Calcium cyanamide
Encyclopedia
Calcium cyanamide or CaCN2 is a calcium
compound used as fertilizer
, first synthesized in 1898 by Adolph Frank
and Nikodem Caro
(Frank-Caro process). It is formed when calcium carbide
reacts with nitrogen
. It is commercially known as Nitrolime.
The reaction takes place in large steel chambers. An electric carbon element heats the reactants to red heat. Nitrogen is pressurised at 2 atmospheres.
It crystallizes in hexagonal crystal system
with space group
R3m and lattice constant
s a = 3.67, c = 14.85 (.10−1 nm).
. 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.
. In contact with water it decomposes and liberates ammonia
:
It was used to produce sodium cyanide
by fusing with sodium carbonate
, which was used in cyanide process in gold mining:
It can also be used in the preparation of calcium cyanide
and melamine
.
Through hydrolysis, calcium cyanamide produces cyanamide
.
The conversion is conducted on slurries, consequently most commercial cyanamide is sold as an aqueous solution.
Thiourea
can be produced by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide.
Calcium cyanamide is also used as a wire-fed alloy in steelmaking, in order to introduce nitrogen into the steel.
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
compound used as fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
, first synthesized in 1898 by Adolph Frank
Adolph Frank
Adolph Frank was a German chemist, engineer, and businessman. He is best known for having discovered uses of potash and creating the industry....
and Nikodem Caro
Nikodem Caro
Nikodem Caro was an industrial chemist and entrepreneur. Caro was born in Łódź, and studied chemistry in Berlin at the Royal Technical College of Charlottenburg and got his doctorate from Rostock University...
(Frank-Caro process). It is formed when calcium carbide
Calcium carbide
thumb|right|Calcium carbide.Calcium carbide is a chemical compound with the chemical formula of CaC2. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 . Because of presence of PH3, NH3, and H2S it has a...
reacts with nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
. It is commercially known as Nitrolime.
- CaC2 + N2 → CaCN2 + C
The reaction takes place in large steel chambers. An electric carbon element heats the reactants to red heat. Nitrogen is pressurised at 2 atmospheres.
It crystallizes in hexagonal crystal system
Hexagonal crystal system
In crystallography, the hexagonal crystal system is one of the 7 crystal systems, the hexagonal lattice system is one of the 7 lattice systems, and the hexagonal crystal family is one of the 6 crystal families...
with space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
R3m and lattice constant
Lattice constant
The lattice constant [or lattice parameter] refers to the constant distance between unit cells in a crystal lattice. Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c. However, in the special case of cubic crystal structures, all of the constants are...
s a = 3.67, c = 14.85 (.10−1 nm).
Preparation
Calcium cyanamide is prepared from calcium carbideCalcium carbide
thumb|right|Calcium carbide.Calcium carbide is a chemical compound with the chemical formula of CaC2. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 . Because of presence of PH3, NH3, and H2S it has a...
. The carbide powder is heated at about 1,000°C in an electric furnace into which nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
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)
Uses
The main use of calcium cyanamide is in agriculture as a fertilizerFertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
. In contact with water it decomposes and liberates ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
:
- CaCN2 + 3 H2O → 2 NH3 + CaCO3
It was used to produce sodium cyanide
Sodium cyanide
Sodium cyanide is an inorganic compound with the formula NaCN. This highly toxic colorless salt is used mainly in gold mining but has other niche applications...
by fusing with sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
, which was used in cyanide process in gold mining:
- CaCN2 + Na2CO3 → 2 NaCN + CaO + O2
It can also be used in the preparation of calcium cyanide
Calcium cyanide
Calcium cyanide is an inorganic compound with the formula Ca2. It is the calcium salt of hydrogen cyanide. At normal conditions, it appears as colorless crystals or white powder with characteristic odor of bitter almonds . Like other similar cyanides it is very toxic...
and melamine
Melamine
Melamine is an organic base and a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 66% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses....
.
Through hydrolysis, calcium cyanamide produces cyanamide
Cyanamide
Cyanamide is an organic compound with the formula CN2H2. This white solid is widely used in agriculture and the production of pharmaceuticals and other organic compounds. It is also used as an alcohol deterrent drug in Canada, Europe and Japan. The molecule features a nitrile group attached to an...
.
- CaCN2 + H2O + CO2 → CaCO3 + H2NCN
The conversion is conducted on slurries, consequently most commercial cyanamide is sold as an aqueous solution.
Thiourea
Thiourea
Thiourea is an organosulfur compound of with the formula SC2 . It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad...
can be produced by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide.
Calcium cyanamide is also used as a wire-fed alloy in steelmaking, in order to introduce nitrogen into the steel.