| Chemical Properties | Calcium cyanamide is a blackish-gray, shiny crystalline material or powder.
|
| Physical properties | Pure product is a colorless, hexagonal crystal or white powder. Commercial grade material may be grayish-black powder or lump (the color is due to presence of calcium carbide and other impurities); density 2.29 g/cm3; melts around 1,340°C; sublimes around 1,150 to 1,200°C on rapid heating; reacts with water. |
| Uses | Manufacture of calcium cyanide and
dicyandiamide; formerly used as a defoliant and
herbicide |
| Uses | Calcium Cyanamide is used as a fertilizer, herbicide, insecticide, a steel-making additive and an ore processing material. It can also be used to make thiourea, guanidine and ferrocyanides. manufacture of calcium cyanide, melamine, dicyandiamide. |
| Uses | Calcium cyanamide has
its major use as a fertilizer. However, it has a number of other
uses, such as a herbicide and a defoliant for cotton plants. It is
finding increasing use as a chemical intermediate. For example,
it is being used to produce dicyandiamide, which in turn can be polymerized to form the widely used monomer,
melamine. The conversion to calcium cyanide and hence
into a variety of other uses is also important commercially. |
| Definition | ChEBI: The calcium salt of cyanamide, formed when calcium carbide reacts with nitrogen |
| Definition | calcium cyanamide: A colourlesssolid, CaCN2, which sublimes at1300°C. It is prepared by heating calciumdicarbide at 800°C in a streamof nitrogen:
CaC2(s) + N2(g) → CaCN2(s) + C(s)
The reaction has been used as amethod of fixing nitrogen in countriesin which cheap electricity isavailable to make the calcium dicarbide(the cyanamide process). Calciumcyanamide can be used as afertilizer because it reacts with waterto give ammonia and calcium carbonate:
CaCN2(s) + 3H2O(l) → CaCO3(s) +2NH3(g)
It is also used in the production ofmelamine, urea, and certain cyanidesalts. |
| Production Methods | Calcium cyanamide was first produced commercially around
1900 as a fertilizer. The process of making calcium cyanamide
involves three raw materials—coke, coal, and limestone—
plus nitrogen. The limestone (calcium carbonate) is
burned with coal to produce calcium oxide. The calcium
oxide is then allowed to react with amorphous carbon in the
furnace at 2000°C with the formation of calcium carbide
(CaC2). Finely powdered calcium carbide is heated to
1000°C in an electric furnace into which pure nitrogen
is passed. It is then removed and uncombined calcium
carbide removed by leaching. |
| Preparation | Calcium cyanamide is prepared from calcium carbide. The carbide powder is heated at about 1,000°C in an electric furnace into which nitrogen is passed for several hours. The product is cooled to ambient temperatures and any unreacted carbide is leached out cautiously with water.
CaC2 + N2 → CaCN2 + C (ΔHƒ°= –69.0 kcal/mol at 25°C)
|
| General Description | A colorless to gray, odorless solid. May cause illness from ingestion. May irritate the skin. If exposed to water or high temperatures, calcium cyanamide may generate toxic and flammable fumes. Used to make pesticides and in fertilizers. |
| Air & Water Reactions | Depending on the calcium carbide content, the cyanamide reacts with water (moisture from air or soil) to produce acetylene and hydrated calcium oxide or calcium hydroxide. Absorption of water during handling or storage of technical calcium cyanamide may cause explosion [Pieri, M. Chem. Abs. 46, 8335 1952]. |
| Reactivity Profile | When hydrated CALCIUM CARBIDE generates salts of calcium that are basic and are generally soluble in water. The resulting solutions contain moderate concentrations of hydroxide ions and have pH's greater than 7.0. They react as bases to neutralize acids. These neutralizations generate heat, but less or far less than is generated by neutralization of the bases in reactivity group 10 (Bases) and the neutralization of amines. They usually do not react as either oxidizing agents or reducing agents but such behavior is not impossible. |
| Hazard | Fire risk with moisture or combined with
calcium carbide. Skin, eye, and upper respiratory
tract irritant. Questionable carcinogen.
|
| Health Hazard | Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution. |
| Fire Hazard | Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard. |
| Flammability and Explosibility | Nonflammable |
| Agricultural Uses | Calcium cyanamide (CaCN2) is a dark colored,
granulated material containing around 21 % nitrogen. Its
dark color is due to the presence of calcium carbide.
Calcium cyanamide is produced by heating a mixture
of limestone with coal in a nitrogen atmosphere.
Generally, the process is carried out in three steps. In the
first step, calcium carbonate (limestone) is decomposed
at about 1100°C.
In the second step, calcium oxide (CaO) and coke (or
coal) are heated in an electric furnace to produce calcium
carbide.
The final step involves heating the powdered calcium
carbide at about 1100°C with pure nitrogen (produced by
liquefaction of air and fractional distillation) to produce
calcium cyanamide.
The fertilizer-grade calcium cyanamide contains 21 %
nitrogen, 11 % calcium, 11 % free carbon, 5% oil, 2 to
4% water and oxides of aluminum, iron and silicon. In
the presence of moisture and air, calcium
dicyandiamide (a poisonous compound) is formed. It
distinctly leaves alkalinity in the soil equivalent to 1.3 kg
calcium carbonate (CaCO3) per 0.45 kg of nitrogen
applied. At pH 7 or below, calcium dicyandiamide is
converted into urea and lime within one week of its being
in the soil.
When dry, calcium cyanamide is dusty but it is
generally used as granules. It is poisonous, irritating to
the skin and used as a pesticide, fertilizer and defoliant in
cotton. It is as good a fertilizer as sodium nitrate or
ammonium sulphate, but not as fast acting.
Calcium cyanamide is an excellent weed killer,
especially for tobacco plants, when applied 2 to 3 weeks
before sowing. It is also used for producing melamine,
urea and certain cyanide salts. |
| Safety Profile | Poison by ingestion,
inhalation, sh contact, intravenous, and
intraperitoneal routes. Moderately toxic to
humans by ingestion. Questionable
carcinogen with experimental tumorigenic
data. Mutation data reported. The fatal dose,
by ingestion, is probably around 20 to 30 g
for an adult. It does not have a cyanide
effect. Calcium cyanamide is not believed to
have a cumulative action. Flammable.
Reaction with water forms the explosive
acetylene gas. When heated to
decomposition it emits toxic fumes of NOx
and CN-. See also CALCIUM
COMPOUNDS, AMIDES, and
CYANIDE |
| Potential Exposure | Calcium cyanamide is used in agriculture as a fertilizer, herbicide; defoliant for cotton plants;
and pesticide. It is also used in the manufacture of dicyandiamide and calcium cyanide as a desulfurizer in the iron
and steel industry; and in steel hardening. |
| Carcinogenicity | Calcium cyanamide was weakly mutagenic
in Salmonella typhimurium strain TA1535 and
nonmutagenic in strain TA100. |
| Shipping | UN1403 Calcium cyanamide with .1% calcium
carbide, Hazard Class: 4.3; Labels: 4.3-Dangerous when
wet material |
| Incompatibilities | Commercial grades of calcium cyanamide may contain calcium carbide; contact with any form
of moisture solutions may cause decomposition, liberating
explosive acetylene gas and ammonia. Incompatible with
oxidizers (chlorates, nitrates, peroxides, permanganates,
perchlorates, chlorine, bromine, fluorine, etc.); contact may
cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. May
polymerize in water or alkaline solutions to dicyanamide.
Contact with all solvents tested also causes decomposition |
