calcium

(kăl`sēəm) [Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839&degC;; b.p. 1,484&degC;; sp. gr. 1.55 at 20&degC;; valence +2. Calcium is a malleable, ductile, silver-white, relatively soft metal with face-centered, cubic crystalline structure. Chemically it resembles strontium and barium; it is classed with them as an alkaline-earth metalalkaline-earth metals,
metals constituting Group 2 of the periodic table. Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the
..... Click the link for more information. in Group 2 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
..... Click the link for more information. . Calcium is chemically active; it tarnishes rapidly when exposed to air and burns with a bright yellow-red flame when heated, mainly forming the nitride. It reacts directly with water, forming the hydroxide. It combines with other elements, e.g., with oxygen, carbon, hydrogen, chlorine, fluorine, arsenic, phosphorus, and sulfur, forming many compounds.

Although lime (calcium oxide) has been known since ancient times, elemental calcium was first isolated by Sir Humphry Davy in 1808. Today, calcium metal is usually prepared by electrolysis of fused calcium chloride to which a little calcium fluoride has been added. It is used in alloys with other metals, such as aluminum, lead, or copper; in preparation of other metals, such as thorium and uranium, by reduction; and (like barium) in the manufacture of vacuum tubes to remove residual gases.

The metal is of little commercial importance compared to its compounds, which are widely and diversely used. The element is a constituent of lime (see calcium oxidecalcium oxide,
chemical compound, CaO, a colorless, cubic crystalline or white amorphous substance. It is also called lime, quicklime, or caustic lime, but commercial lime often contains impurities, e.g., silica, iron, alumina, and magnesia.
..... Click the link for more information. ), chloride of lime (bleaching powder), mortarmortar,
in building, mixture of lime or cement with sand and water, used as a bedding and adhesive between adjacent pieces of stone, brick, or other material in masonry construction.
..... Click the link for more information. , plaster, cement (see cementcement,
binding material used in construction and engineering, often called hydraulic cement, typically made by heating a mixture of limestone and clay until it almost fuses and then grinding it to a fine powder.
..... Click the link for more information. , concreteconcrete,
structural masonry material made by mixing broken stone or gravel with sand, cement, and water and allowing the mixture to harden into a solid mass. The cement is the chemically active element, or matrix; the sand and stone are the inert elements, or aggregate.
..... Click the link for more information. , whitingwhiting,
white, powdery substance, prepared by grinding chalk or some other source of calcium carbonate. When mixed with linseed oil it forms putty, and with water and several other substances it constitutes whitewash.
..... Click the link for more information. , putty, precipitated chalkchalk,
mineral of calcium carbonate, similar in composition to limestone, but softer. It is characteristically a marine formation and sometimes occurs in great thickness; the chief constituents of these chalk deposits are the shells of minute animals called foraminiferans.
..... Click the link for more information. , gypsumgypsum
, mineral composed of calcium sulfate (calcium, sulfur, and oxygen) with two molecules of water, CaSO₄·2H₂O. It is the most common sulfate mineral, occurring in many places in a variety of forms. A transparent crystalline variety is selenite.
..... Click the link for more information. , and plaster of Paris. Tremolite, a form of asbestosasbestos,
common name for any of a variety of silicate minerals within the amphibole and serpentine groups that are fibrous in structure and more or less resistant to acid and fire.
..... Click the link for more information. , is a naturally occurring compound of calcium, magnesium, silicon, and oxygen. Calcium carbide reacts with water to form acetylene gas; it is also used to prepare calcium cyanamide, which is used as a fertilizer. The phosphate is a major constituent of bone ash. The arsenate and the cyanide are used as insecticides. Calcium bicarbonate causes temporary hardness in water; calcium sulfate causes permanent hardness. Generally, calcium compounds show an orange or yellow-red color when held in the Bunsen burner flame.

