Methanol
Definition
Methyl alcohol, CH3OH. Boiling point 64.7°C. Found in wood spirit, windshield-washer fluid, and as a deliberate adulterant in illicit liquor. Toxic via its metabolite formic acid; lethal oral dose roughly 30 to 100 mL of pure methanol.
- Formula
- CH3OH
- Boiling point
- 64.7°C
- Sources
- Wood spirit, windshield-washer fluid, adulterated liquor
- Toxic metabolite
- Formic acid
- Lethal oral dose
- Roughly 30 to 100 mL of pure methanol
Common questions
Why is formic acid, not methanol itself, the main cause of toxicity?+
Methanol is metabolized by alcohol dehydrogenase into formaldehyde and then into formic acid, which accumulates and causes metabolic acidosis and damage to the optic nerve. This is also why ethanol or fomepizole can be given as antidotes, since they competitively block that metabolic pathway.
Why does illicit liquor adulteration with methanol cause mass poisoning outbreaks?+
Methanol is cheap and chemically similar enough to ethanol that it can be added to bulk up illicit spirits without an obvious taste difference, so a single contaminated batch distributed widely can poison many people who have no way of detecting the adulteration before drinking.
Related terms
- Chromotropic Acid Test
- Confirmatory colour test for formaldehyde (and hence indirectly for methanol). Chromotropic acid (4,5-dihydroxy-2,7-naphthalenedisulphonic acid) plus concentrated sulphuric acid plus formaldehyde gives an...
- Denatonium Benzoate
- Bittering agent (Bitrex), one of the bitterest known compounds, detectable by taste at the parts-per-billion level. Added at very low concentrations to...
- Denaturant
- A chemical added to industrial ethanol to make it unfit for human consumption (and therefore exempt from beverage-alcohol excise). Indian Standards list...
- Fomepizole
- 4-methylpyrazole. A competitive inhibitor of alcohol dehydrogenase used as the first-line antidote for methanol poisoning. Ethanol (oral or IV) is the older,...
- Formic Acid
- HCOOH. The toxic terminal metabolite of methanol, produced after alcohol dehydrogenase converts methanol to formaldehyde and aldehyde dehydrogenase oxidises formaldehyde to formate....
- Headspace GC-FID
- Gas chromatography with flame-ionisation detection run on the vapour above a sealed sample. The standard forensic method for methanol and ethanol in...
- Hooch
- Illicit, unregulated country liquor. Indian regional names include haatch, desi tharra, and santhi. Typically distilled from molasses, jaggery, or fermented fruit, with...