Aquachloral

Aquachloral

Chloral hydrate is an organic compound with the formula C₂H₃Cl₃O₂. It is a colourless solid. It was once used as sedative and hypnotic drug. It remains a useful chemical reagent and precursor. It is derived from chloral (trichloroacetaldehyde) by the addition of one equivalent of water.

It was discovered through the chlorination of ethanol in 1832 by Justus von Liebig in Gießen. Its sedative properties were first published in 1869 and subsequently, because of its easy synthesis, its use was widespread. It was widely used recreationally and misprescribed in the late 19th century. Chloral hydrate is soluble in both water and alcohol, readily forming concentrated solutions. A solution of chloral hydrate in alcohol called "knockout drops" was used to prepare a Mickey Finn. More reputable uses of chloral hydrate include its use as a clearing agent for chitin and fibers and as a key ingredient in Hoyer's mounting medium, which is used to prepare permanent or semipermanent microscope slides of small organisms, histological sections, and chromosome squashes. Because of its status as a regulated substance, chloral hydrate can be difficult to obtain. To cope with procurement problems, Rutgers scientists have developed a substitute for chloral hydrate for use in microscopy, known as Visikol

It is, together with chloroform, a minor side-product of the chlorination of water when organic residues are present in the water, though concentrations rarely exceed 5 micrograms per litre (µg/L).

Chloral hydrate has not been approved by the FDA in the United States or the EMA in the European Union for any medical indication and is on the list of unapproved drugs that is still prescribed by clinicians. Usage of this drug as a sedative or hypnotic may be very dangerous given the lack of clinical trials.