Although calcium is the fifth most abundant element in the earth's crust, of which it constitutes about 3.6%, it is not found uncombined. It is found widely distributed in its compounds, e.g., Iceland sparIceland spar,
colorless variety of crystallized calcite, characterized by its properties of transparency and double refraction. It is used chiefly in the manufacture of Nicol prisms, which are essential parts of polarizing microscopes and other optical instruments.
..... Click the link for more information. , marblemarble,
metamorphic rock composed wholly or in large part of calcite or dolomite crystals, the crystalline texture being the result of metamorphism of limestone by heat and pressure.
..... Click the link for more information. , limestonelimestone,
sedimentary rock wholly or in large part composed of calcium carbonate. It is ordinarily white but may be colored by impurities, iron oxide making it brown, yellow, or red and carbon making it blue, black, or gray. The texture varies from coarse to fine.
..... Click the link for more information. , feldsparfeldspar
or felspar
, an abundant group of rock-forming minerals which constitute 60% of the earth's crust. Chemically the feldspars are silicates of aluminum, containing sodium, potassium, iron, calcium, or barium or combinations of these elements.
..... Click the link for more information. , apatiteapatite
, mineral, a phosphate of calcium containing chlorine or fluorine, or both, that is transparent to opaque in shades of green, brown, yellow, white, red, and purple. Apatite is a minor constituent in igneous and metamorphic rocks.
..... Click the link for more information. , calcitecalcite
, very widely distributed mineral, commonly white or colorless, but appearing in a great variety of colors owing to impurities. Chemically it is calcium carbonate, CaCO₃, but it frequently contains manganese, iron, or magnesium in place of the calcium.
..... Click the link for more information. , dolomitedolomite
. 1 Mineral, calcium magnesium carbonate, CaMg (CO₃)₂. It is commonly crystalline and is white, gray, brown, or reddish in color with a vitreous to pearly luster. The magnesium is sometimes replaced in part by iron or manganese.
..... Click the link for more information. , fluoritefluorite
or fluorspar
, mineral appearing in various colors, e.g., green, yellow-brown, rose, and red. Chemically, it is calcium fluoride, CaF₂. Its crystals, commonly cubic, are transparent or translucent and under certain conditions exhibit fluorescence.
..... Click the link for more information. , garnetgarnet,
name applied to a group of isomorphic minerals crystallizing in the cubic system. They are used chiefly as gems and as abrasives (as in garnet paper). The garnets are double silicates; one of the metallic elements is calcium, magnesium, ferrous iron, or manganese and the
..... Click the link for more information. , and labradoritelabradorite
, a variety of plagioclase feldspar.
..... Click the link for more information. . It is a constituent of most plant and animal matter.

Calcium is essential to the formation and maintenance of strong bones and teeth; the recommended daily dietary allowance for all but young children ranges from 1,000 to 1,300 milligrams. In the human adult the bone calcium is chiefly in the form of the phosphate and carbonate salts. A sufficient store of vitamin D (see under vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
..... Click the link for more information. ) in the body is necessary for the proper utilization of calcium. Calcium also functions in the regulation of the heartbeat and in the conversion of prothrombin to thrombin, a necessary step in the clotting of blood.

Calcium

(Ca), a chemical element in group IIA of Mendeleev’s periodic table. Atomic number, 20; atomic weight, 40.08; a silver-white, lightweight metal. The natural element consists of a mixture of six stable isotopes: ⁴⁰Ca, ⁴²Ca, ⁴³Ca, ⁴⁴Ca, ^46Ca, and ⁴⁸Ca, the most abundant of which is the first (96.97 percent).

Calcium compounds, such as limestone, marble, and gypsum (as well as lime, the product of limestone calcination), have been used in construction since antiquity. Chemists considered lime to be an element as recently as the end of the 18th century, but in 1789 A. Lavoisier suggested that lime, magnesia, baryta, alumina, and silica are compound materials. H. Davy electro-lyzed a mixture of moist slaked lime and mercuric oxide in 1808 using a mercury cathode to prepare a calcium amalgam from which he removed the mercury by distillation and obtained a metal that he named calcium (from the genitive calcis of the Latin calx, “lime”).

Occurrence in nature. Calcium is the fifth most abundant element in the earth’s crust (after oxygen, silicon, aluminum, and iron): 2.96 percent by weight. It migrates vigorously and accumulates in various geochemical systems, forming 385 minerals (the fourth largest number of minerals formed by an element). The earth’s mantle contains little calcium and the earth’s core probably contains even less (iron meteorites contain 0.02 percent). Calcium predominates in the lower part of the earth’s crust, accumulating in basic rocks. A large amount of calcium is found in the feldspar anorthite, Ca[Al₂Si₂O₈]; basic rocks contain 6.72 percent and acidic rocks, such as granites, contain 1.58 percent. An extremely sharp differentiation of calcium takes place in the biosphere, principally because of the “carbonate balance,” by which the soluble bicarbonate Ca(HCO₃)₂ is formed from the reaction between carbon dioxide and calcium carbonate, CaCO₃: CaCO₃ + H₂O + CO₂ ⇆ Ca(HCO₃)₂ ⇆ Ca²⁺ + 2HCO^-₃. This reaction is reversible and the basis for the redistribution of the element. Calcium dissolves in water with a high CO₂ content, but at a low CO₂ content the mineral calcite (CaCO₃) precipitates to form large deposits of limestone, chalk, and marble.

Biogenic migration also plays a very large role in the history of the element. Calcium is chief among the metallic elements in living matter. Organisms are known that contain more than 10 percent calcium (more than carbon) and build their skeleton from calcium compounds (mainly CaCO₃); these include calcif-erous algae, many mollusks, echinoderms, corals, and rhizopods. Deposits of the skeletons of marine animals and plants lead to the accumulation of colossal masses of algal, coral, and other limestones, which, buried deep within the earth and mineralized, are transformed into various types of marble.

