75-20-7 Usage
Description
Calcium carbide (CaC2) is a grayish-black hard solid with a garlic-like odor, produced from the chemical processing of limestone. It is an important chemical raw material, known for its ability to react with water to produce acetylene gas, calcium hydroxide, and release heat. Calcium carbide is used in various industries due to its unique properties and reactions.
Uses
1. Chemical manufacture:
Calcium carbide is used as a raw material for the production of acetylene gas, calcium cyanamide, and various acetylene derivatives.
It is also used in the production of calcium hydroxide.
2. Steel production:
In the steel industry, calcium carbide is used as a desulfurization agent for producing low-sulfur carbon steel.
It serves as a fuel in steelmaking and a powerful deoxidizer.
3. Mining, automobiles, and street lighting:
Calcium carbide is used in carbide lamps, providing a continuous acetylene flame for illumination in coal mines and other applications.
4. Fruit industry:
It is used for artificial ripening of fruit, utilizing the acetylene gas produced from its reaction with water.
5. Signal flares:
Calcium carbide is used in combination with calcium phosphide to create floating, self-igniting naval signal flares.
6. Cylinder gas:
It serves as a source of acetylene gas for metal fabrication and construction industries.
7. Experiment teaching:
Calcium carbide is used as a teaching reagent in experimental settings.
Reaction with water
Calcium carbide will immediately have reaction upon coming across with water, generating acetylene and calcium hydroxide, which is the approach of industrial preparation of acetylene (carbide method), the reaction equation is:
CaC2 + 2H2O = C2H2 + Ca (OH) 2.
Since the impurity of calcium carbide, the generated acetylene gas is usually mixed with a small amount of hydrogen sulfide, phosphine gas and other contaminants, so there is a bad smell. Calcium carbide is produced from the lime and coke in an electric furnace at a high temperature of 3000 ℃:
3C + CaO = CaC2 + CO.
Upon the laboratory preparation of acetylene, owing to the reaction between calcium carbide and water is very fierce, we can apply saturated brine to substitute water so that a pure and smooth airflow of acetylene can be obtained. Calcium carbide won’t have reaction with sodium chloride.
Production method
Electric furnace reduction method is the only method for industrial production of calcium carbide at present. Put calcium oxide and coke for reduction reaction at 2000~2200 ℃: CaO + 3C─ → CaC2 + CO-480644.64J, the resulting molten calcium carbide flow into the receiver tank from the bottom of the reactor, and we obtain the final product after cooling. Calcium carbide production belongs to high temperature operation with relative large amount dust being produced and consuming a large amount of electrical energy. In 1980s, the production of per ton of calcium carbide consumes industrial power of about 10~11GJ. In order to reduce the power consumption, people mostly apply large-scale and closed calcium carbide furnace to reduce heat loss and also do good to the recycling of carbon monoxide.
Preparation
Calcium carbide (CaC2) is manufactured by heating a lime and carbon mixture to 2000 to 2100°C (3632 to 3812°F) in an electric arc furnace. At those temperatures, the lime is reduced by carbon to calcium carbide and carbon monoxide (CO), according to the following reaction: CaO + 3C → CaC2 + CO
Lime for the reaction is usually made by calcining limestone in a kiln at the plant site. The sources of carbon for the reaction are petroleum coke, metallurgical coke, and anthracite coal. Because impurities in the furnace charge remain in the calcium carbide product, the lime should contain no more than 0.5 percent each of magnesium oxide, aluminum oxide, and iron oxide, and 0.004 percent phosphorus. Also, the coke charge should be low in ash and sulfur. Analyses indicate that 0.2 to 1.0 percent ash and 5 to 6 percent sulfur are typical in petroleum coke. About 991 kilograms (kg) (2,185 pounds [lb]) of lime, 683 kg (1,506 lb) of coke, and 17 to 20 kg (37 to 44 lb) of electrode paste are required to produce 1 megagram (Mg) (2,205 lb) of calcium carbide.
Reactions
Calcium carbide is grayish-black solid, reacts with water yielding acetylene gas and calcium hydroxide, formed at electric furnace temperature from calcium oxide and carbon.
Air & Water Reactions
Reacts rapidly with water to generate the flammable gas acetylene and the base calcium hydroxide. Enough heat may be generated to ignite the gas [Jones, G.W. BM Report Invest. 3755 1944].
Reactivity Profile
Calcium carbide is a reducing agent. May react vigorously with oxidizing materials. The powdered mixture of the acetylide and iron oxide and iron chloride burns violently upon ignition, producing molten iron. Calcium carbide incandesces with chlorine, bromine, or iodine at 245, 350, or 305°C., respectively, [Mellor, 1946, Vol. 5, 862]. The carbide burns incandescently when mixed and heated with lead difluoride, magnesium, hydrogen chloride, and tin (II) chloride, [Mellor, 1946, 1940, 1946, and 1941], respectively. Interaction of Calcium carbide with methanol to give calcium methoxide is vigorous , but subject to an induction period of variable length. Once reaction starts, evolution of acetylene gas is very rapid, unpublished observations [Bretherick 1995]. Mixing Calcium carbide with silver nitrate solutions forms silver acetylide, a highly sensitive explosive. Copper salt solutions would behave similarly, [Photogr. Sci. Eng., 1966, 10, 334]. The mixture of Calcium carbide and sodium peroxide is explosive, as is Calcium carbide and perchloryl fluoride as gases at 100-300°C.
