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Cyanide Compounds
Description: Cyanides are a group of compounds based on a common structure formed when elemental nitrogen and carbon are combined. Cyanides are produced by certain bacteria, fungi, and algae, and may be found in food and plants. Cyanide itself is an ion, or combining form that carries a positive or negative charge. It is a powerful and rapid-acting poison. When cyanide combines with metals and organic compounds, it forms simple and complex salts and compounds. Sodium cyanide and potassium cyanide are examples of simple cyanide salts. Cyanide salts are mainly used in electroplating, metallurgy, and the production of organic chemicals; in photographic development; as anti-caking agents in road salts; in the extraction of gold and silver from ores; and in the making of plastics. Minor uses of cyanide salts include use as insecticides and rodenticides, as chelating agents, and in the manufacture of dyes and pigments. Cyanogen chloride is used as an insecticide. Of the cyanide compounds, sodium cyanide and potassium cyanide are the most likely to be found in the environment from industrial activities. Chemical properties: Calcium cyanide (CAS #592-01-8) is a white or colorless powder of crystals. It has a faint bitter almond odor. It is soluble in water with gradual liberation of hydrogen cyanide. It is a deadly poison when inhaled or digested. When heated to decomposition, it emits toxic fumes. Synonyms for calcium cyanide are alcyanide, cyanogas, calcid, calcyan, and cyanide of calcium. Copper cyanide (CAS #544-92-3) is a white solid that is insoluble in water. It is a poison that reacts violently with magnesium. When heated to decomposition, it emits very toxic fumes. Synonyms for copper cyanide are cupricin and cuprous cyanide. Cyanogen (CAS #460-19-5) is a colorless gas with an almond-like odor. It is soluble in water, ethanol, and ethyl ether. It is a poison that is very toxic to the eye. It is a very dangerous fire hazard via heat, flames, and oxidizers. When heated to decomposition or on contact with acid, acid fumes, water, or steam, it will react to produce highly toxic fumes. Synonyms for cyanogen are carbon nitride, dicyanogen, ethanedinitrile, and oxalonitrile. Cyanogen chloride (CAS #506-77-4) is a colorless gas with a highly irritating odor. It is soluble in water, ethanol, and ethyl ether. It is a poison that is very toxic to the eye. When heated to decomposition or on contact with water or steam, it will react to produce highly toxic and corrosive fumes. Synonyms for cyanogen chloride are chlorcyan, chlorine cyanide, and chlorocyanogen. Potassium cyanide (CAS #151-50-8) is a white solid or colorless water solution with a faint bitter almond odor. As a solution, it is slightly soluble in ethanol. It is a poison that reacts with acid or acid fumes to emit deadly hydrogen cyanide. When heated to decomposition, it emits very toxic fumes. As a solid, potassium cyanide is incompatible with nitrogen trichloride, perchloryl fluoride, sodium nitrite, acids, alkaloids, chloral hydrate, and iodine. A synonym for potassium cyanide is potassium salt of hydrocyanic acid. Potassium silver cyanide (CAS #506-61-6) is a poisonous, white solid made of crystals, which are light-sensitive. It is soluble in water and acids, and slightly soluble in ethanol. It emits very toxic fumes when heated to decomposition. Synonyms for potassium silver cyanide are potassium argentocyanide and potassium dicyanoargentate. Sodium cyanide (CAS #143-33-9) is a white crystalline solid that is odorless when dry, but emits a slight odor of hydrogen cyanide in damp air. It is slightly soluble in ethanol and formamide. It is very poisonous. It explodes if melted with nitrite or chlorate at about 450 degrees F. It produces a violent reaction with magnesium, nitrites, nitrates, and nitric acid. On contact with acid, acid fumes, water, or steam, it will produce toxic and flammable vapors. Synonyms for sodium cyanide are hydrocyanic acid, sodium salt; and cyanide of sodium. Health effects: Exposure to large amounts of all forms of cyanide for a short time can harm the brain, lungs, and heart, and cause coma and death. The health effects of all forms of cyanide are similar when large amounts are eaten, drunk, breathed, or touched. The first symptoms of cyanide poisoning are rapid, deep breathing and shortness of breath, followed by convulsions and loss of consciousness. In cases of acute cyanide poisoning, death is extremely rapid. Death may occur after ingestion of even small amounts of sodium cyanide or potassium cyanide and can occur within minutes or hours. Exposure to small amounts of cyanide compounds over long periods of time is reported to cause loss of appetite, headache, weakness, nausea, dizziness, and symptoms of irritation of the upper respiratory tract and eyes. Exposure to potassium cyanide or sodium cyanide can cause asphyxiation and death, weakness, headaches, confusion, nausea, vomiting, increased respiratory rate, and slow respiratory gasping. Potassium cyanide as a solid may cause poisoning when ingested, inhaled, or absorbed through the skin. Strong solutions are corrosive to skin, eyes, and mucous membranes. Exposure Values for: Economics: U.S. manufacturers of sodium cyanide are Dan River, Inc, Danville, VA; Dow Chemical USA, Freeport, TX; E I du Pont de Nemours & Co, Inc, Memphis, TN; and Sterling Chemicals, Inc, Texas City, TX. In 1990, the last year for which data are available, the U.S. companies that produced cyanide compounds were Matheson Gas Products, Inc., Gloucester, MA, cyanogen; DuPont, Memphis, TN, and W.R. Grace, Nashua, NH, potassium cyanide; Dow Chemicals, Freeport, TX, and DuPont, Memphis, TN, and Texas City, TX, sodium cyanide. Regulation: Cyanide compounds are regulated under the Emergency Planning and Community Right-to-Know Act; the Clean Air Act; the Comprehensive Environmental Response, Compensation and Liability Act; the National Primary Drinking Water Regulations under the Safe Drinking Water Act; and the Resource Conservation and Recovery Act. The Occupational Safety and Health Administration (OSHA) sets a permissible exposure limit, time-weighted average of 5 mg/m3 for cyanide salts. Releases of more than one pound of cyanide compounds into the air, water, and land must be reported annually and entered into the national Toxic Release Inventory. In 1993, 3,291,307 pounds of cyanide compounds were released by 175 facilities. Of those releases, 56,544 pounds were fugitive or nonpoint air emissions; 842,184 pounds were stack or point air emissions; 97,666 pounds were surface water discharges; 2,288,870 pounds were released by underground injection; and 6,043 pounds were released to land. National Overview of 1998 Toxics Release Inventory See EPA's Toxic Release Inventory. Notations: The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation "Ca." The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by "C" preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure. In addition, there are a number of substances from Table Z-2 (e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2 hours" means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday. Information Sources:
Originally published in Environment Writer by the National Safety Council. Reprinted with permission. Environment Writer Metcalf Institute for Marine and Environmental Reporting University of Rhode Island Graduate School of Oceanography Office of Marine Programs Narragansett, RI 02882 Tel: 401-874-6211; Fax: 401-874-6485 Disclaimer * Copyright 2002-2006 * All rights reserved. * University of Rhode Island |