Large territories with damp climates (wooded zones, tundra) are characterized by a lack of calcium, which is readily leached out of the soils. This phenomenon is a cause of low soil fertility, low productivity and poor growth in domestic animals, and, frequently, of diseases of the skeleton. Liming of soils and supplemental feeding of domestic animals and birds are therefore of great importance. Conversely, CaCO₃ is poorly soluble in dry climates, and steppe and desert regions are therefore rich in calcium. Gypsum (CaSO₄⋅2H₂O) is frequently enriched in solonchak and salt lakes.

Rivers carry large quantities of calcium to the oceans; however, the calcium does not remain in the ocean water (average content, 0.04 percent) but concentrates in the skeletons of organisms and settles to the bottom after their death (mostly in the form of CaCO₃). Limestone sediments are widely distributed over the bottom of all oceans at depths to 4, 000 m (CaCO₃ dissolves at greater depths and organisms at those depths frequently suffer a calcium deficit).

Underground waters play an important role in the migration of calcium. In places they vigorously leach out CaCO₃ in masses of limestone, which results in the formation of karst and of caverns, stalactites, and stalagmites. Not only calcite but also calcium phosphates (for example, the Karatau phosphorite deposits in Kazakhstan) and dolomite (CaCO₃ ⋅MgCO₃) were widely deposited in the oceans of past geological epochs. Gypsum was deposited upon the evaporation of lagoons.

In the course of geologic history the biogenic formation of carbonate increased and the chemical precipitation of calcite decreased. The Precambrian oceans (more than 600 million years ago) contained no animals with limestone skeletons; these animals first became widespread in the Cambrian (corals, sponges). An explanation is found in the high CO₂ content of the Precambrian atmosphere.

Physical and chemical properties. The crystal lattice of the a-form of calcium (stable at ordinary temperatures) is face-centered cubic; a = 5.56 Å. Its atomic radius is 1.97 Å; the ionic radius of Ca²⁺, 1.04 Å. Its density is 1.54 g per cm³ (20°C). The hexagonal β-form is stable above 464°C; melting point, 851°C; boiling point, 1482°C; temperature coefficient of linear expansion, 22 × 10^-6 (0°-300°C); thermal conductivity at 20°C, 125.6 watts per m°K, or 0.3 calories per cm.sec«°C); specific heat capacity (0°-100°C), 623.9 joules per kg.°K), or 0.149 cal per g-°C); specific electrical resistivity at 20°C, 4.6 × 10 ^-8 ohm-m, or 4.6 × 10”6 ohm • cm; temperature coefficient of electrical resistivity, 4.57 × 10^-3 (20°C); modulus of elasticity, 26 giga-newtons per m² (2, 600 kilograms-force per mm²); tensile strength, 60 meganewtons per m² (6 kgf/mm²); elastic limit, 4 MN/m² (0.4 kgf/mm²); yield point, 38 MN/m² (3.8 kgf/ mm²); relative elongation, 50 percent; Brinell hardness, 200-300 MN/m² (20-30 kgf/mm²). Calcium of sufficiently high purity is ductile. It may be pressed, rolled, and cut.

The configuration of the outer electron shell of the calcium atom is 4s², so that calcium is divalent in its compounds. Calcium is very active chemically. At ordinary temperatures it reacts very readily with atmospheric oxygen and moisture; it is therefore stored in hermetically sealed vessels or under mineral oil. When heated in air or in oxygen it ignites, resulting in the formation of the basic oxide CaO. The calcium peroxides CaO₂ and CaO₄ also occur. Calcium reacts with cold water rapidly at first, but the reaction is then retarded because of the formation of a film of Ca(OH)₂. Calcium reacts vigorously with hot water and with acids, giving off H₂ (this does not occur with concentrated HNO₃). Calcium reacts with flourine at lower temperatures and with chlorine and bromine above 400°C, yielding CaF₂, CaCl₂, and CaBr₂, respectively. In the molten state these halides react with calcium to form the so-called subcompounds CaF and CaCl, in which the calcium is formally univalent. Heating calcium with sulfur yields calcium sulfide (CaS), which adds additional sulfur to give polysulfides, such as CaS₂ and CaS₄. Calcium reacts with dry hydrogen at 300°-400°C to give the hydride CaH₂, an ionic compound in which hydrogen is the anion. Calcium and nitrogen react at 500°C to give the nitride Ca₃N₂. The reaction of calcium with ammonia at low temperatures gives the complex ammoniate Ca[NH₃]₆. Heating calcium with silicon, phosphorus, or graphite in the absence of air gives calcium silicides (Ca₂Si, CaSi, and CaSi₂), calcium phosphide (Ca₃P₂), and calcium carbide (CaC₂), respectively. Calcium forms intermetallic compounds with aluminum, silver, gold, copper, lithium, magnesium, lead, and tin.

