Uses of Calcium Hydroxide
Calcium is a soft metal in the "alkaline earth" portion of the periodic table of the elements. It most commonly occurs in nature as carbonate. There are many forms calcium carbonate takes, including chalk, marble, calcite, aragonite, coral, seashells and pearls. It is from calcium carbonate that calcium oxide ("lime" or "quicklime") is made. In turn, calcium oxide is used to make calcium hydroxide. Calcium hydroxide has a number of important uses.
From Calcium Carbonate to Lime
Ordinary limestone or calcium carbonate (not dolomitic limestone, which also contains magnesium), has the chemical formula CaCO₃. By heating it in a kiln, carbon dioxide gas (CO₂) is given off, leaving behind the oxide, lime, as a white powder, CaO. Lime is used for various purposes, including the drawing of lines on sports fields and as a soil amendment in gardens. Marble may be used to prepare food-grade lime. In South America, lime is used in processing corn to produce a dehulled product that is easier to digest, and provides more nutrients to the eater.
From Lime to Calcium Hydroxide
Reacting lime and water, that is "hydrating" it or "slaking" it, forms the hydroxide. For this reason, calcium hydroxide is sometimes called slaked lime or hydrated lime. Its chemical formula is Ca(OH)₂. When lime is hydrated, it generates a great amount of heat and causes a boiling action, as if the material was alive, thus imparting the term quicklime (an old term for alive being "quick").
Nonfood and Medical Uses
Calcium hydroxide may be applied to some of the same uses as calcium oxide, including in steel manufacture, metallurgy, waste treatment, cement and mortar, and glass manufacture.
Calcium hydroxide may be used as a depilatory in the treatment of animal hides, since it dissolves hair. A formula of one pound to 10 gallons of water may be used to treat 20 pounds of hide. It is also used in some human hair-removal products as a substitute for shaving.
Food and Medical Uses
Calcium hydroxide is used in agriculture to adjust pH, since many soils are acid, whereas most crops grow better in near-neutral soils. It also provides calcium essential to plant cell walls, shoots and root-tips.
Calcium hydroxide is used in pickling (hence, yet another name, "pickling lime"). It is used in fungicide preparations and in insecticides.
Calcium hydroxide is used in endodontic (root-canal) dental applications.
Safety
The National Institute for Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards lists as Target Organs for calcium hydroxide the eyes, the skin and the respiratory system.
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