Chloral

Chloral, also known as trichloroacetaldehyde or trichloroethanal, is the organic compound with the formula Cl3CCHO. This aldehyde is a colourless oily liquid that is soluble in a wide range of solvents. It reacts with water to form chloral hydrate, a once widely used sedative and hypnotic substance.

Characters poisoned with chloral

 * Emily Brent - And Then There Were None (not fatally)
 * Quentin Duguesclin - The Clocks (not fatally)
 * John Savage - Why Didn't They Ask Evans? (initially suspected suicide, later revealed to be murder)
 * Ethel Rogers - And Then There Were None
 * Bella Tanios - Dumb Witness (suicide)
 * Rita Vandemeyer - The Secret Adversary
 * Gerald Wade - The Seven Dials Mystery