Production and uses. Calcium is produced industrially by two methods: (1) by heating a briquetted mixture of CaO and powdered aluminum at 1200°C in a vacuum of 0.01-0.02 mm Hg; the calcium vapors, evolved according to the equation 6CaO + 2A1 = 3CaO ⋅ A1₂O₃ + 3Ca, condense on a cold surface; (2) by electrolyzing a melt of CaCl₂ and KCl, using a liquid copper-calcium cathode, to give a copper-calcium alloy (65 percent calcium) from which the calcium is distilled at 950°-1000°C in a vacuum of 0.1-0.001 mm Hg.

The pure metal calcium is used as an agent for reducing uranium, thorium, chromium, vanadium, zirconium, cesium, rubidium, and some rare-earths from their compounds. Metallic calcium is also used for deoxidizing steels, bronzes, and other alloys, removing sulfur from petroleum products, dehydrating organic liquids, removing nitrogenous impurities from argon, and as a gas absorber in electrovacuum instruments. Antifrictional materials based on a lead-sodium-calcium system and lead-calcium alloys for the fabrication of electric-cable sheaths are used widely in industry. A calcium-silicon-calcium alloy (silicocalcium) is used as a deoxidizing agent and degasifier in the production of high-quality steels. The uses of calcium compounds are described in separate articles.

A. IA. FISHER and I. A. PEREL’MAN

Calcium in the organism. Calcium is one of the biogenic elements, that is, elements that are necessary for the normal progress of the life processes. It is present in all tissues and fluids in animals and plants. Only rarely are organisms capable of developing in an environment lacking in calcium. In some organisms the calcium content is as high as 38 percent; in man, the content is 1.4-2 percent. The cells of plants and animals require strictly fixed proportions of Ca²⁺, Na⁺, and K⁺ ions in the extracellular fluids. Plants obtain calcium from the soil. Plants are divided into the calcephiles and calcephobes, depending on their behavior toward the element. Animals obtain calcium from food and water.

Calcium is essential for the formation of a number of cell structures, for the maintenance of the normal permeability of the outer cell membranes, for the fertilization of the egg cells of fish and other animals, and for the activation of a number of enzymes. Ca²⁺ ions transmit stimuli to muscle fiber and bring about its contraction, they increase the strength of cardiac contractions, they increase the phagocytic function of leukocytes, they activate the immunoprotein system in blood, and they participate in blood coagulation. Almost all of the calcium in cells is present in the form of compounds with proteins, nucleic acids, phospholipids, and complexes with inorganic phosphates and organic acids. In the blood plasma of man and the higher animals as little as 20-40 percent of the calcium may be combined with proteins. In animals with skeletons as much as 97-99 percent of the calcium is used as structural material: in invertebrates, mainly in the form of CaCO₃ (the shells of mollusks and corals), and in vertebrates, mainly as phosphates. Many invertebrate animals store calcium for the construction of a new skeleton prior to shedding their shells or for providing for the vital functions in unfavorable conditions.

The calcium content of human blood and the blood of other higher animals is regulated by hormones of the parathyroid and thyroid glands. Vitamin D plays an important role in these processes. Calcium absorption takes place in the anterior section of the small intestine. Calcium assimilation decreases when the acidity of the intestinal tract is lowered and is a function of the calcium-phosphorus-fat ratio in the food. The optimum ratios of calcium to phosphorus are about 1.3 in cow’s milk, 0.15 in potatoes, 0.13 in beans, and 0.016 in meat. In cases of excess phosphorus or oxalic acid in the food, calcium absorption decreases. Absorption is accelerated by the bile acids. For man, the optimum proportion of calcium to fat in food is 0.04-0.08 g Ca to 1 g fat.

The elimination of calcium takes place mainly through the intestinal tract. Mammals lose large quantities of the elementwith their milk during lactation. Upsets in phosphorus-calciummetabolism in young animals and children lead to rickets, andin adults, to changes in the composition and structure of theskeleton (osteomalacia).

I. A. SKUL’SKII

In medicine. The use of calcium preparations eliminates disturbances related to a deficiency of Ca²+ ions in the body (for example, in tetanus, spasmophilia, and rickets). Calcium preparations reduce increased sensitivity to allergens and are used in the treatment of allergic conditions (serum allergy, nettle rash, angioneurotic edema, hay fever). They lower increased permeability of the blood vessels and have an anti-inflammatory effect. They are used for hemorrhaging vasculitis, radiation sickness, inflammatory and exudative processes (pneumonia, pleuritis, endometritis), and certain skin conditions. They are prescribed to control bleeding, improve the activity of heart muscle, and reinforce the action of digitalis preparations. They are used as weak diuretics and as antitoxins in cases of magnesium-salt poisoning. Jointly with other drugs, they are used to stimulate labor. Calcium chloride is prescribed orally and intravenously. Ossocal-cinol (a 15-percent sterile suspension of a specially prepared bone meal in persic oil) is suggested for tissue therapy.

