Chaux

Chaux, also known as quicklime or burnt lime, is a chemical compound with the formula CaO. It is a white, caustic, alkaline crystalline solid. It is produced by heating calcium carbonate (limestone) in a kiln to temperatures above 900 degrees Celsius, a process called calcination. This decomposes the calcium carbonate into calcium oxide and carbon dioxide gas. The reaction is: CaCO3 → CaO + CO2.

When chaux is mixed with water, it undergoes an exothermic reaction known as slaking, producing calcium hydroxide (Ca(OH)2), also called slaked lime or hydrated lime. The reaction is: CaO + H2O → Ca(OH)2. This slaked lime is less caustic than chaux.

Chaux has been used for thousands of years in a variety of applications. Historically, it was a key component in mortar for construction, and its use can be found in ancient Roman buildings and other historical structures. It reacts with carbon dioxide in the air over time to re-form calcium carbonate, thus hardening the mortar.

In modern times, chaux continues to be widely used. Its alkaline properties make it effective in water treatment and wastewater processing to neutralize acidity and precipitate impurities. In agriculture, it is used to adjust the pH of acidic soils, improving crop yields. The steel industry utilizes chaux as a flux to remove impurities during the smelting process. It is also an ingredient in the production of glass, paper, and certain plastics. Due to its caustic nature, proper handling procedures are necessary when working with chaux.