General Description
Grayish-black irregular lump solid. Used to make acetylene and in steel manufacture.
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 Once reaction starts, evolution of acetylene gas is very rapid, unpublished observations [Bretherick 1995].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.
Health Hazard
Eye and skin irritation
Fire Hazard
Behavior in Fire: If wet by water, highly flammable acetylene gas is formed.
Hazard
Forms flammable and explosive gas and
corrosive solid with moisture.
Chemical Properties
grey or black solid with a garlic-like odour
Physical properties
Grayish-black orthorhombic crystal; density 2.22 g/cm3; melts at 2,200°C; reacts with water.
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.
Potential Exposure
Those involved in the manufacture andhandling of carbide and the generation of acetylene.
First aid
If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24-48 h afterbreathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor orauthorized paramedic may consider administering a corticosteroid spray.
storage
Color Code—Red Stripe: Flammability Hazard:Do not store in the same area as other flammable materials.Color Code—Green: General storage may be used. Prior toworking with calcium carbide you should be trained on itsproper handling and storage. Store in tightly closed containers in a cool, well-ventilated area away from moisture andwithout sprinkler protection and avoid contact with incompatible materials. Use only nonsparking tools and equipment especially when opening and closing containers ofcalcium carbide. Metal containers involving the transfer ofthis chemical should be grounded and bonded. Use explosion-proof electrical equipment in the carbide-handlingarea. Sources of ignition, such as smoking and open flames,are prohibited where this chemical is used, handled, orstored in a manner that could create a potential fireor explosion hazard.
Shipping
Calcium carbide requires a “DANGEROUSWHEN WET” label. It falls in Hazard Class 4.3 andPacking Groups I or II.
Incompatibilities
Water contact or moist air forms calciumhydroxide and explosive acetylene gas with risk of fire andexplosion. Keep away from acids, oxidizers, hydrogenchloride, methanol, copper salt solutions, lead fluoride,magnesium, selenium, silver nitrate, iron trichloride, tindichloride, sodium peroxide, stannous chloride, sulfur.
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