Chemical Lime: Properties, Production & Uses | [Your Brand/Website Name]

Chemical Lime

Lime (alkali)

Lime, a white powdery substance obtained from limestone, coral, oyster shells, and other substances containing calcium carbonate. Pure lime is calcium oxide. Most commercial lime, however, contains magnesium and other impurities.

Lime is produced by heating limestone or a similar substance in a kiln for several hours at a temperature of about 1800 F. (982 C.). The heat drives off carbon dioxide and converts the calcium carbonate into calcium oxide, or quicklime. When water is added to it, quicklime becomes slaked, or hydrated, lime. Hydraulic lime is made from limestone containing alumina, silica, and iron. Other variations or mixtures of lime include limewater (a suspension of slaked lime in water) and chlorinated lime.

Uses of Lime

Lime is one of the most important and widely produced industrial alkalies. Although the basic form, quicklime, is used to some extent, most lime used in industry is in the slaked form. Lime is used extensively in the manufacture of many substances, including steel, calcium carbide, glass, pulp, paper, and soap. In the leather industry, lime is used to loosen hair from hides in preparation for tanning. Lime is also used in the refining of sugar and petroleum. Farmers and gardeners add lime to the soil to reduce soil acidity.

Lime is sometimes added to public water supplies to reduce pipe corrosion and to soften water. Some sewage treatment plants use lime to control acidity and to remove phosphates from sewage. In air-pollution control, lime is used in devices called scrubbers to remove sulfur dioxide from furnace exhaust gases. The sulfur dioxide combines chemically with the lime to form a calcium-sulfate sludge that is removed periodically from the scrubber.

Lime has long been used in the construction industry to make mortar and plaster, serving as a binder in these substances. During the hardening process, the lime combines with carbon dioxide from the air to form rocklike calcium carbonate, while water is released by evaporation. Hydraulic lime is used to make a special kind of mortar that hardens under water.

Chemical formula for calcium oxide: CaO; for slaked lime: Ca(OH)2; for chlorinated lime: CaCl(ClO)* 4H2O.