Quicklime is a chemical compound which is widely used in the chemical industry. Let’s find out how it’s used.
Did You Know?
Quicklime was used in the infamous Holocaust. The Nazis would place a thick layer of quicklime on the floor of the cattle cars before loading the Jews. This would burn the skin of the victims on contact.
Quicklime, also known as burnt lime, is a chemical compound called Calcium oxide (CaO). It is a white or pale gray, odorless, crystalline solid or granular powder having a melting point of 2572 °C and a boiling point of 2850 °C. This compound is widely used in the industrial sector for a variety of purposes.
How is Quicklime Made?
Quicklime is made by means of a thermal decomposition reaction. A thermal decomposition reaction is the one in which a substance breaks down into simple substances, and a single reactant produces two or more products along with the emission of heat. Here, the reactant which is used is limestone (calcium carbonate), whereas the products that are formed are calcium oxide and carbon dioxide. The chemical equation for this reaction is given below:
CaCO3➜CaO + CO2
- CaCO3 stands for Calcium Carbonate
- CaO stands for Calcium Oxide
- CO2 stands for Carbon Dioxide
The aforementioned reaction is carried out in a special lime kiln, where limestone is heated to about 500°C – 600°C.
Calcium oxide can also be derived by heating calcium hydroxide (slaked lime) at high temperatures. The chemical equation is as given below:
Ca(OH)2➜ CaO + H2O
- Ca(OH)2 stands for Calcium Hydroxide
- CaO stands for Calcium Oxide
- H2O stands for Water
Uses Based on Chemical Properties
Property : Calcium oxide reacts with carbon dioxide to generate calcium carbonate.
Use: Making Mortar
☞ Calcium oxide is an essential compound to manufacture cement and mortar. It is mixed with water and sand to form a stiff paste called mortar. This mortar is used for cementing bricks/stones while constructing buildings. As the mortar solidifies, it becomes hard enough to secure the bricks/stones.
Calcium oxide, in its direct form, reacts slowly with carbon dioxide. Therefore, to accelerate the process, it is mixed with water to form carbon hydroxide, also known as slaked lime. The chemical equation is as follows:
CaO + H2O ➜Ca(OH)2
This calcium hydroxide quickly reacts with carbon dioxide to form a mortar. The chemical equation is given below:
Ca(OH)2 + CO2 ➜ CaCO3 + H2O
Property Calcium oxide forms solutions with silicates.
Use : Making of Glass
☞ Calcium oxide when heated with silica sand and sodium carbonate, forms a peculiar solution. When this solution cools down, it forms an amorphous, clear, colorless solid called glass.
Use: Manufacture of High-grade Steel and Iron
☞ Metals such as steel and iron are extracted from ores. These ores contain impurities such as silicates. To remove them, quicklime is added to the ores, and the mixture is melted at high temperatures. The silicates bond with the lime to form a liquid called slag, which is immiscible with the molten metal. This slag, which is full of impurities, can be easily drained out, leaving behind the purified metal.
Quicklime is used for the following purposes.
☞ It is used to make calcium supplements. Inside the human body, calcium oxide reacts with water to form calcium hydroxide which later breaks down into calcium and hydroxyl ions to be absorbed by the body.
☞ It is used to prepare whitewash, a form of white paint used for whitening the walls and other surfaces.
☞ It is used to line the inside walls of a furnace owing to its high melting point.
☞ It is used to prepare bleaching powder, calcium carbide, and calcium cyanamide.
☞ It is used to purify sugar and soften water.
☞ It is used for waste water treatment.
☞ It is used to manufacture medicines, paper, insecticides, and plant and animal food.
☞ It is used as a fertilizer for acidic soils.
☞ It is used to remove hair from animal hides.
Some Interesting Uses
☞ Quicklime has traditionally been used for the burial of dead bodies in open graves to eliminate the odor of decomposition that attracts flies and insects. In the past, it was used for burying victims of deadly diseases such as cholera and plague, so as to prevent them from spreading through air.
☞ Quicklime is incandescent (emits an intense glow on heating) when heated to 2400 °C. This bright white light emitted from quicklime is called limelight. Before the invention of the electric bulb, limelight was used to illuminate theatrical productions.
Since quicklime is alkaline in nature, any contact with the skin can cause undesirable reactions that range from mild irritation to full-scale burns. Therefore, care should be taken while handling this chemical.