Calcium is the chemical element with atomic number 20, symbol Ca
It is a fairly hard gray-white alkaline earth metal. Calcium does not exist as a pure body in nature. It is the fifth most abundant element in the earth’s crust (over 3%). It is vital for many species: formation of bones, teeth and shells (it makes up 1 to 2% of the weight of the human body of an adult). Calcium also plays a very important role in cellular physiology, while being a cellular poison beyond a certain dose.
Physical applications of calcium metal
- Reducing agent in the extraction of other metals such as uranium, zirconium, and thorium;
- deoxidizer, desulfurizer or decarburizer for various ferrous and non-ferrous alloys;
- used, sometimes in combination with magnesium, to remove bismuth from lead (deismuthage);
- alloying agent used in the production of alloys of aluminum, beryllium, copper, lead and magnesium.
Usage
Metallic calcium is used as a reducing agent in metallurgy for the production of metals such as thorium, vanadium, zirconium, yttrium and other rare earth metals , as a reducing agent in steel and aluminum production, as an alloy additive in aluminum, beryllium, copper, lead – and magnesium alloys and as a starting material for the production of calcium hydride.
The technical use of calcium takes place predominantly in bound form.
Limestone (mainly calcium carbonate, CaCO3) and dolomite (CaMg (CO3 ) 2 ) are two of the most important raw materials in today’s industry:
- Slagging agent in steel production . The consumption is 0.5 tons of limestone per ton of steel
- Raw material for the production of quick lime.
- Chalk as a filler for plastics, for example PVC . The aim is to improve stiffness and impact strength, as well as to reduce shrinkage. The also greatly increased thermal conductivity allows higher work cycles during extrusion.
- Fine-grain calcium carbonate is used as a filler in high-quality, wood-free paper.
- Finely ground lime or dolomite is used as fertilizer lime in agriculture and forestry or as fodder lime in animal husbandry.
Because of its functions in organisms, calcium is also used as a drug.
Here are some of the benefits of calcium for humans
Activates nerves
Blood circulation
Flex muscles
Normalizes blood pressure
Balance the acidity of the blood
Maintain body fluid balance
Prevent osteoporosis (bone loss)
Prevent heart disease
Reducing the risk of colon cancer
Overcoming cramps, back pain, hemorrhoids, and rheumatism
Overcoming complaints during menstruation and menopause
Minimizes bone loss during pregnancy and breastfeeding
Helps mineralization of teeth and prevents tooth root bleeding
Overcoming dry and cracked skin on the feet and hands
Restores decreased / weakened sex drive
Overcoming diabetes (activates the pancreas)
After the age of 20 years, the human body will begin to experience calcium deficiency as much as 1% per year. And after the age of 50 years, the amount of calcium content in the body will shrink by 30%. Losses will reach 50% when you reach the age of 70 years and thereafter experiencing calcium deficiency problems.
The initial symptoms of calcium deficiency include lethargy, profuse sweating, restlessness, shortness of breath, decreased endurance, lack of appetite, constipation, loose stools, insomnia, cramps, and so on.
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Recommended Calcium Intakes
| Age | Calcium (mg/day) |
|---|---|
| 1–3 years | 700 |
| 4–8 years | 1000 |
| 9–18 years | 1300 |
| 19–50 years | 1000 |
| >51 years | 1000 |
| Pregnancy | 1000 |
| Lactation | 1000 |
The FAO (Food and Agriculture Organization) nutritional recommendations are based on the relationships between calcium intake and calcium absorption and excretion, determined by an analysis of existing studies. Balance, according to the FAO, is reached with a daily intake of 520 mg taking into account the incompressible faecal losses, which rise to 840 mg taking into account the urinary losses and those related to desquamation, and to 1,100 mg when the Menopause-related losses are included.
Taking into account dietary intake of animal protein has a major effect on nutritional calcium requirements, the two being positively correlated14. It also helps to bring the recommended calcium intakes closer to the actual calcium intakes observed in a large part of the populations worldwide. Regarding sodium, if the salt intake in the diet were reduced, the calcium requirement could decrease to a level as low as 450 mg / d. Better attention to vitamin D levels (through sufficient exposure to the sun or through sufficient intake) could further reduce nutritional calcium requirements.
The recommended nutritional intake is finally 900 mg per day in adults who consume a Western diet. A WHO (World Health Organization) study shows that DRI (Dietary Reference Intake) vary significantly between developed countries. At the same time, the recommended daily allowance is 800 mg per day (for an adult woman).
According to the WHO and FAO, a much lower calcium requirement (500 mg / day) is observed in people with a much more vegetarian diet, who are sufficiently exposed to the sun (vitamin D) and who exercise non-sedentary. Indeed, the ingestion of sulfur amino acids (such as methionine) in large quantities would increase the loss of calcium in the urine. These sulfur amino acids are found in large quantities in meats, fish, eggs, cold cuts.
Consequences of excess calcium
A study of a population cohort in Sweden found higher mortality for women ingesting more than 1,400 mg of calcium per day, especially in supplement form. In addition, several studies establish a correlation between a high intake of calcium and a high incidence of prostate cancer.
Food sources
The United States Department of Agriculture (USDA) web site has a very complete searchable table of calcium content (in milligrams) in foods, per common measures such as per 100 grams or per a normal serving.
