Methylated spirit

From Wikipedia, the free encyclopedia

Methylated spirit (or Meths, see also denatured alcohol or Rubbing 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 its name, but this is not always the case now. There are diverse industrial uses for ethanol, and therefore literally hundreds of recipes for denaturing ethanol. Typical additives are methanol, isopropanol, methyl ethyl ketone, methyl isobutyl ketone, denatonium, and even (uncommonly) aviation gasoline.

As used 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 methylated spirit 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 impossible because it forms an azeotropic mixture and will have the same boiling point. In many countries, it is also required to be dyed blue or purple with an aniline dye.

The tax-exempt status for denatured alcohol dates from the mid-19th century. For instance the United Kingdom introduced legislation in 1855 to permit ethanol containing 10% wood-naphtha to be exempt.

1 Formulations
2 Consumption and toxicity
3 Uses
4 Notes
5 External links

[edit] Formulations

The Irish specification is typical. The following are added to ethanol to make it into methylated spirit:

9.5 % wood naptha
0.5 % pyridine
0.025 ounce (0.709 grams) methyl violet dye per 100 gallons (378.5 litres) of ethanol
0.375 % petroleum oil

The naphtha and pyridine may be replaced with 10% methanol.

Industrial Methylated Spirit (IMS) UK formulation

This is a colourless liquid that is generally unavailable to the public. The production, purchase and use requires a licence or other authorisation. It consists of ethanol mixed with methanol to render it unfit for drinking. It is commonly used as a solvent in industry etc where the denaturants added to ordinary methylated spirit would render it unfit for the purpose. The ordinary coloured methylated spirit is freely available to the public and has a similar composition to the Irish formulation.

The regulations relating to denatured alcohol in the United States may be found at 27 CFR part 20.

[edit] Consumption and toxicity

Despite its poisonous nature, methylated spirit is sometimes drunk, alone, or mixed with other substances, by alcoholics who have become destitute. As such, there is an argument that the methanol or other poisonous component should be removed because it can cause death and blindness. It is also common to add a vomiting (emetic) agent, which serves a similar purpose without the fatal side-effects. Likewise, denatonium adds a bitter taste but will not kill.

It is not the methanol itself that is toxic, but 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 lungs and skin. (In a documented case, a shipworker 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."^[1])

[edit] Uses

A common use is as a fuel for marine and ultra-light camping (backpacking) stoves. Its main advantages are its low cost, its ability to be extinguished by water, the fact that it is not explosive, and its ability to be transported without special containers. However, safety concerns do arise from the near-colourless flame with which alcohol burns. In brightly-lit areas, an alcohol flame can be essentially invisible, creating a potential hazard wherein persons can be burned by contacting flames they cannot see.

One notable use is as a sanding aid, as the alcohol helps to more easily remove the excess sawdust that results from sanding wood, ^[2] because it does not open the wood grain the way that water would. Methylated spirits may also be used to kill mealybugs.^[3]

Methylated spirit 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.