.html. 
  2. ^ "The Denatured Alcohol Regulations 2005". Office of Public Sector Information. 2005. http://www.opsi.gov.uk/si/si2005/20051524.htm. 
  3. ^ "Denatured Alcohol as a Sanding Aid". Woodzone.com. Unknown year. http://www.woodzone.com/tips/denatured.htm. Retrieved 2006-04-14. 
  4. ^ "Mealy Bug Treatment and Description". Succulents.co.za. http://www.succulents.co.za/succulent-plant-pests/mealy-bug.php. Retrieved 2007-09-30. 
  5. ^ http://www.accessdata.fda.gov/scripts/cder/iig/index.cfm FDA approved excipient database (search for "alcohol, denatured")
  6. ^ "Transesterification Process to Manufacture Ethyl Ester of Rape Oil" (PDF). University of Idaho. http://journeytoforever.org/biofuel_library/EthylEsterofRapeOil.pdf. Retrieved 2008-04-01. 
  7. ^ [1]
  8. ^ CFR Title 27 volume 1
  9. ^ 27 C.F.R. 21.65
  10. ^ SD alcohol 37 contains thymol, menthol, and eucalyptol, three of the four active ingredients in Advanced Listerine with Tartar Protection Antiseptic according to its Drug Facts label. SD alcohol 38-B allows a wide range of non-poisonous denaturants alone or in combination, including all four of Listerine's active ingredients.
  11. ^ Deborah Blum (February 19, 2010). "The Chemist's War". Slate magazine. http://www.slate.com/id/2245188/. Retrieved 2010-02-23. "Frustrated that people continued to consume so much alcohol even after it was banned, federal officials had decided to try a different kind of enforcement. They ordered the poisoning of industrial alcohols manufactured in the United States, products regularly stolen by bootleggers and resold as drinkable spirits. The idea was to scare people into giving up illicit drinking. Instead, by the time Prohibition ended in 1933, the federal poisoning program, by some estimates, had killed at least 10,000 people." 

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