Calcium

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Article updated on 03/03/20 by Priyom Bose

Calcium (Ca) is placed in group IIA of the periodic table along with St, Ba and Ra. The name calcium is derived from the Latin word “calas” meaning lime, which was known as early as the first centuries when the ancient Romans prepared lime as CaO. Calcium was isolated in 1808 by Sir Humphrey Davy of England who electrolyzed a combination of lime and mercuric oxide. Calcium (Ca) is yellowish to silvery-white and is considered hard.

Calcium is a metallic element and is the fifth most abundant in the Earth’s crust, where it constitutes more than 3% of the total. It is never found in its elemental form in nature. Calcium is a reactive alkaline earth metal that develops a dark oxide-nitride layer when exposed to air. Out of the alkaline earth group, Ca has achieved the greatest use and tonnage. It occurs abundantly as limestone (CaCO₃), gypsum (CaSO₄.2H₂O) and fluorite (CaF₂); where apatite is the fluorophosphate or chlorophosphate of calcium.

Role of Calcium in the Human Body

As a chemical element, calcium is important for living organisms, including humans, and is the most abundant mineral in the body vital for good health. This mineral is essential in muscle contraction, oocyte activation, building strong bones and teeth, blood clotting, nerve impulse, transmission, regulating heartbeat, and fluid balance within cells. Calcium requirements are paramount during pregnancy, breastfeeding, and childhood.

Long term calcium deficiency causes osteoporosis in which bones deteriorate and there is an increased risk of fractures. Extracellular calcium concentrations are controlled by parathyroid hormone, which stimulates the release of calcium from bones, and vitamin D, which promotes intestinal calcium absorption. Adults between the age of 19 to 64 require 700 mg of calcium a day.

Uses for Calcium

• Due to its strong affinity for oxygen and Sulphur, it is utilized as a cleanser for nonferrous alloys.
• As a deoxidizer, desulphurizer and decarburizer for various ferrous and nonferrous alloys, where it is implemented in the form of a stick or lump of metal.
• It is used as an alloying agent for aluminum, beryllium, copper, lead, and magnesium alloys.
• Serves as a ‘getter’ for residual gases in vacuum tubes.
• Crystalline calcium is employed in the form of a very reactive free-flowing powder of 94 to 97% purity and contains 2.5% calcium oxide (CaO) and smaller amounts of magnesium and these impurities.
• It can be used to harden lead.

Several Uses of Calcium Compounds in Food, Pharmaceuticals and Medical Industries

• Oyster shells (where the shell is CaCO₃) are a commercially important source of calcium for animal feeds.
• Edible calcium (calcium lactate, Ca(C₃H₅O₃)₂.5H₂O) for food products derived from milk.
• Calcium lactobionate, a white powder, used as a suspending agent in pharmaceuticals – containing 4.94% available calcium.
• Calcium diphosphate (commonly known as phosphate of lime) (CaHPO₄.H₂O) is soluble in dilute citric acid solutions and is used to add calcium and phosphorous to foods. It is also used as a polishing agent in toothpaste.
• Calcium monophosphate (CaH₄P₂O₈.H₂O) a stable, water-soluble white powder is used as a leaving agent in baking. The anhydrous form monocalcium phosphate (CaH₄(PO₄)₂) is used in pre-mixed flour mixes. Where each particle has a coating of a phosphate that has a time-dependent solubility to delay solution when liquids are added.
• Tricalcium phosphate (Ca₃(PO₄)₂) water-insoluble white powder, used to supply calcium and phosphorous to foods. Acts as a polishing agent in dentifrices, and as an antacid.

Important Calcium Compounds

• Calcium sulfate (CaSO₃.2H₂O), used to bleach paper pulp and textiles, it can also be used a disinfectant.
• Calcium silicate (CaO.SiO₂), used as a reinforcing agent in rubber. As an absorbent to control the viscosity of liquids. It can be employed as a filler in paints and coatings, and when used in coatings it can reduce sheen.
• Calcium metasilicate (CaO.SiO₃) or the mineral known as wollastonite, is a brilliant white powder and is therefore used in flat paints for paper coatings, as a filler plastic, as a coating for welding rods and for electrical insulators (tile and other ceramics).
• Calcium acetate (Ca(C₂H₃O₂) 2.H₂O) (also known as lime acetate, acetate of lime and vinegar salts) used in liming rosin and for the manufacture of metallic soaps and synthetic resins.
• Dolomite (a natural compound) is used directly as a flux in melting iron.
• Calcium silicide is implemented is the making of special steels to inhibit carbide formation.
• Calcium from limestone is an essential element in Portland cement

Edible Sources of Calcium

• Milk, cheese and other dairy products
• Green leafy vegetables –broccoli, cabbage and okra
• Soya beans, tofu
• Nuts and seeds, including pistachio, sesame, almonds, and hazelnuts
• Bread and anything made with fortified flour