Calcium carbide
Overview
 
Calcium carbide is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 of Ca
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...

C2
Carbide
In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides...

. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 (the rest is CaO, Ca3P2, CaS, Ca3N2, SiC, etc.). Because of presence of PH3, NH3, and H2S it has a distinctive smell which some find unpleasant.
Encyclopedia
Calcium carbide is a chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 of Ca
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...

C2
Carbide
In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides...

. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 (the rest is CaO, Ca3P2, CaS, Ca3N2, SiC, etc.). Because of presence of PH3, NH3, and H2S it has a distinctive smell which some find unpleasant. Its main use industrially is in the production of acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...

 and calcium cyanamide
Calcium cyanamide
Calcium cyanamide or CaCN2 is a calcium compound used as fertilizer, first synthesized in 1898 by Adolph Frank and Nikodem Caro . It is formed when calcium carbide reacts with nitrogen. It is commercially known as Nitrolime....

.

Production

Calcium carbide is produced industrially in an electric arc furnace
Electric arc furnace
An electric arc furnace is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from small units of approximately one ton capacity up to about 400 ton units used for secondary steelmaking...

 from a mixture of lime
Lime (mineral)
Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...

 and coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

 at approximately 2000 °C. This method has not changed since its invention in 1888:
CaO + 3 C → CaC2 + CO


The high temperature required for this reaction is not practically achievable by traditional combustion, so the reaction is performed in an electric arc furnace with graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

 electrodes. The carbide product produced generally contains around 80% calcium carbide by weight. The carbide is crushed to produce small lumps that can range a few mm up to 50 mm. The impurities are concentrated in the finer fractions. The CaC2 content of the product is assayed by measuring the amount of acetylene produced on hydrolysis. As an example, the British and German standards for the content of the coarser fractions are 295 L/kg and 300 L/kg respectively. Impurities present in the carbide include phosphide, which produces phosphine
Phosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...

 when hydrolysed.

This reaction was an important part of the industrial revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

 in chemistry, and was made possible in the USA as a product of massive amounts of cheap hydro-electric power liberated from Niagara Falls
Niagara Falls
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...

 before the turn of the 20th century.

The method for the production in an electric arc furnace
Electric arc furnace
An electric arc furnace is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from small units of approximately one ton capacity up to about 400 ton units used for secondary steelmaking...

 was discovered independently by T. L Willson
Thomas Willson
Thomas Leopold "Carbide" Willson was a Canadian inventor.He was born on a farm near Princeton, Ontario in 1860 and went to school in Hamilton, Ontario. By the age of 21, he had designed and patented the first electric arc lamps used in Hamilton...

 and H. Moissan
Henri Moissan
Ferdinand Frederick Henri Moissan was a French chemist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds.-Biography:...

 in 1888 and 1892.

Crystal structure

Pure calcium carbide is a colourless solid. The common crystalline form at room temperature is a distorted rock salt structure with the C22 units lying parallel.

Production of acetylene

The reaction of calcium carbide with water was discovered by Friedrich Wöhler
Friedrich Wöhler
Friedrich Wöhler was a German chemist, best known for his synthesis of urea, but also the first to isolate several chemical elements.-Biography:He was born in Eschersheim, which belonged to aau...

 in 1862.
CaC2 + 2 H2O → C2H2 + Ca(OH)2


This reaction is the basis of the industrial manufacture of acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...

, and is the major industrial use of calcium carbide. In China, acetylene derived from calcium carbide remains a raw material for the chemical industry
Chemical industry
The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials into more than 70,000 different products.-Products:...

, in particular for the production of polyvinyl chloride
Polyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

. Locally produced acetylene is more economical than using imported oil. Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons, with the capacity to produce 17 million tons. In the USA, Europe and Japan consumption is generally declining. Production levels in the USA in 1990s were 236,000 tons per year.

Production of calcium cyanamide

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide
Calcium cyanamide
Calcium cyanamide or CaCN2 is a calcium compound used as fertilizer, first synthesized in 1898 by Adolph Frank and Nikodem Caro . It is formed when calcium carbide reacts with nitrogen. It is commercially known as Nitrolime....

:
CaC2 + N2 → CaCN2 + C

Calcium cyanamide is used as fertilizer. It is hydrolysed to 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...

