What is Quicklime?

Quicklime is an alternate name for the chemical compound known as calcium oxide. This compound is represented by the chemical formula CaO and is also known as burnt lime. Under standard conditions for temperature and pressure, quicklime is known to exist as a crystalline solid that is white in colour. It is important to note that quicklime is known to be fairly caustic and alkaline under standard conditions. The term ‘lime’ is usually used to denote chemical compounds that contain the element calcium. Quicklime is known to be quite inexpensive and abundant. It can also be noted that quicklime (along with another one of its derivatives, calcium hydroxide) is a very important commodity chemical.

Preparation of Quicklime

Quicklime is a calcium oxide formed to release carbon dioxide by calcinating calcium carbonate (limestone). Quicklime is also referred to as handpicked lime, burnt lime, lump lime, calcining lime, and caustic lime. It is known to be a caustic material that is prepared at approximately 900 degrees Celsius by burning calcium carbonate limestone, carbon dioxide is forced off at this high temperature, and the limestone is converted to Quicklime.

It is a whitish, odourless alkaline substance with the chemical formula CaO. It can be noted that this compound does not dissolve well in water. As a lining material, it can be used. The main usage is in various industrial processes such as metal smelting, paper bleaching, sugar sulphur neutralisation, among many others.

Health Hazards Associated with Quicklime

Quicklime is known to be an irritant to the eyes and the skin. Therefore, it is advisable to use a full personnel protective equipment kit while handling this compound (including goggles, head hood, polyurethane and rubber gloves, cotton work suit, and leather boots). In case of any contact with the eyes, it is advisable to thoroughly wash the eyes with generous amounts of water and to immediately seek medical help. It is unadvisable to inhale quicklime dust since it can cause irritation to the respiratory tract.

Difference Between Quicklime and Hydrated Lime

The key differences between quicklime and hydrated lime lie in their reactivities and their chemical compositions. Hydrated lime and quicklime are both chemical compounds of calcium. Calcium is called calcium hydroxide when it is present in its hydrated form, and it is called calcium oxide (or quicklime) in its pure state. Calcium oxide is more reactive than hydrated lime and is also known to have a higher density.

When water is to powdered quicklime and the resulting mixture is subsequently placed it in a kiln or an oven, and then pulverised it with water, the product formed is hydrated lime. The resulting lime can also be referred to as calcium hydroxide. In a controlled environment, it is important to slake calcium oxide (quicklime) because it can produce relatively large amounts of heat. For water pH management, lime slurry mixes, lime slurry addition, soil regeneration and more, calcium hydroxide or hydrated lime is employed in an already neutralised state. This is done so that it doesn’t undergo oxidation and can be blended with water.

Properties of Quicklime

Quicklime is known to be an amorphous white solid with a high melting point of 2600 degrees celsius. It is a compound which is very stable and has the ability to withstand high temperatures. It forms slaked lime when it interacts with water. This method is often referred to as the slaking of lime. Quicklime is an oxide that, when bright into contact with an acid, forms salts.

Quicklime is known to crystallize in a cubic crystal lattice. The normal calcium oxide-associated molar entropy corresponds to 40 joules per mole kelvin. When heated to temperatures above 2400 degrees celsius, this compound is known to emit an intense glow.

Under standard conditions, the appearance of quicklime may range from white to pale yellow or brown. It is important to note that this compound does not have any characteristic odour. It can also be noted that quicklime is insoluble in methanol. It is also insoluble in octanol and diethyl ether.

Applications of Quicklime

Quicklime is used in a wide variety of applications, including the manufacture of iron and steel, the manufacture of paper and pulp, the treatment of water and flue gases and the mining industry.

In the basic oxygen steelmaking (BOS) process, quicklime is known to have very crucial applications. Quicklime and hydrated lime can increase the load-carrying ability of soils containing clay to a considerable extent. They accomplish this by participating in chemical reactions with finely divided alumina and silica in order to create calcium silicates and aluminates, which are known to have cementing properties. For use as an acidity regulator, a flour treatment agent, and as a leavener, this compound is classified as an FAO food additive.

A combination of calcium oxide and phenolphthalein is used in water detection pastes. The quicklime generally reacts with the water to form calcium hydroxide, should this paste come into contact with water in a fuel storage tank. Calcium hydroxide has a sufficiently high pH to turn a vibrant purplish-pink colour of the phenolphthalein, thereby signalling the presence of water.

To learn more about quicklime and other important calcium compounds such as calcium chloride, register with BYJU’S and download our app.

Frequently Asked Questions on Quicklime

In which state does quicklime exist under STP?

Under standard conditions for temperature and pressure, quicklime exists as a white to pale yellow powder. It can also exist as a pale brown coloured compound.

What is limelight?

When quicklime is heated to temperatures above 2400 degrees Celsius, it begins to emit a very intense glow. This type of illumination is generally referred to as limelight.

How can quicklime increase the load-carrying capacity of soils?

Quicklime, in combination with hydrated lime, can increase the load-carrying capabilities of clay-based soils by reacting with the alumina and the silica that is finely divided in the soil to produce silicates of aluminium and calcium.

What are the applications of quicklime in mining?

Quicklime is known to have applications in the production of compressed lime cartridges, which employ the exothermic properties held by quicklime in order to break certain types of rocks.

How can calcium oxide be prepared?

Calcium oxide, or quicklime, can be prepared via the thermal decomposition of seashells and limestone. This process is generally referred to as calcination.

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