Cyanide salts are mainly used in electroplating, metallurgy, the production of organic chemicals (acrylonitrile, methyl methacrylate, adiponitrile), photographic development, the extraction of gold and silver from ores, tanning leather and in the making of plastics and fibres. They are also used to manufacture fumigation chemicals, insecticides and rodenticides.
Cyanide is a substance that is found in combination with other chemicals in the environment. The more common ones are Hydrogen cyanide (CASR# 74-90-8); sodium cyanide (CASR# 143-33-9); potassium cyanide (CASR# 151-50-8) and calcium cyanide (CASR# 592-01-8).
Substance name: Cyanide (inorganic) compounds
CASR number: 57-12-5
Molecular formula: CN-
Synonyms: Cyanides; Isocyanide; Cyanide ion; Cyanide anion; CYANIDE(1-) ION.
Hydrogen cyanide exists as colourless or pale blue liquid or gas with a bitter almond odour detectable at 1 to 5 ppm. Calcium cyanide, potassium cyanide, and sodium cyanide are all examples of simple cyanide salts. They are all white solids, are soluble in water, and smell like bitter almond.
Melting Point: Hydrogen cyanide: -13.4°C
Sodium cyanide: 563.7°C
Potassium cyanide: 634.5°C
Boiling Point: Hydrogen cyanide: 25.6°C
Sodium cyanide: 1496°C
Potassium cyanide: 1625°C
Density: Hydrogen cyanide: 0.699 kg/m3 (liquid)
Sodium cyanide: 1.6 kg/m3
Potassium cyanide: 1.52 kg/m3
Cyanides are a group of compounds based on a structure formed when carbon and nitrogen are combined. When cyanide combines with chemicals from the metals groups it forms simple salts. Calcium cyanide, potassium cyanide, and sodium cyanide all will liberate hydrogen cyanide (which is also soluble in water and smells like bitter almonds) in acidic water.
The National Pollutant Inventory (NPI) holds data for all sources of cyanide (inorganic) compounds emissions in Australia.
Very small amounts of cyanide in the form of vitamin B-12 (cyanocobalamin) are needed as part of a healthy diet. Cyanide is very toxic to humans and inhalation exposure can be rapidly fatal. Brief exposures to lower levels may result in shortness of breath, convulsions, and loss of consciousness. Exposure to high levels for short periods may result in irritation of the eyes, nose and throat, headache, pounding of the heart, shortness of breath, harm to the central nervous system, the respiratory system, and the cardiovascular system, and quickly lead to death. Long term exposure to low levels of cyanide may cause deafness, vision problems, and loss of muscle coordination. It may also effect the thyroid gland, which may cause cretinism (retarded physical and mental growth in children), or enlargement and over activity of the gland. These long-term effects are seen in people who eat large amounts of cassava, a cyanide containing vegetable.
Entering the body
Cyanide can enter the body when a person breathes air containing hydrogen cyanide or dust from cyanide compounds. This is most common for people who smoke or work in areas of higher exposure or near to facilities where cyanide compounds are used or produced. Cyanide may also enter the body when a person eats food or drinks water containing it. Cyanide released to the soil may pass into underground water systems. Cyanide is able to pass through the skin.
Workers in the industries that use or produce cyanide compounds are at risk of exposure. Consumers can be exposed to cyanide by exposure to air from production and processing facilities such silver and gold mining operations, chemical processing facilities, steel and iron industries, metallurgical industries, metal plating and finishing facilities and petroleum. Consumers may also be exposed to cyanide when using consumer products containing cyanide, such as pesticides. People who live in areas of high motor vehicle traffic, smoke, or breath smoke from burning trash are also at higher risk of exposure to cyanide.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standards for cyanide (inorganic) compounds through the workplace exposure standards for airborne contaminants. These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
- Maximum eight hour time weighted average (TWA): 10 parts per million (11 mg/m3)
- A peak limitation notice exists for this substance.