Calcium preparations also include gypsum (CaSO₄), which is used in surgery for casts, and chalk (CaCO₃), which is prescribed for internal use in cases of elevated gastric acidity and for the preparation of tooth powder.

REFERENCES

Kratkaia khimicheskaia entsiklopediia, vol. 2. Moscow, 1963. Pages 370-75.
Rodiakin, V. V. Kal’tsii, ego soedineniia i splavy. Moscow, 1967.
Kaplanskii, S. Ia. Mineral’nyi obmen. Moscow-Leningrad, 1938.
Vishniakov, S. I. Obmen makroelementov u sel’skokhoziaistvennykh zhi-votnykh. Moscow, 1967.

calcium

[′kal·sē·əm] (chemistry) A chemical element, symbol Ca, atomic number 20, atomic weight 40.08; used in metallurgy as an alloying agent for aluminum-bearing metal, as an aid in removing bismuth from lead, and as a deoxidizer in steel manufacture, and also used as a cathode coating in some types of photo tubes.

calcium

a malleable silvery-white metallic element of the alkaline earth group; the fifth most abundant element in the earth's crust (3.6 per cent), occurring esp as forms of calcium carbonate. It is an essential constituent of bones and teeth and is used as a deoxidizer in steel. Symbol: Ca; atomic no.: 20; atomic wt.: 40.078; valency: 2; relative density: 1.55; melting pt.: 842±2°C; boiling pt.: 1494°C

calcium

(Ca) [kal´se-um] a chemical element, atomic number 20, atomic weight 40.08. (See Appendix 6.) Calcium is the most abundant mineral in the body. In combination with phosphorus it forms calcium phosphate, the dense, hard material of the bones and teeth. It is an important cation in intracellular and extracellular fluid and is essential to the normal clotting of blood, the maintenance of a normal heartbeat, and the initiation of neuromuscular and metabolic activities.
Within the body fluids calcium exists in three forms. Protein-bound calcium accounts for about 47 per cent of the calcium in plasma; most of it in this form is bound to albumin. Another 47 per cent of plasma calcium is ionized. About 6 per cent is complexed with phosphate, citrate, and other anions.
Ionized calcium is physiologically active. One of its most important physiological functions is control of the permeability of cell membranes. Parathyroid hormone, which causes transfer of exchangeable calcium from bone into the blood stream, maintains calcium homeostasis by preventing either calcium deficit or excess.
Hypercalcemia: This is when the level of serum calcium rises above normal; neuromuscular activity begins to diminish. Symptoms include lethargy, muscle weakness (which, as the level of calcium increases, can progress to depressed reflexes and hypotonic muscles), constipation, mental confusion, and coma. The heartbeat also slows, which potentiates the effects of digitalis.
Hypocalcemia: This is a serum level of calcium that is below normal; it is manifested by increased neuromuscular irritability. When there is a deficit of ionized calcium, the nerve cells become more permeable, allowing leakage of sodium and potassium from the cells. This produces excitation of the nerve fibers and triggers uncontrollable activity of the skeletal muscles. Hence, as the calcium level continues to drop, the patient begins to experience muscle twitching and cramping, grimacing, and carpopedal spasm, which can quickly progress to tetany, laryngospasm, convulsions, cardiac arrhythmias, and eventually to respiratory and cardiac arrest. Relatively early signs of hypocalcemia are a positive trousseau's sign and a positive chvostek's sign.
Dietary sources of calcium include dairy products (such as milk and cheese), soybeans, fortified orange juice, dark green leafy vegetables (such as mustard greens and broccoli), sardines, clams, and oysters. The allowance" >recommended dietary allowance of calcium for children aged 4 to 8 is 800 mg, and that for women aged 50 to 70 is 1200 mg. (See tables in the Appendices for recommended dietary allowances across the life span.) It is difficult to meet these requirements without including milk or milk products in the daily diet. The most familiar calcium deficiency disease is rickets, in which the bones and teeth soften. However, it is believed that a large number of people suffer from subclinical calcium deficiency because of poor eating habits. Since calcium is essential to the formation and maintenance of strong bones, an adequate intake is important in the prevention of osteoporosis.calcium acetate the calcium salt of acetic acid; administered orally as a source of calcium and as a binder" >phosphate binder, such as in patients with end-stage renal disease. Also used as a pharmaceutical buffering agent.calcium carbonate an insoluble salt occurring naturally in bone, shells, and chalk; used as an antacid, calcium supplement, and binder" >phosphate binder, and for treatment of osteoporosis.calcium channel blocker (calcium channel blocking agent) a drug such as nifedipine, diltiazem, or verapamil that selectively blocks the influx of calcium ions through a channel" >calcium channel of cardiac muscle and smooth muscle cells; used in the treatment of angina" >Prinzmetal's angina, chronic angina" >stable angina, and cardiac arrhythmias" >arrhythmias. Calcium channel blocking agents act to control arrhythmias by slowing the rate of sinoatrial node discharge and the conduction velocity through the atrioventricular node. They act in vasospastic angina to relax and prevent coronary artery spasm. The mechanism of action in classical angina is a lowering of myocardial oxygen utilization by dilating peripheral arteries and thereby reducing total peripheral resistance and the work of the heart.

