Denatured alcohol is ethanol which has been rendered toxic or otherwise undrinkable, and in some cases dyed. It is used for purposes such as fuel for spirit burners and camping stoves, and as a solvent. Traditionally, the main additive was 10% methanol, which gave rise to methylated spirits. There are diverse industrial uses for ethanol, and therefore literally hundreds of recipes for denaturing ethanol. Typical additives are methanol, isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, denatonium, and even (uncommonly) aviation gasoline.
In the phrase denatured alcohol, denatured means "a specific property of ethanol, its usefulness as a beverage, is removed". The ethanol molecule is not denatured in the sense that its chemical structure is altered.
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. Different additives are used to make it both unpalatable and poisonous in such a way that is hard to rectify through distillation or other simple processes. Methanol is commonly used for this in part because it has a boiling point close to that of ethanol, and separating it by distillation is difficult, but not impossible as methanol and ethanol form a zeotropic mixture (the opposite of an azeotropic mixture). In many countries, it is also required to be dyed blue or purple with an aniline dye.
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 wood naphtha or a substitute for wood naphtha 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.
One notable use is as a sanding aid, as the alcohol helps to more easily remove the excess dust that results from sanding wood, because it does not open the wood grain the way that water would. Methylated spirits may also be used to kill mealybugs.
Denatured alcohol is often also used for its solvent properties, for example to remove ink stains from upholstery or clothes.
Antiseptic mouthwash such as Listerine is denatured to avoid being taxed as an alcoholic beverage.
Ethanol can be used 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.
The toxicity of methanol is due to the accumulation of its metabolites — formaldehyde and formic acid. Because the metabolic pathways for ethanol and methanol share a common enzyme, alcohol dehydrogenase, ethanol can be used to treat methanol poisoning by blocking the enzyme until the body can excrete enough methanol through the kidneys, lungs and skin. In a documented case, a ship worker poisoned while cleaning out a methanol tank was successfully treated with administration of a good portion of the liquor in the ship's "medicine chest.
Alcohol and Tobacco Tax and Trade Bureau Issues Proposed Rule about Denatured Alcohol Formulas and Related Amendments
Jun 28, 2013; WASHINGTON, June 28 -- Alcohol and Tobacco Tax and Trade Bureau has issued a proposed rule called: Reclassification of Specially...