- Calcium oxide, commonly known as quicklime or simply lime, is an inorganic compound with the chemical formula CaO.
- It appears as a white or grayish-white, odorless, caustic solid that is highly reactive, especially with water. Calcium oxide is produced through the process of calcination, in which calcium carbonate (CaCO₃)—typically in the form of limestone—is heated to high temperatures (above 825°C or 1517°F), driving off carbon dioxide and leaving behind calcium oxide.
- One of the most notable properties of calcium oxide is its highly exothermic reaction with water, producing calcium hydroxide (slaked lime) and releasing significant amounts of heat. This reaction is represented by the equation:
- CaO + H₂O → Ca(OH)₂ + heat
- Because of this intense heat release, calcium oxide is used in a variety of industrial and chemical processes, including applications where thermal energy is advantageous. For example, it is employed in the steel industry for removing impurities during smelting, and in environmental engineering for neutralizing acidic soils and water bodies. It is also widely used in the construction industry in the production of cement and mortar, where it plays a critical role in setting and hardening building materials.
- In agriculture, calcium oxide is used to treat acidic soils, a process known as liming, which improves soil structure, nutrient availability, and crop yield. It also acts as a disinfectant and drying agent in some farming practices. In waste treatment, quicklime is employed to stabilize sludge, reduce odors, and neutralize acids.
- Although calcium oxide has many beneficial uses, it is also a highly caustic and corrosive substance that must be handled with care. When it comes into contact with skin, eyes, or mucous membranes, it can cause severe irritation or chemical burns. Therefore, protective equipment such as gloves, goggles, and respiratory masks is essential when working with it.
- In some specialized medical and laboratory settings, calcium oxide may be used in chemical synthesis or to generate controlled heating. Historically, it was even used in limelight—a type of stage lighting in the 19th century, produced by directing a flame at a block of calcium oxide to emit a brilliant white light.
- While calcium oxide is not commonly used as a dietary calcium supplement due to its reactive and caustic nature, it may be indirectly involved in food processing (e.g., as a pH regulator) in its hydrated form, calcium hydroxide, which is milder and safer for controlled food-grade use.
