The poison acts by tying up all the body's hemoglobin, making it unavailable for transporting oxygen. Sublethal doses cause dizziness and headaches, similar to cases of carbon monoxide poisoning, since carbon monoxide also reacts with hemoglobin. Many natural substances contain hydrogen cyanide in a combined form, called amydalin. Peach pits and bitter almonds are examples. Combined cyanide is also responsible for the toxicity of the leaves of the yew tree, and of sorghum in the early stages of its growth.
Mature sorghum contains almost none of the relevant compound, and is used as an animal feed.
Today, cyanides are no longer manufactured from dried blood. Sodium cyanide is made in a series of reactions involving limestone, carbon, sodium carbonate and nitrogen from the air. Hydrogen cyanide is made on a large scale from methane, ammonia, and oxygen from the air. It is used in the production of nylon, among other uses, while sodium cyanide is used in the treatment of gold ores, and in electroplating, as discussed in last week's article.