What does chloral mean?
Chloral is a colourless, oily liquid organic compound with the formula CCl₃CHO — chemically, trichloroacetaldehyde — distinguished by a sharp, penetrating odour. It is manufactured by the reaction of chlorine with ethanol and serves mainly as an industrial intermediate: most notably in the production of DDT and other chemicals, and in making chloral hydrate, the compound's water-bound form that was introduced in the 1860s as one of the first reliable synthetic sleep-inducing drugs. Because of that history, "chloral" carries strong associations with Victorian medicine and, less flatteringly, with "knockout drops" — drugged drinks in detective fiction and real crime. Today the word belongs largely to chemistry and pharmacology; general readers encounter it mostly in discussions of forensic toxicology or the history of anaesthesia and sedation, where accuracy about its dual identity as industrial chemical and former sedative matters.
nounA colourless, oily liquid organic compound (CCl₃CHO) with a pungent odour, made by the action of chlorine on ethanol; in hydrated form it was formerly widely used as a sedative and hypnotic drug.
- The compound trichloroacetaldehyde (CCl₃CHO), a colourless pungent liquid used chiefly in chemical manufacture.
- By extension, especially historically, chloral hydrate when used as a sedative or hypnotic drug.
"The chemist prepared a solution of chloral for use as a laboratory reagent."
"Chloral is produced industrially by passing chlorine gas into absolute ethanol."
"In the late nineteenth century, physicians routinely prescribed chloral to patients suffering from insomnia."
Rarely pluralised; the plural appears only in technical writing referring to multiple samples or derivatives of the compound.
"The analysis detected trace amounts of several chlorals in the sample."
Chloral hydrate earned the nickname "knockout drops" — the notorious ingredient of the Mickey Finn slipped into victims' drinks in the age of Victorian crime fiction.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chloral
Chloral was named in the early nineteenth century by the German chemist Justus von Liebig, who first characterised the compound around 1832. The term combines "chlor-", from Greek "chlōros" meaning pale green or yellow-green (the same root that gives "chlorine", so called for its greenish-yellow gas), with the ending of "alcohol", reflecting Liebig's observation that the substance could be derived from ethanol by chlorination. It thus belongs to the same Greek-rooted family as "chloride", "chlorophyll", and "chlorate".
Related word forms
How chloral is actually used
Chloral is a technical term belonging chiefly to chemistry, pharmacology, and historical medical writing. In everyday contexts it appears almost exclusively within the fixed phrase "chloral hydrate." The bare word now reads as somewhat dated outside scientific literature, since the drug fell out of common therapeutic use in the twentieth century, though it survives in some hospital formularies as a sedative.
Easily confused with chloral
"Choral" is an adjective relating to a choir or chorus, while "chloral" is the name of a chemical compound; they are pronounced identically but entirely unrelated in meaning.
"Coral" is the hard calcareous substance formed by marine polyps (or its pinkish-orange colour), whereas "chloral" is an industrial chemical compound.