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I understand the need to denaturate alcohol, as to have a material that can be used for non-food products without the heavy alcohol beverage tax.

So, adding a foul tasting bitter substance like Denatonium seems like a great idea. It will also prevent children from accidentally chugging a bottle of the stuff.

But what I can't comprehend is: sometimes the alcohol is purposefully made poisonous. By adding methanol or other toxic substances. Can anyone tell me the logic behind this decision?

Is preventing tax avoidance so extremely important that they're willing to kill or blind anyone that might drink the illegal drink? Maybe they bought it without even knowing it was illegally made! Do they deserve to die? It just seems insane to me. Perhaps chemists in this site might have an explanation.

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    $\begingroup$ The amounts of typical denaturants are not usually large enough to kill you: they are mainly large enough to make the solution unpleasant to drink. Even methanol in small quantities is not that dangerous when consumed alongside ethanol (which is a treatment for methanol poisoning). $\endgroup$
    – matt_black
    Oct 6 at 16:40
  • $\begingroup$ I think this question itself is biased and due to that issue rightfully closed as opinion-based; I think -also in accordance with the currently accepted answer- it could be made less biased and the reopened. $\endgroup$ Oct 10 at 10:31
  • $\begingroup$ Is this some sort of an SJW joke? $\endgroup$ Oct 14 at 11:29
  • $\begingroup$ @KanghunKim I don't understand your comment. The question is about the purpose of poisoning alcohol rather than simply embittering it. Furthermore, if you are to downvote it would be good to write the reason in the comments $\endgroup$
    – Juan Perez
    Oct 14 at 14:28
  • $\begingroup$ "Is preventing tax avoidance so extremely important that they're willing to kill or blind anyone that might drink the illegal drink?".... sounds like an SJW tho 😅 $\endgroup$ Oct 16 at 12:42
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It seems there is not spread enough fact that ethanol is poisonous even before denaturation. "The dose makes the poison." - the old medieval wisdom.

Most of denatured ethanol is mixed rather with relatively harmless chemicals of repulsive bitter taste, like denatonium aka Bitrex. Often in mixture with other denaturants, as skilled drunkards are inventive in alcohol purification. :

Denatonium ... is the most bitter chemical compound known, with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharide.... Dilutions of as little as 10 ppm are unbearably bitter to most humans.... It is used as aversive agents (bitterants) to prevent inappropriate ingestion. Denatonium is used in denatured alcohol, antifreeze, preventive nail biting preparations, respirator mask fit-testing, animal repellents, liquid soaps, shampoos....... It is not known to pose any long-term health risks.

Methanol is added ( mixture known as methylated spirit ) usually to special lots for lab or technical usage where is implied the educated workers know what they are doing. The reason is methanol is one of the closest chemicals to ethanol, what is needed if usual additives would have disturbing effect due their physical or chemical properties. The methanol content is not very high, so toxicity of respective amount of methanol is comparable with toxicity of ethanol, for the given ratio.

The deadly cases in 2012 in Czech Republic were special, as evil motivated producers/sellers of cheap spirits mixed ethanol with methanol in ratio 1:1, not used in denaturation cases.

Pure ethanol is produced as well, but in limited scope, as danger of abuse is great.

There are various region specific denatured alcohol complex formulations as well, as example:

the formulation for completely denatured alcohol, according to 2005 British regulations was as follows: 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 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.

The European Union agreed in February 2013 to the mutual procedures for the complete denaturing of alcohol: Per hectolitre (100 L) of absolute ethanol: 3 litres of isopropyl alcohol, 3 litres of methyl ethyl ketone and 1 gram denatonium benzoate.

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  • $\begingroup$ So ethanol is not made poisonous to prevent consumption (which was what troubled me), but rather as a side effect of using methanol to keep it acceptable for laboratory use. $\endgroup$
    – Juan Perez
    Oct 6 at 19:39
  • $\begingroup$ Even water is considered poisonous in lab, so it does not matter, if ethanol contains methanol or not. $\endgroup$
    – Poutnik
    Oct 6 at 19:53
  • $\begingroup$ "Most of denatured ethanol is mixed rather with relatively harmless chemicals of repulsive bitter taste...Methanol is added ( mixture known as methylated spirit ) usually to special lots for lab or technical usage". Not sure if that's true. According to several sources, including sciencedirect.com/topics/agricultural-and-biological-sciences/…, the most common denaturant is methanol. $\endgroup$
    – theorist
    Oct 7 at 6:53
  • $\begingroup$ @theorist It may be region dependent. I have personally never encountered "methylated spirit" anywhere but in the lab. ( Czech Republic/Czechia ). Anytime I bought in my 56-year life denatured ethanol for outdoor ethanol burner, it reeked by pyridin-like smell. ( I did not taste it if it was bitter as hell due denatonium though ). I have no personal experience if publicly available methylated one uses other additional additives or not. $\endgroup$
    – Poutnik
    Oct 7 at 7:05
  • $\begingroup$ I would say pure ethanol is not produced in big amounts because it is prohibitively expensive, due to taxation. ;) $\endgroup$
    – Karl
    Oct 7 at 11:57

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