Calcium hydroxide exists as a colorless crystal or a white powder. It has the chemical formula Ca(OH)2--the Ca signifies calcium and the OH signifies hydroxide. Other names for calcium hydroxide include slaked lime, pickling lime or hydrated lime. Lime is calcium oxide. When lime reacts with water, calcium hydroxide or slaked lime results. Calcium hydroxide will decompose in water only if heated. Otherwise, it remains in suspension. A suspension of fine calcium-hydroxide particles in water is called lime water, or milk of lime, and is used in chemical processing.
Calcium Hydroxide as a Flocculant
Calcium hydroxide is used mainly in its suspended form as lime. In this form, it can act as a flocculant. Flocculation is a process in which colloids, such as the calcium-hydroxide particles suspended in water, come out of suspension in the form of floc, or flakes. This is different from precipitation because the colloidal particles are suspended in the solution, not actually dissolved in it. Calcium-hydroxide suspensions neutralize excess acids found in sewage, and they regulate soil acidity. Calcium hydroxide also is used as a flocculant to neutralize excess acid formed during the industrial tanning process.
Calcium Hydroxide as an Ingredient in Industrial Compounds
Calcium hydroxide is an ingredient in whitewash, also known as calcimine, kalsomine or salsomine. It is a cheap paint made from calcium hydroxide and calcium carbonate. Calcium hydroxide also is an ingredient in mortar. Mortar originally was made of mud or clay, but today it is made of a mixture of sand; a binder such as cement, or lime, which is a mixture of calcium oxide and calcium hydroxide; and water. Calcium hydroxide also is used in plaster, such as lime plaster.
Calcium Hydroxide in Household Applications
Calcium hydroxide is an alkali, or a base, and can be used as a lye substitute. It is particularly useful in no-lye hair relaxer, making naturally curly hair less curly. It can be used as a chemical depilatory--a hair-removal chemical. It can even be used as a calcium supplement in baby formula.
Calcium Hydroxide as a Chemical Reagent
Calcium hydroxide is an additive in fungicides and in anti-mildew and anti-microbial formulas; it is designed to neutralize the acids in those solutions, forming a long-lasting fungicide. It can be added to aquariums to increase the bio-available calcium in solution for calcium-using organisms, such as algae and snails.
Calcium Hydroxide in Industrial Processes
Lime water, a saturated solution of calcium-hydroxide solution, is used in the neutralization of a variety of acids that form in an industrial process. In the petroleum-refining industry, it is used for the manufacture of additives to oils. It can be used in the manufacture of calcium stearate. In foods, it helps process water for alcoholic beverages and soft drinks. It is used in the separation of sugar from sugar cane, and in the processing of certain types of Norwegian fish. In the petrochemical industry, calcium hydroxide is used for manufacturing solid oils in the manufacture of brake pads and also is used in the manufacture of ebonite, a very hard rubber, and in the preparation of dry mixes for paint.
Food Uses of Calcium Hydroxide
In Native American and Latin American cooking, calcium hydroxide in the form of lime water is mixed with corn to make a food called nixtamal. Betel nut or coca leaves are chewed with calcium hydroxide to increase the bio-availability of the alkaloid stimulants they contain. Native Americans also chewed tobacco leaves with calcium hydroxide derived from burnt shells. Calcium hydroxide also can used as a preservative in vegetables.
Calcium Hydroxide in Dentistry
Calcium hydroxide is used in dentistry during root-canal procedures. It has anti-microbial and bone-regeneration stimulant properties.
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