Cyanide

Cyanide is a chemical compound containing a cyano group (a carbon atom triple-bonded to a nitrogen atom). Cyanide compounds are highly toxic. They bring about asphixiation and kill almost instantly. When cyanide has been used, there is usually the characteristic smell of bitter almonds.

Cyanide compounds

 * Hydrogen cyanide, also called prussic acid. A liquid. The fumes of this could be inhaled.
 * Potassium cyanide. A white cystaliine substance which could be added to drinks.

Characters poisoned with cyanide

 * Dr Ames - The Adventure of the Egyptian Tomb (suicide). He had tried to poison Poirot with a tisane spiked with cyanide but was exposed. He grabbed the drink and swallowed it himself.
 * George Barton - Sparkling Cyanide
 * Rosemary Barton - Sparkling Cyanide
 * Derek Bradley - Curtain
 * Emily Brent - And Then There Were None
 * Sir Arthur Carmichael - The Strange Case of Sir Arthur Carmichael
 * Adele Fortescue - A Pocket Full of Rye
 * Michael Garfield? - Hallowe'en Party (suicide)
 * Claudia Hardcastle - Endless Night
 * Samuel Long - The Gate of Baghdad (suicide)
 * Anthony Marston - And Then There Were None
 * Mayerling - The Big Four. He had been gagged and forced to inhale Prussic acid.
 * Mary Pritchard - The Blue Geranium
 * Ellie Rogers - Endless Night
 * Iris Russell - Yellow Iris
 * Mona Symmington - The Moving Finger
 * Ella Zielinsky - The Mirror Crack'd from Side to Side