quicklime

Quicklime is calcium oxide, CaO, a white or grayish alkaline solid produced by calcining limestone (calcium carbonate) at high temperatures. The calcination reaction releases carbon dioxide: CaCO3 → CaO + CO2. In air, quicklime reacts with moisture and carbon dioxide, forming calcium hydroxide or calcium carbonate on exposure.

Industrial production occurs in lime kilns or rotary kilns, where limestone is heated to about 900–1000°C. After cooling and screening, quicklime may be used as is or reacted with water to form hydrated lime (calcium hydroxide, Ca(OH)2), a process known as slaking.

Uses of quicklime are diverse. In construction, it is used for lime mortar, plasters, and soil stabilization, and it contributes to cement manufacture. It serves as a flux in steelmaking and as a chemical reagent in water and wastewater treatment to adjust pH and neutralize acidity. In sugar processing, lime is used to purify and clarify solutions. Quicklime is also employed in environmental remediation to raise soil pH and to treat acidic stormwater or landfills.

Safety and handling are important due to its caustic and highly reactive nature. Quicklime reacts vigorously with water, releasing heat and potentially causing burns. It should be stored in dry, tightly closed containers away from moisture and acids, and handled with appropriate protective equipment to prevent inhalation of dust and contact with skin or eyes.

Storage notes include avoiding exposure to moisture and carbon dioxide, which can gradually convert CaO to calcium hydroxide or calcium carbonate. Proper containment and ventilation minimize nuisance dust and reaction hazards.