Physiologic activity of calcium channel blockers. (Data from Hardman J. and Limbird L., editors: Goodman and Gilman's The Pharmacologic Basis of Therapeutics, 9th ed., New York, McGraw-Hill, 1996; and the National Institutes of Health: The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, NIH Pub. No. 98-4080, Washington, DC, GPO, 1998.) From Edmunds and Mayhew, 2000.calcium chloride a salt used in solution to restore electrolyte balance, treat hypocalcemia, and act as a treatment adjunct in cardiac arrest and in magnesium poisoning.calcium citrate a salt used as a calcium replenisher; also used in the treatment of hyperphosphatemia in osteodystrophy" >renal osteodystrophy.calcium glubionate a calcium replenisher, used as a nutritional supplement and for the treatment of hypocalcemia; administered orally.calcium gluceptate a calcium salt administered intramuscularly or intravenously in the prevention and treatment of hypocalcemia and as an electrolyte replenisher.calcium gluconate a calcium salt administered intravenously or orally in the treatment and prevention of hypercalcemia and as a nutritional supplement. It is also administered by injection as a treatment adjunct in cardiac arrest and in the treatment of hyperkalemia.calcium hydroxide an astringent compound used topically in solution or lotions.calcium lactate a calcium replenisher, administered orally in the treatment and prevention of hypocalcemia and as a nutritional supplement.calcium oxalate a salt of oxalic acid, which in excess in the urine may lead to formation of oxalate calculi" >urinary calculi.calcium oxide lime (def. 1).calcium pantothenate a calcium salt of the dextrorotatory isomer of the B vitamin pantothenic acid; used as a nutritional supplement. It is also available as racemic calcium pantothenate, which is a mixture of the dextrorotatory and levorotatory isomeric forms.calcium phosphate a salt containing calcium and the phosphate radical; dibasic and tribasic calcium phosphate are used as sources of calcium.calcium polycarbophil a hydrophilic agent used as a bulk laxative.calcium propionate a salt used as an antifungal preservative in foods and as a topical antifungal agent.calcium pyrophosphate the pyrophosphate salt of calcium, used as a polishing agent in dentifrices. Crystals of the dihydrate form occur in the joints in calcium pyrophosphate deposition disease.calcium pyrophosphate deposition disease an acute or chronic inflammatory arthropathy caused by deposition of crystals of calcium pyrophosphate dihydrate in the joints and synovial fluid and chondrocalcinosis. Clinically, it may resemble numerous other connective tissue diseases such as arthritis and gout, or it may be asymptomatic. Acute attacks are sometimes called pseudogout.calcium sulfate a compound of calcium and sulfate, occurring as gypsum or as plaster of paris.

cal·ci·um (Ca),

, gen.

cal·'ci·i

(kal'sē-ŭm, -sē-ī), A metallic bivalent element; atomic no. 20, atomic wt. 40.078, density 1.55, melting point 842°C. The oxide of calcium is an alkaline earth, CaO, quicklime, which on the addition of water becomes calcium hydrate, Ca(OH)₂, slaked lime. For some organic calcium salts not listed below, see the name of the organic acid portion. Many calcium salts have crucial uses in metabolism and in medicine. Calcium salts are responsible for the radiopacity of bone, calcified cartilage, and arteriosclerotic plaques in arteries. [Mod. L. fr. L. calx, lime]

calcium

A bivalent metallic element (atomic number 20; atomic weight 40.08) that is critical for bone and tooth formation and intimately linked to many metabolic processes, including muscle contraction, neural transmission, coagulation and inhibition of cell destruction. Calcium levels in the blood are controlled by the balanced action of parathyroid hormone and calcitonin. It is present in dairy products, almonds, leafy greens, sardines and salmon; proper absorption of calcium hinges on appropriate acidity of the stomach, presence of vitamin D and a balance of other minerals, including phosphorus and mangesium.