Hazard
Forms flammable and explosive gas and
corrosive solid with moisture.
Health Hazard
It is a corrosive solid. Because it is highlywater-reactive, skin contact can cause burn.
Fire Hazard
Behavior in Fire: If wet by water, highly flammable acetylene gas is formed.
Safety Profile
Reaction on contact
with moisture forms explosive acetylene gas.
Flammable on contact with moisture, acid
or acid fumes; evolves heat or flammable
vapors. Moderate explosion hazard.
Incandescent reaction with Cl2 (245℃), Brz
(350℃), IS (305℃), HCl gas + heat, PbF2,
Mg + heat. Incompatible with Se, (KOH +
Ch), AgNO3, Na2O2, SnCl2, S, water.
Mixtures with iron(IⅡ) chloride, iron(IⅡ)
oxide, tin(Ⅱ) chloride are easily ignited and
burn fiercely. Vigorous reaction with
methanol after an induction period.
Addttion to silver nitrate solutions
precipitates the dangerously explosive silver
acetylide. Copper salt solutions behave
similarly. See also CALCIUM
HYDROXIDE and ACETYLENE.
Check Digit Verification of cas no
The CAS Registry Mumber 75-20-7 includes 5 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 2 digits, 7 and 5 respectively; the second part has 2 digits, 2 and 0 respectively.
Calculate Digit Verification of CAS Registry Number 75-20:
(4*7)+(3*5)+(2*2)+(1*0)=47
47 % 10 = 7
So 75-20-7 is a valid CAS Registry Number.
InChI:InChI=1/C2H2.Ca/c1-2;/h1-2H;/q;+2
75-20-7Relevant articles and documents
Ca2LiC3H: A new complex carbide hydride phase grown in metal flux
Lang, David A.,Zaikina, Julia V.,Lovingood, Derek D.,Gedris, Thomas E.,Latturner, Susan E.
, p. 17523 - 17530 (2010)
The reaction of carbon and CaH2 in a calcium/lithium flux mixture produces crystals of the new compound Ca2LiC3H. This phase forms with a new structure type in tetragonal space group P4/mbm (a = 6.8236(1) A, c = 3.7518(1) A, Z = 2, R1 = 0.0151). This is a stuffed variant of the Cs2(NH2)N3 structure, containing hydride anions in octahedral sites; the structure determination by single-crystal X-ray diffraction surprisingly allowed the hydrogen to be detected. The Ca2LiC3H structure also features the rarely seen C34- carbide anion; the protolysis reaction of this compound with ammonium chloride produces C 3H4. The electronic properties of Ca2LiC 3H were studied by quantum-chemical calculations including band structure and electron localization function (ELF) analysis; the phase is a charge-balanced semiconductor with a calculated band gap of 0.48 eV. This is in agreement with 7Li, 13C, and 1H MAS NMR data, which show resonances in the ionic region instead of the Knight shifted region. ELF analysis of the theoretical nonhydrided Ca2LiC3 structure confirms the ability of these calculations to properly locate hydrides and supports the structural model based on X-ray diffraction data.
On the coexistence of tetragonal and monoclinic CaC2: Structural and spectroscopic studies on alkaline earth metal acetylides, MC2 (M = Ca, Sr, Ba)
Reckeweg, Olaf,Baumann, Andreas,Mayer, Hermann A.,Glaser, Jochen,Meyer, H. -Jürgen
, p. 1686 - 1692 (2008/10/08)
The alkaline earth acetylides CaC2, SrC2 and BaC2 can be considered to occur in three polymorphic structures each. The monoclinic low-temperature form, the tetragonal form, and the cubic high-temperature form. No deviation from axial symmetry is obtained for the C22- ions in the tetragonal structure determinations, as confirmed by X-ray single-crystal structures and 13C MAS NMR studies. The CaC2 samples prepared by us were always a mixture of monoclinic and tetragonal phase. Their Raman spectra exhibited two distinct C2 streching vibrations. Problems arising from the coexistence of these two phases for the interpretation of 13C MAS NMR spectra are discussed.
BEHAVIOUR OF METAL CARBONATES IN SPECTROSCOPIC ARC, I. PRELIMINARIES. ROLE OF INSTABILITY OF CARBONATES
Szabo, Z. L.,Bertalan, E.,Tatar, E.
, p. 193 - 208 (2007/10/02)
Seven kinds of metal carbonates of different stability were studied in a.c. polarized arc, in Ar atmosphere, on mixtures with carbon powder of a molar fraction of 0.3 metal carbonate.The higher the thermal stability of the carbonate, the lower quantities of carbon oxides, measured by gas analytical methods were produced in the arc.The less stable carbonates suffer simple thermal decomposition, while in the case of Li2CO3 and BaCO3, carbon powder have a direct reducing effect.Under the conditions of the arc a substantial volume of CO was formed too, mainly according to the equation CO2 + C = 2 CO.Of the less stable carbonates, unstable metal oxides were formed, giving rise to further oxidation reactions.In the case of several carbonates, carbide formation could also be proved by gas analytical methods.Processes proceeding in the arc, their place, the depth of the reaction zone, etc., could be calculated and followed on the basis of data measured.Model substances for further investigations were chosen on the bases of these experiences.