- Maximum eight hour time weighted average (TWA): 5 mg/m3
Drinking water guidelines
The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:
- Maximum of 0.08 milligrams per litre of water for health purposes
Cyanides have high acute (short-term) toxicity to aquatic life, birds, and animals. Insufficient data are available to evaluate the acute toxicity of cyanides on plants on land. Cyanides have high chronic (long-term) toxicity to aquatic life. Insufficient data are available to evaluate the chronic toxicity to plants, birds, or land animals. Cyanides are not expected to bioaccumulate.
Entering the environment
Cyanide compounds will be in the atmosphere as gases or small particles. They will then settle into the soil or water depending upon where the air currents carry them. Most cyanide compounds are water-soluble. These can contaminate ground water. They will evaporate out of the water. In the water cyanides are not persistent, they breakdown in a matter of days.
Where it ends up
Cyanide enters the environment from both natural and human processes. In air it is found mainly as the gas hydrogen cyanide, a small amount is present as fine dust particles. Most cyanide in surface water will form hydrogen cyanide and evaporate. It takes years for cyanide to breakdown from the air.
Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992):
Maximum of 0.005 mg/L (i.e. 0.00000 g/L)
Silver and gold mining operations (water or soil release), chemical processing facilities (water or air release), steel and iron industries (water or air release), metallurgical industries (water release), metal plating and finishing facilities (water release) and petroleum refineries are the largest point sources of cyanide(water or air release).
Diffuse sources, and industry sources included in diffuse emissions data
Use of pesticides (air, water, soil release) Burning of waste, tobacco products, certain plastics, wool, silk, and paper release cyanide to the air. Metal cleaning facilities tanneries, and photographic facilities may release cyanide to the air or water.
Some plants manufacture certain chemicals which when they decompose release cyanide. One of these chemicals (amygdalin) is found in the pits of apricots, peaches, cherries, apples, pears, and similar fruits and in sweet almonds. Enzymes in the human intestine are capable of releasing cyanide from this chemical, resulting in poisoning. Certain blue-green algae can produce cyanide as they metabolise nitrates.
Perhaps the largest source of mobile emissions of cyanide to the air is motor vehicle exhaust.
Consumer products containing cyanide products are pesticides, rodenticides, and other animal poisons, silver and metal polishes and photographic solutions.
Sources used in preparing this information
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- Agency for Toxic Substances and Disease Registry (1997), ToxFAQS Cyanide (accessed, May, 1999)
- Australian and New Zealand Environment and Conservation Council (ANZECC) (1992), Australian Water Quality Guidelines for Fresh and Marine Waters.
- CalEPA Air Resources Board Toxic Air Contaminant Summary Cyanide Compounds (accessed, May, 1999)
- ChemFinder WebServer Project (1995), Calcium Cyanide (accessed, May, 1999)
- ChemFinder WebServer Project (1995), Cyanide (accessed, May, 1999)
- ChemFinder WebServer Project (1995), Sodium Cyanide (accessed, May, 1999)
- Environmental Defense Fund (1998), Calcium Cyanide: The Chemical Scorecard: (accessed, May, 1999)
- Environmental Defense Fund (1998), Potassium Cyanide: The Chemical Scorecard: (accessed, May, 1999)
- Environmental Health Center, a division of the National Safety Council, Environment Writer – Chemical Backgrounders Cyanide Compounds (accessed, May, 1999)
- National Environment Protection Council (1998a), National Environment Protection Measure for the National Pollutant Inventory (accessed, May, 1999)
- New Jersey Department of Health, Right to Know Program (1986), TRIFacts, Sodium Cyanide (accessed, May, 1999)
- NTP Chemical Repository, Radian Corporation, Potassium Cyanide (AUGUST 29, 1991) (accessed, May, 1999)
- NTP Chemical Repository, Radian Corporation, Sodium Cyanide (AUGUST 29, 1991) (accessed, May, 1999)
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
- University of California, Davis; School of Veterinary Medicine, Vermont SIRI MSDS Archive Site: Sodium cyanide, technical (accessed, May, 1999)
- Worksafe Australia (1996), Hazardous Substance Hydrogen cyanide (salts) (accessed, May, 1999)
- Worksafe Australia (1996), Hazardous Substance Potassium cyanide (accessed, May, 1999)
- Worksafe Australia (1996), Hazardous Substance Sodium cyanide (accessed, May, 1999)
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed June 2021.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018