Cyanide is perhaps one of the most notorious poisons in the world. It comes in many different forms, and has been a popular method of dispatch throughout history. Cyanide is famously implicated in many real-life murders and suicides, and continues to be a popular trope in fictional writing due to its deadly reputation and universal infamy.
A Natural Killer
Cyanide is found in a number of plants and stone fruits, in the form of a compound called amygdalin. This compound is metabolised in the small intestine, where it reacts with hydrochloric acid found in the stomach to form hydrogen cyanide. Amygdalin is present in peach stones, apple seeds, and of course almonds. When it is said that cyanide tastes and smells of bitter almonds, it is actually the other way around; almonds taste of cyanide due to the high concentration of amygdalin.
However, this is not to suggest that any of these plants are inherently dangerous to consume. One would have to eat around 1000 apple seeds in a very small space of time in order to ingest a lethal dose of cyanide. Indeed, in the case of the muder of Sarah Hart in 1845, it was suggested that cyanide had been ingested accidentally through the victim’s consumption of apples. The jury, of course, saw through this rather feeble defence and the accused (John Tawell) was found guilty.
Dangerous Compounds
Cyanide is often found in the form of compound salts, normally potassium or sodium. Sucide capsules given to spies in the early twentieth century usually contained potassium cyanide, as it was quickly absorbed and thus ensured a speedy death. Potassium cyanide was also once a commonly used insecticide, where it was mixed with water to produce highly toxic hydrogen cyanide gas. This process was infamously perfected by the Nazis during WWII, when they used a cyanide based pesticide called Zyklon-B to murder around a million people in concentration camps throughout Europe.
Sniffing Out an Antidote
Cyanide is particularly deadly because it acts so quickly on the body. Once hydrogen cyanide is absorbed into the bloodstream, it rapidly attacks cells and prevents the body absorbing oxygen; the victim essentially suffocates. Most victims die within an hour of ingestion of a lethal dose, and sometimes within a few minutes. Symptoms include anxiety, confusion, nausea, and headaches, which are quickly followed by seizures and respiratory failure.
The first known antidote to cyanide was amyl nitrate, which is now recreationally known as ‘poppers’. When inhaled, the amyl nitrate provides a different substance for the hydrogen cyanide to bond with, allowing the body to process and excrete the cyanide. Many other modern antidotes work in a similar way, but often come with serious side effects and complications. Even today 95% of cyanide poisonings, both accidental and deliberate, are fatal.
Sources and Further Reading
Harkup, K., A is for Arsenic; The Poisons of Agatha Christie, (London, 2016)
https://wellcomecollection.org/works/q353b7hr/items?canvas=9&langCode=eng&sierraId=b22462533
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/cyanide