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Properties of Hydrogen Cyanide

Hydrogen cyanide is a colorless or pale blue liquid when kept at room temperature. Use caution with hydrogen cyanide, because it is a very toxic and flammable substance. Hydrogen cyanide is also know as formonitrile, hydrocyanic acid and prussic acid.

  1. Flammability

    • Hydrogen cyanide is a very flammable liquid. It effectively mixes with air and can be a catalyst for explosive compounds. This substance is flammable from 5.6 percent to 40 percent concentration in the air. Hydrogen cyanide is flammable at temperatures above zero degrees Fahrenheit.

    Toxicity

    • Hydrogen cyanide can be fatal to humans when a person has an exposure of 50 parts per million or greater. Exposure limits for a human are 10 parts per million from the air; humans should not experience any significant medical side effects from this level of exposure. The skin absorbs hydrogen cyanide, and eye swelling can result from exposure. Between 10 to 50 parts per million, humans can experience side effects. Major exposure can result in brain injuries for the victim. Symptoms include personality change or memory loss. Hydrogen cyanide is poisonous because it is effects the enzymes in the lungs for respiration. Because of its lethality, its use extends into the gas chamber for prisoner executions.

    Odor

    • An unusual property of hydrogen cyanide is its odor. The liquid has a distinct bitter-almond odor. The odor is detectable at two to 10 parts per million. Some people cannot detect this odor. The ability to detect the almond odor is a genetic trait and between 20 percent to 40 percent of people do not possess this gene. As a result, the almond smell is not an adequate way to detect the presence of hydrogen cyanide.

    Chemistry of Hydrogen Cyanide

    • Hydrogen cyanide has a pH of 9.2. This means it is a weak acid. It boils at 78.8 degrees Fahrenheit. It is made from a hydrogen, a carbon, and a nitrogen atom. It ionizes in water, which means that it loses an electron and the hydrogen cyanide molecule has a positive charge.

    Origin

    • Hydrogen cyanide is found naturally in fruits with pits in them; 100 grams of apple seeds yield 10 milligrams of HCN, which is hydrogen cyanide. Some insects, like moths and millipedes, use this chemical as a natural defense mechanism.

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