, H2NCN.

Steelmaking

Calcium carbide is used:
  • in the desulfurisation
    Desulfurisation
    Desulfurisation is a chemical reaction involving the removal of sulfur from a molecule .An important industrial desulfurisation processes is also the hydro-desulfurization of natural gas...

     of iron (pig iron, cast iron and steel)
  • as a fuel in steelmaking to extend the scrap ratio to liquid iron, depending on economics.
  • as a powerful deoxidizer
    Deoxidizer
    A deoxidizer is a chemical used in a reaction or process to remove oxygen. In comparison with antioxidants, deoxidizers are not used for stabilization during storage but for oxygen removal during manufacture...

     at ladle
    Ladle (metallurgy)
    In a foundry, a ladle is a vessel used to transport and pour out molten metals. Ladles range in size from small hand carried vessels that resemble a kitchen ladle and hold or to large steelmill ladles that hold up to...

     treatment facilities.

Carbide lamps

Calcium carbide is used in carbide lamp
Carbide lamp
Carbide lamps, properly known as acetylene gas lamps, are simple lamps that produce and burn acetylene which is created by the reaction of calcium carbide with water....

s, in which water drips on the carbide and the acetylene formed is ignited. These lamps were usable but dangerous in coal mines, where the presence of the flammable gas methane made them a serious hazard. The presence of flammable gases in coal mines led to the miner safety lamp
Safety lamp
A safety lamp is any of several types of lamp, which are designed to be safe to use in coal mines. These lamps are designed to operate in air that may contain coal dust, methane, or firedamp, all of which are potentially flammable or explosive...

. However, carbide lamps were used extensively in slate, copper and tin mines, but most have now been replaced by electric lamps. Carbide lamps are still used for mining in some less wealthy countries, such as in the silver mines near Potosi, Bolivia. Carbide lamps are also still used by some cavers exploring caves and other underground areas, though they are increasingly being replaced in this use by LED
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...

 lights. They were also used extensively as headlights in early automobiles, motorcycles and bicycles, although in this application they are also obsolete, having been replaced entirely by electric lamps.

Other uses

In the ripening of fruit, calcium carbide is used as source of acetylene gas, which is a ripening agent. (similar to ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

 which has the IUPAC name of ethene and the chemical formula of C2H4).

It is still used in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 for a traditional custom called Carbidschieten (Shooting Carbide). To create an explosion, carbide and water are put in a milk churn with a lid. Ignition is usually done with a torch. Some villages in the Netherlands fire multiple milk churns in a row as a New Year's Eve tradition. The tradition comes from an old pagan
Paganism
Paganism is a blanket term, typically used to refer to non-Abrahamic, indigenous polytheistic religious traditions....

 religious practice intended to chase off spirits.

It is used in toy cannons (see Big-Bang Cannon
Big-Bang Cannon
The Big-Bang Cannon is an early 20th century American toy that is still manufactured to this day. Numerous consumer fireworks injuries convinced a physics professor at Lehigh University to patent a "Gas Gun" in 1907. The manufacturing of Big-Bang Cannons started in 1912.The original name of the...

), as well as in bamboo cannon
Bamboo cannon
Meriam buluh or bamboo cannon is a type of home-made firecracker which is popular during the Hari Raya festive season in Malaysia, and during the New Year's day celebration in the Philippines...

s.

Together with calcium phosphide
Calcium phosphide
Calcium phosphide is a chemical is used in incendiary bombs. It has the appearance of red-brown crystalline powder or grey lumps, with melting point of 1600 °C. Its trade name is Photophor for the incendiary use or Polythanol for the use as rodenticide.It may be formed by reaction of the elements...

, calcium carbide is used in floating, self-igniting naval signal flares
Flare (pyrotechnic)
A flare, also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signalling, illumination, or defensive countermeasures in civilian and military applications...

 (see Holmes' Marine Life Protection Association
Holmes' Marine Life Protection Association
The Holmes' Marine Life Protection Association was a United Kingdom company set up in the 19th century to produce marine signal lights and foghorns. It was founded by Nathaniel John Holmes, a telegraph engineer from Middlesex; and it passed to his son Joseph R. Holmes...

).

External links

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