- Calcium hydroxide, with the chemical formula Ca(OH)₂, is an inorganic compound commonly known as slaked lime, hydrated lime, or pickling lime.
- It is a white, odorless, alkaline powder or crystal that is only slightly soluble in water, forming a solution known as limewater. Calcium hydroxide is produced by adding water to calcium oxide (quicklime) in a highly exothermic reaction:
- CaO + H₂O → Ca(OH)₂ + heat
- This reaction results in a soft, white powder with a high pH, making calcium hydroxide a strong base widely used in construction, industry, agriculture, and food processing.
- In the construction industry, calcium hydroxide is a critical component in the production of mortar, plaster, and whitewash. It plays a key role in masonry work due to its adhesive properties and resistance to weathering. Over time, when exposed to carbon dioxide in the air, it reacts to form calcium carbonate (CaCO₃), which hardens and strengthens building materials—a process known as carbonation.
- In agriculture, calcium hydroxide is used to adjust soil pH by neutralizing acidity, which improves nutrient availability and promotes healthier crop growth. It is also applied in animal husbandry to treat manure and reduce odors. Furthermore, it serves as a sanitizer and disinfectant on farms, helping to prevent the spread of pathogens.
- Calcium hydroxide has numerous environmental and industrial uses. It is employed in water and wastewater treatment to raise pH, remove impurities, and precipitate heavy metals. In flue gas treatment, it helps neutralize acidic emissions like sulfur dioxide, thereby reducing air pollution. In the chemical industry, it is used to manufacture products such as calcium salts, bleaching powder (calcium hypochlorite), and petrochemicals.
- In the food industry, calcium hydroxide is approved as a food additive and pH regulator. It is used in the preparation of traditional foods such as corn tortillas and hominy through a process called nixtamalization, which improves the nutritional profile and flavor of maize. It is also found in pickling solutions to maintain firmness in vegetables, hence the name “pickling lime.”
- In medicine and dentistry, calcium hydroxide is valued for its antibacterial and mineralizing properties. It is commonly used in endodontic treatments (root canals) to disinfect and promote healing within the tooth. Its high pH creates an environment unfavorable for bacterial survival, while encouraging the formation of secondary dentin.
- Despite its widespread usefulness, calcium hydroxide must be handled with care due to its caustic nature. Contact with skin or eyes can cause irritation or burns, and inhalation of dust may lead to respiratory discomfort. Appropriate personal protective equipment (PPE) is recommended when handling the substance in industrial or laboratory settings.