calcium

A metal, atomic number 20, atomic weight 40.08, which is a divalent cation abundant in the body, especially in bone and teeth Calcium metabolism Ca2+ is the most critical mineral in bone–added by osteoblasts; removed by osteoclasts, Ca2+ maintains metabolic processes–eg, muscle contraction, neural transmission, cardiac activity, coagulation and inhibition of cell destruction; serum Ca2+ levels are controlled by a balance between PTH and calcitonin–produced by the thyroid's C or parafollicular cells; proper absorption of Ca2+ hinges on appropriate gastric acidity, presence of vitamin D, and a balance of other minerals–eg, phosphorus and mangesium; PTH ↑ serum Ca2+ levels by ↑ bone resorption via osteoclasts and mobilizing Ca2+, and indirectly ↑ GI absorption of Ca2+ by ↑ vitamin D production; PTH also ↑ phosphate excretion in the urine; calcitonin ↓ serum Ca2+ and phosphate levels by inhibiting bone resorption Daily requirement ± 400–1000 mg/day Ref range Infant to 1 month: 7.0-11.5 mg/dL; 1 month to 1 yr: 8.6-11.2 mg/dL >1 yr: 8.2-10.2 mg/dL; chronic abuse of laxatives, excess transfusions and various drugs can ↓ Ca2+ levels; Ca2+ is ↑ in hyperparathyroidism, parathyroid tumors, Paget's disease, myeloma, metastatic CA, multiple Fx, prolonged immobilization, renal disease, adrenal insufficiency, ↑ Ca2+ ingestion, antacid abuse; Ca2+ is ↓ in Cushing syndrome, hypoparathyroidism, malabsorption, acute pancreatitis, renal failure, peritonitis. See Hypercalcemia, Hypocalcemia, Ionized calcium.

cal·ci·um

(Ca) (kal'sē-ŭm) A metallic bivalent element; atomic no. 20, atomic wt. 40.078, density 1.55, melting point 842°C. Many calcium salts have crucial uses in metabolism and in medicine. Calcium salts are responsible for the radiopacity of bone, calcified cartilage, and arteriosclerotic plaques in arteries. [Mod. L. fr. L. calx, lime]

calcium

(kal'se-um) [ calci- + -ium] Ca A silver-white metallic chemical element, atomic number 20, atomic weight (mass) 40.08. Lime (calcium oxide), CaO, is its oxide. Calcium is a major component of limestone. Hydroxylapatite, a calcium phosphate, makes up about 75% of body ash and about 85% of mineral matter in bones.

Function

Calcium is important for blood clotting, enzyme activation, and acid-base balance. It gives firmness and rigidity to bones and teeth. It is essential for lactation, the function of nerves and muscles (including heart muscle), and maintenance of membrane permeability. Most absorption of calcium occurs in the duodenum and is dependent on the presence of calcitriol. Dietary factors affecting calcium absorption include phytic acid, consumption of too much phosphorus, and polyphenols found in tea. Approximately 40% of the calcium consumed is absorbed. Blood levels of calcium are regulated by parathyroid hormone; deficiency of this hormone produces hypocalcemia. The serum level of calcium is normally about 8.5 to 10.5 mg/dl. Low blood calcium causes tetany. Blood deprived of its calcium will not clot. Calcium is deposited in the bones but can be mobilized from them to keep the blood level constant when dietary intake is inadequate. At any given time, the body of an adult contains about 700 g of calcium phosphate; of this, 120 g is the element calcium. Adults should consume at least 1 g of calcium daily. Pregnant, lactating, and postmenopausal women should consume 1.2–1.5 g of calcium per day.

Sources

Excellent sources of calcium include milk and milk products (but not cottage cheese), and calcium-fortified orange juice. Good sources include canned salmon and sardines, broccoli, tofu, rhubarb, almonds, figs, and turnip greens.

CAUTION!

1. Laboratory error and variation may sometimes cause inaccurate or inconsistent values in evaluating calcium levels.

CAUTION!

2. Excessive calcium supplementation has been associated with a small increased risk of vascular calcification and heart attack. CAS # 7440-70-2 See: hypercalcemia; hypocalcemia; osteoporosis

calcium-45

⁴⁵Ca A radioactive isotope of calcium, half-life 164 days.

calcium chloride

CaCl₂·2H₂O, a salt used to raise the calcium content of the blood in disorders such as hypocalcemic tetany or overdose of calcium channel blocker or beta blocker. It is used in solution and administered intravenously. It is incompatible with epinephrine. CAS # 10043-52-4

calcium cyclamate

C₆H₁₂NNaO₃S, an artificial sweetening agent. See: cyclamate

calcium disodium edetate

A substance used to bind metallic ions, such as lead or zinc. It is used to treat poisoning caused by those metals.

