Ethanol

Ethyl Alcohol, chemical formula CH3CH2OH, sometimes simply known as Alcohol, is a drug used by both humans and San'Shyuum.

Overview
Ethanol is a flammable, colorless, mildly toxic chemical compound with a distinctive perfume-like odor, and is the alcohol found in alcoholic beverages. It is also known as EtOH, using the common organic chemistry notation of representing the ethyl group (C2H5) with Et. Ethanol is a straight-chain alcohol, and its molecular formula is C2H5OH. An alternative notation is CH3-CH2-OH, which indicates that the carbon of a methyl group (CH3-) is attached to the carbon of a methylene group (-CH2-), which is attached to the oxygen of a hydroxyl group (-OH). Its empirical formula is C2H6O, a formula that it shares with dimethyl ether.

Application
It has several medicinal uses, but is most well known for its intoxicating effects (it can be used as a depressant), and as such is used in a wide variety of alcoholic beverages, for example, the ancient human beverage beer is a standard drug carried aboard UNSC starships and facilities. It has a number of medical uses as well. While these were never specifically mentioned, historical earth armies used ethyl alcohol (and alcoholic beverages) as an antiseptic and general anaesthetic. This being so, it is very possible the UNSC continues this use when better alternatives are unavailable. The Covenant also possessed alcohol or a very similar intoxicant.

Ethanol is used in UNSC commercial vehicles as a biofuel, notably more advanced variants of the JOTUN series of agricultural drones. It is likely that this was corn ethanol, a derivative of corn used as an alternative fuel. Corporal Locklear was very aware of these facts, and managed to find the Medicinal Grade MED34-CH3CH2OH alcohol stores on the shortly before his death in the explosion of the Forerunner crystal.

Trivia

 * The Prophet of Regret, then the Vice Minister of Tranquility, once showed up drunk to a meeting with the Minister of Fortitude.
 * The San'Shyuum, and probably other species, drink a liquid to purge their bloodstream to make them sober when drunk.

List of appearances

 * Halo: First Strike
 * Halo: Ghosts of Onyx