| Description | Calcium cyanide is used mainly for the extraction or cyanidation of gold and silver ores. It is
also used in the production of prussiates or ferrocyanides, in the froth flotation of minerals,
in processes where gold complexes are adsorbed on carbon, in the manufacture of stainless
steel, as a fumigant and rodenticide, and as a cement stabiliser. The main users of cyanides
are the steel, electroplating, mining, and chemical industries. The principal cyanide compounds
used in industrial operations are potassium and sodium cyanide and calcium cyanide,
particularly in metal leaching operations. Cyanides have been well established in uses
as insecticides and fumigants; in the extraction of gold and silver ores; in metal cleaning; in the manufacture of synthetic fibres, various plastics, dyes, pigments, and nylon; and as
reagents in analytical chemistry. Calcium cyanide decomposes on heating above 350°C,
producing toxic fumes including nitrogen oxides and HCN. It reacts violently with water,
moist air, carbon dioxide, acids, and acid salts producing highly toxic and flammable HCN.
It reacts violently when heated with oxidising substances causing fire and explosion hazard. |
| Chemical Properties | Calcium cyanide is a white crystalline solid or
powder. Odor of hydrogen cyanide. |
| Uses | Calcium cyanide is used for the extraction of gold and silver from their ores, in the froth flotation of minerals, as a fumigant, and as a rodenticide. |
| Uses | Fumigant; rodenticide; in stainless-steel manufacture; in leaching ores of precious metals; stabilizer for cement. |
| Production Methods | Calcium cyanide is made commercially from lime, calcium
oxide, coke, and nitrogen. The reactions are carried out in an
electric furnace. The resulting melt is cooled rapidly to
prevent reversion to calcium cyanamide. The product is
marketed in the form of flakes, which are dark gray because
of the presence of carbon. The extraction or cyanidation of
precious-metal ores was the first and is still the largest use for
calcium cyanide. |
| General Description | White crystals or powder or gray-black powder (technical grade). Toxic by skin absorption through open wounds, by ingestion, and by inhalation. |
| Air & Water Reactions | Water soluble with evolution of some hydrogen cyanide, a flammable poison gas. Release of gas is much more rapid if acid is present. |
| Reactivity Profile | CALCIUM CYANIDE gives weakly acidic solutions. Contact with acids causes rapid evolution of hydrogen cyanide. Incompatible with isocyanates, nitrides, and peroxides. May react rapidly with oxidizing agents. |
| Hazard | Toxic by ingestion and skin absorption.
|
| Health Hazard | Calcium cyanide is a highly poisonous compound to humans, animals, and fish. The toxic routes are ingestion, skin contact, and inhalation of the dust. It forms HCN readily when it reacts with CO2 or water. This makes it highly hazardous, more so than the alkalimetal cyanides, although the LD50 value of Ca(CN)2 is greater than the sodium or potassium cyanides.
LD50 value, oral (rats): 39 mg/kg. |
| Health Hazard | Inhalation or ingestion causes headache, nausea, vomiting and weakness; high concentrations are rapidly fatal. |
| Fire Hazard | Special Hazards of Combustion Products: Decomposes in fire to give very toxic gases, including hydrogen cyanide. |
| Safety Profile | A deadly poison by
ingestion and probably other routes. When
heated to decomposition it emits toxic
fumes of NO, and CN-. See also
CALCIUM COMPOUNDS and
CYANIDE |
| Potential Exposure | Calcium cyanide is used as a fumigant; as a rodenticide; in leaching precious metal ores; in
the manufacture of stainless steel; and as a stabilizer forcement. Used as raw material for production of nitrogenous
compounds and in treatment of alcoholism |
| storage | Calcium cyanide is stored in tight containers free from moisture. Proper ventilation and protective equipment should be used while handling the solid or while preparing an aqueous solution. It is shipped in mild-steel or fiber drums. |
| Shipping | UN1575 Calcium cyanide, Hazard Class: 6.1;
Labels: 6.1-Poisonous materials |
| Incompatibilities | Contact with water, acids, acidic salts;
moist air, or carbon dioxide, forms highly toxic and flammable
hydrogen cyanide. Incompatible with fluorine, magnesium.
Reacts violently when heated with nitrites, nitrates, chlorates,
and perchlorates. Calcium cyanide decomposes in high heat
forming hydrogen cyanide and nitrous oxides fumes |
| Waste Disposal | Add cyanide waste to strong
alkaline sodium hypochlorite. Let stand 24 hours then flush
to sewage plant. |