calcium gluconate

C₁₂H₂₂CaO₁₄, a granular, white, odorless, and flavorless powder used to treat hypocalcemia, or overdose by calcium channel blocker or by beta blocker. CAS # 299-28-5

calcium glycerophosphate

C₃H₇CaO₆P, the calcium salt of glycerophosphoric acid. It is used as a dietary supplement, in drug formulation, and to prevent dental caries. CAS # 27214-00-2

calcium hydroxide

Ca(OH)₂, a white powder used as an astringent applied to the skin and mucous membranes and in dentistry as cavity liner or a pulp-capping material under a layer of zinc phosphate. It induces tertiary dentin formation for bridging or root closure, but it may be related to a chronic pulpitis and pulp necrosis after pulp capping. CAS # 1305-62-0

CLASSIC DIHYDRATE CALCIUM OXALATE CRYSTALS: (Orig. mag. ×400)

CALCIUM OXALATE CRYSTALS IN URINE: (Orig. mag. ×400)

calcium oxalate

CaC₂O₄, a compound containing calcium, present in urine in crystalline form. It is a constituent of some kidney stones. See: illustrationCAS # 25454-23-3illustration

calcium pantothenate

A salt of pantothenic acid, commonly used in vitamin supplements. Biochemically, it transfers acetyl groups from one compound to another. Egg yolks, liver, and yeasts are nutritional sources.

calcium saccharin

An artificial sweetening agent. See: saccharin

total serum calcium

The sum of the soluble and protein-bound calcium in the blood.

calcium tungstate

CaWO₄, a fluorescent material formerly used for radiologic imaging. It was used in intensifying screens to amplify the image, thereby reducing the radiation exposure to the patient.

calcium

A mineral present in large quantity in the body, mainly in the form of calcium phosphate in the bones and the teeth. Electrically charged calcium atoms (ions) are present in the blood and body fluids and are essential for many physiological processes including cell membrane permeability, cell excitability, the initiation and transmission of electrical impulses, muscle contraction, cell shape and cell motility. Calcium is necessary for blood coagulation, the production of ATP, and enzyme actions. Calcium levels in the blood are kept withing narrow limits by feedback mechanisms. Brand names of preparations containing calcium used to treat OSTEOPOROSIS are Ostram and Sandocal.

calcium (Ca)

an essential element to all animals and plants and a constituent of shells, bones and teeth.

Calcium

A silvery-yellow metal that is the basic element of lime and makes up about 3% of the earth's crust. It is the most abundant mineral in the human body. Calcium and phosphorous combine as calcium phosphate, the hard material of bones and teeth.Mentioned in: Bone Density Test, Hypercalcemia

cal·ci·um

(Ca) (kal'sē-ŭm) A metallic bivalent element; salts useful in metabolism and in medicine; responsible for radiopacity of bone, calcified cartilage, and arteriosclerotic arterial plaques in arteries. [Mod. L. fr. L. calx, lime]

Patient discussion about calcium

Q. It will be fine for my dad to take calcium as extra supplement; It will be fine for my dad to take calcium as extra supplement; as his bones are getting weak…. How much calcium intake is necessary for him?A. Older men need more calcium, because, as they age, the body becomes less efficient at absorbing calcium and other nutrients. Intake amount can’t be judged without age and weight and other body conditions are known. Please don’t give supplements without doctor’s prescription as the chances of overdose are more problematic.

Q. My sister has been having major allergy problems.How could she get her desired calcium? My sister has been having major allergy problems. Now she has developed an allergy and cannot tolerate milk in any form. None of our family members had allergic reactions to milk and my sister very recently developed this symptom. Is there any possibility of this symptom linked with any other illness? How could she get her desired calcium intake required by the body? Can you make any suggestions please?A. calcium is a very important part of our diet. lack of it will have a damaging effect. so it's good that you are aware!
many good sources of calcium exist. These include seaweeds such as kelp, wakame . nuts and seeds (like almonds and sesame). blackstrap molasses, beans, oranges, figs, quinoa , broccoli...
and another thing that you may do is crush an egg shell into powder and just mix a bit with her food. it's an excellent source.

Q. I'm concerned that my calcium supplements are contaminated w seashells or cow bones. Which brands are best A. there should be labeled as "from animal source".
here is something that helped me choose:
http://www.mayoclinic.com/health/calcium-supplements/AN00964

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REFERENCES

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cal·ci·um (Ca),

cal·'ci·i

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Function

Sources

CAUTION!

CAUTION!

calcium-45

calcium chloride

calcium cyclamate

calcium disodium edetate

calcium gluconate

calcium glycerophosphate

calcium hydroxide

calcium oxalate

calcium pantothenate

calcium saccharin

total serum calcium

calcium tungstate

calcium

calcium (Ca)

Calcium

cal·ci·um

Patient discussion about calcium

calcium

Synonyms for calcium

noun a white metallic element that burns with a brilliant light

Synonyms

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