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Calcium carbide

physical science Maturity 5-7 Next article →

Calcium carbide is a chemical compound with the formula CaC2. It is also known as calcium acetylide. This substance is highly important in modern industry. It serves as a primary source for creating acetylene gas. It also helps produce calcium cyanamide, which is used in farming.

Kristallstruktur Bariumperoxid
Kristallstruktur Bariumperoxid

Pure calcium carbide is a colorless solid. However, the technical-grade version used in factories is usually grey or brown. This industrial version is typically 80% to 85% pure calcium carbide. The remaining part contains substances like calcium oxide, calcium phosphide, and calcium sulfide. If this material touches even a tiny amount of moisture, it gives off a strong smell like garlic.

To understand its structure, we look at how its atoms are arranged. Calcium carbide is a calcium salt of acetylene. It consists of calcium cations and acetylide anions. At room temperature, it often forms a distorted rock-salt structure. This means the units lie parallel to one another. There are also three different polymorphs, or structural forms, that appear at room temperature. These include a tetragonal structure and two different monoclinic structures. This specific atomic arrangement allows it to react predictably with other elements.

Industrial production of calcium carbide follows a very specific process. It is made in an electric arc furnace. This furnace uses a mixture of lime and coke. The reaction requires extremely high temperatures to work. It is an endothermic reaction, meaning it must absorb heat to proceed. This process requires 427 kJ/mol of energy. Because traditional combustion cannot reach such high temperatures, manufacturers use graphite electrodes. These electrodes create an electric arc to provide the necessary heat. This heat also drives off carbon monoxide during the reaction. This manufacturing method has remained the same since its invention in 1892.

Once the carbide is produced, it undergoes further processing. The material is crushed into small lumps. These lumps can range from a few millimeters to 50 millimeters in size. The impurities in the mixture tend to concentrate in the finer, smaller pieces. Scientists check the quality of the carbide through an assay. They do this by measuring how much acetylene gas is produced during hydrolysis. Hydrolysis is the process of reacting the substance with water. For example, German standards require coarse fractions to produce 300 L/kg of acetylene at 101 kPa pressure.

Carbide lamp lit
Carbide lamp lit

The history of calcium carbide is tied to the Industrial Revolution. Two men discovered the electric arc furnace method in 1892. T. L. Willson and H. Moissan discovered it independently. In the United States, production grew because of cheap hydroelectric power from Niagara Falls. In 1899, Josef Kranz opened a massive factory in Jajce, Bosnia and Herzegovina. His company was called "Bosnische-Elektrizitäts AG." To power this factory, an 8 MW hydroelectric station was built on the Pliva river. This was the first power station of its kind in Southeast Europe.

Calcium carbide has many practical applications. Its most famous use is producing acetylene gas. Friedrich Wöhler discovered in 1862 that water reacts with calcium carbide to create acetylene and calcium hydroxide.

Carbide lamp lit
Carbide lamp lit

This gas is used in many ways. In China, it is a major raw material for making polyvinyl chloride. In other parts of the world, acetylene is made from methane instead. Calcium carbide is also used to make calcium cyanamide, or nitrolime. This is a vital fertilizer for crops. In steelmaking, it helps remove sulfur from iron and acts as a deoxidizer.

We can also see its history in older technologies like carbide lamps. These lamps work by dripping water onto the carbide to create burning acetylene gas.

Carbide lamp lit
Carbide lamp lit

They provided a brighter light than candles for miners. However, they were dangerous in coal mines because the gas could ignite methane. Today, most miners use electric or LED lights. You might still see carbide lamps used by cavers or in silver mines in Bolivia. Other uses include making toy cannons and even measuring moisture in soil. In a closed cylinder, the gas released from the reaction helps scientists calculate water content.

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File:Kristallstruktur Bariumperoxid.png
Kristallstruktur Bariumperoxid.png
File:Carbide lamp lit.jpg
Carbide lamp lit.jpg
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