Food, calcium per 100 grams
| Food, calcium per 100 grams |
|---|
| parmesan (cheese) = 1140 mg |
| milk powder = 909 mg |
| goat hard cheese = 895 mg |
| Cheddar cheese = 720 mg |
| tahini paste = 427 mg |
| molasses = 273 mg |
| almonds = 234 mg |
| collard greens = 232 mg |
| kale = 150 mg |
| goat milk = 134 mg |
| sesame seeds (unhulled) = 125 mg |
| nonfat cow milk = 122 mg |
| plain whole-milk yogurt = 121 mg |
Food, calcium per 100 grams
| Food, calcium per 100 grams |
|---|
| hazelnuts = 114 mg |
| tofu, soft = 114 mg |
| beet greens = 114 mg |
| spinach = 99 mg |
| ricotta (skimmed milk cheese) = 90 mg |
| lentils = 79 mg |
| chickpeas = 53 mg |
| eggs, boiled = 50 mg |
| orange = 40 mg |
| human milk = 33 mg |
| rice, white, long-grain = 19 mg |
| beef = 12 mg |
| cod = 11 mg |
Measurement in blood
The amount of calcium in blood (more specifically, in blood plasma) can be measured as total calcium, which includes both protein-bound and free calcium. In contrast, ionized calcium is a measure of free calcium. An abnormally high level of calcium in plasma is termed hypercalcemia and an abnormally low level is termed hypocalcemia, with “abnormal” generally referring to levels outside the reference range.
| Target | Lower limit | Upper limit | Unit |
| Ionized calcium | 1.03, 1.10 | 1.23, 1.30 | mmol/L |
| 4.1, 4.4 | 4.9, 5.2 | mg/dL | |
| Total calcium | 2.1, 2.2 | 2.5, 2.6, 2.8 | mmol/L |
| 8.4, 8.5 | 10.2, 10.5 | mg/dL |
The main methods to measure serum calcium are:
- O-Cresolphalein Complexone Method; A disadvantage of this method is that the volatile nature of the 2-amino-2-methyl-1-propanol used in this method makes it necessary to calibrate the method every few hours in a clinical laboratory setup.
- Arsenazo III Method; This method is more robust, but the arsenic in the reagent is a health hazard.
The total amount of Ca2+ present in a tissue may be measured using Atomic absorption spectroscopy, in which the tissue is vaporized and combusted. To measure Ca2+ concentration or spatial distribution within the cell cytoplasm in vivo or in vitro, a range of fluorescent reporters may be used. These include cell permeable, calcium-binding fluorescent dyes such as Fura-2 or genetically engineered variant of green fluorescent protein (GFP) named Cameleon.
Corrected calcium
As access to an ionized calcium is not always available a corrected calcium may be used instead. To calculate a corrected calcium in mmol/L one takes the total calcium in mmol/L and adds it to ((40 minus the serum albumin in g/L) multiplied by 0.02). There is, however, controversy around the usefulness of corrected calcium as it may be no better than total calcium. It may be more useful to correct total calcium for both albumin and the anion gap.
Calcium in the periodic table
| Atomic number (Z) | 20 |
|---|---|
| Group | group 2 (alkaline earth metals) |
| Period | period 4 |
| Block | s-block |
| Electron configuration | [Ar] 4s2 |
| Electrons per shell | 2, 8, 8, 2 |
Physical properties
| Physical properties | |
|---|---|
| Phase at STP | solid |
| Melting point | 1115 K (842 °C, 1548 °F) |
| Boiling point | 1757 K (1484 °C, 2703 °F) |
| Density (near r.t.) | 1.55 g/cm3 |
| when liquid (at m.p.) | 1.378 g/cm3 |
| Heat of fusion | 8.54 kJ/mol |
| Heat of vaporisation | 154.7 kJ/mol |
| Molar heat capacity | 25.929 J/(mol·K) |
Vapour pressure
| P (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
|---|---|---|---|---|---|---|
| at T (K) | 864 | 956 | 1071 | 1227 | 1443 | 1755 |
Atomic properties
| Atomic properties | |
|---|---|
| Oxidation states | +1, +2 (a strongly basic oxide) |
| Electronegativity | Pauling scale: 1.00 |
| Ionisation energies |
|
| Atomic radius | empirical: 197 pm |
| Covalent radius | 176±10 pm |
| Van der Waals radius | 231 pm |
Other properties
| Other properties | |
|---|---|
| Natural occurrence | primordial |
| Crystal structure | face-centred cubic (fcc) |
| Speed of sound thin rod | 3810 m/s (at 20 °C) |
| Thermal expansion | 22.3 µm/(m·K) (at 25 °C) |
| Thermal conductivity | 201 W/(m·K) |
| Electrical resistivity | 33.6 nΩ·m (at 20 °C) |
| Magnetic ordering | diamagnetic |
| Magnetic susceptibility | +40.0·10−6 cm3/mol[4] |
| Young’s modulus | 20 GPa |
| Shear modulus | 7.4 GPa |
| Bulk modulus | 17 GPa |
| Poisson ratio | 0.31 |
| Mohs hardness | 1.75 |
| Brinell hardness | 170–416 MPa |
| CAS Number | 7440-70-2 |
History
| History | |
|---|---|
| Discovery and first isolation | Humphry Davy (1808) |
The name “calcium” is derived from the Latin word calx . This is how the Romans called lime, limestone, chalk and mortar made from lime ( building lime ).
Elemental calcium was first obtained by Humphry Davy in 1808 by evaporating the mercury from electrolytically obtained calcium amalgam.
Main isotopes of calcium
| Main isotopes of calcium | |||||||||||||||||||||||||||||||||||||||||||||||||||||
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Periodic Table of Elements | Complete List of Chemical Elements by Group, Name, Symbol, Color and Type
Sources: Royal Society of Chemistry
Photo credit: Wikimedia Commons
Photo explanations: Crystals of pure 99,99% Calcium. Crystals of calcium stored in a protective atmosphere.
