hydrocyanic acid

(hī'drōsīăn`ĭk): see hydrogen cyanidehydrogen cyanide,
HCN, colorless, volatile, and extremely poisonous chemical compound whose vapors have a bitter almond odor. It melts at −14&degC; and boils at 26&degC;. It is miscible in all proportions with water or ethanol and is soluble in ether.
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Hydrocyanic Acid

(also hydrogen cyanide, prussic acid, formonitrile), HCN, a colorless, mobile liquid with an odor of bitter almonds. Hydrocyanic acid was discovered in 1782 by K. W. Scheele. In 1811, J. Gay-Lussac obtained anhydrous hydrocyanic acid and determined its quantitative composition.

Hydrocyanic acid has a density of 0.688 g/cm³ at 20°C, a boiling point of 25.7°C, and a freezing point of – 14°C. It burns in air to yield H₂O, CO₂, and N₂; a mixture of hydrocyanic acid vapors and air explodes when ignited. Hydrocyanic acid, a very weak acid, decomposes upon storage, especially in the presence of impurities. Its salts are called cyanides, and its organic derivatives, nitriles. Hydrocyanic acid is formed upon hydrolysis of amygdalin, present in bitter almonds and apricots. An aqueous hydrocyanic acid solution can be obtained by the distillation of potassium ferrocyanide, K₄[Fe(CN)₆], with dilute sulfuric acid, H₂SO₄. The commercial method of hydrocyanic acid preparation is based on the interaction of a mixture of ammonia, methane, and air in the presence of a catalyst (Pt or an alloy of Pt and Rh):

2NH₃ + 2CH₄ + 3O₂ = 2HCN + 6H₂O

Hydrocyanic acid is highly toxic. It is used in railroad cars, granaries, and ships for disinsectization and deratization. Hydrocyanic acid serves as source material in the synthesis of certain high-molecular compounds.

S. A. POGODIN

Poisoning with hydrocyanic acid and its compounds can occur during the processing of ore (cyanidation) and the galvanization of metals, as well as during disinsectization and deratization. Entering the body through the respiratory passages or, more rarely, through the skin, hydrocyanic acid blocks the respiratory enzyme cytochrome oxidase and induces oxygen starvation in tissue. Symptoms of acute poisoning include irritation of the mucous membranes, asthenia, vertigo, nausea, and vomiting. These symptoms are followed by such respiratory disorders as infrequent, deep breathing, painful dyspnea, and, finally, slow breathing and respiratory arrest. Chronic poisoning is accompanied by headache, fatigue, and low arterial pressure. Changes are observed in electrocardiograms, and the blood is seen to-have a reduced sugar level and an increased content of, among other things, hemoglobin and lactic acid. The effect of potassium and sodium cyanides on the skin can be seen in cracking and eczema.

First aid treatment for acute poisoning involves, after conveying the victim into fresh air, the administration of amyl nitrite, carbogene, and oxygen vapors, the use of lobeline, cytiton, and cardiovascular agents, and the parenteral injection of solutions of sodium nitrite and sodium thiosulfate.

Preventive measures include the observation of safety rules, the use of protective garments for the skin, and periodic medical examinations.

REFERENCE

Navrotskii, V. K. Gigiena truda, 2nd ed. Moscow, 1974.

A. A. KASPAROV

hydrocyanic acid

[¦hī·drō·sī′an·ik ′as·əd] (inorganic chemistry) HCN_A highly toxic liquid that has the odor of bitter almonds and boils at 25.6°C; used to manufacture cyanide salts, acrylonitrile, and dyes, and as a fumigant in agriculture. Also known as formonitrile; hydrogen cyanide; prussic acid.

hydrocyanic acid

hydrogen

(H) [hi´dro-jen] a chemical element, atomic number 1, atomic weight 1.00797. (See Appendix 6.) It exists as the mass 1 isotope (protium, or light or ordinary hydrogen), mass 2 isotope (deuterium, heavy hydrogen), and mass 3 isotope (tritium).hydrogen cyanide an extremely poisonous colorless liquid or gas, HCN, a decomposition product of various naturally occurring glycosides and a common cause of cyanide poisoning. Inhalation of the gas can cause death within a minute. Called also hydrocyanic acid.heavy hydrogen deuterium.hydrogen ion concentration the degree of concentration of hydrogen ions (the acid element) in a solution. Its symbol is pH, and it expresses the degree to which a solution is acidic or alkaline. The pH range extends from 0 to 14, pH 7 being neutral, a pH of less than 7 indicating acidity, and one above 7 indicating alkalinity. See also acid-base balance.hydrogen peroxide H₂O₂, an antiseptic with a mildly antibacterial action. A 3 per cent solution foams on touching skin or mucous membrane and appears to have a mechanical cleansing action.hydrogen sulfide H₂S, a poisonous gas with an offensive smell, released from decaying organic material, natural gas, petroleum, and sulfur deposits, and sometimes used as a chemical reagent.

hy·dro·cy·an·ic ac·id (HCN),

(hī'drō-sī-an'ik as'id), HCN; A colorless, toxic liquid, with the odor of bitter almonds, present in bitter almonds (amygdalin), the stones of peaches, plums, and other drupes, and laurel leaves; inhalation of 300 ppm causes death. Synonym(s): hydrogen cyanide, prussic acid

hydrocyanic acid

hy·dro·cy·an·ic acid

hydrocyanic acid

hy′drocyan′ic ac′id

hydrocyanic acid

hydrocyanic acid

Hydrocyanic Acid

REFERENCE

hydrocyanic acid

hydrocyanic acid

hydrogen

hy·dro·cy·an·ic ac·id (HCN),

hydrocyanic acid

Synonyms for hydrocyanic acid

noun a solution of hydrogen cyanide in water

Synonyms

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