Calcium is a metallic element, symbol Ca, located in the fourth periodic period of the chemical periodic table, Group IIA, and is a silvery-white crystal at normal temperature.
Animal bones, clams, and eggshells contain calcium carbonate. Alloy can be used for the deoxidizer, oils dehydrating agent, a reducing agent metallurgy, iron and iron alloys of desulfurization and decarbonization agent and an electron tube getter like.
Its compounds are very useful in industry, construction, and medicine.
A brief history of research
For a long time, chemists used calcium oxides obtained from the calcination of calcium carbonate containing limestone as unreplaceable substances.
It was listed in the element table published by Lavoisier in 1789. But despite this, David began the electrolysis of calcium oxide in 1808. The method that David just started to use was not ideal, so it was impossible to separate the metal calcium.
By May 1808, David was inspired by the experiment in which Bezilius and the Swedish Royal Doctor Pundin jointly electro calculated the mixture of quicklime and mercury.
He mixes the moist quicklime and oxidized mercury in a ratio of 3 to 1, and places it on a platinum sheet, which is connected to the positive electrode of the battery, and then makes a hole in the mixture, injects mercury, inserts a platinum wire, and the negative electrodes of the cells are connected to each other to obtain a larger amount of calcium amalgam.
After the calcium amalgam is distilled, silver-white metal calcium is obtained. From then on, calcium is identified as an element and is named calcium, and the element symbol is Ca. Calcium comes from the word calx in Latin which means quicklime.
Elemental release: The calcium content in the earth’s crust is 4.15%, which is the fifth. The main calcium-containing minerals are limestone CaCO3, dolomite CaCO3 ·MgCO3, fluorite CaF2, and the like. Eggshells, pearls, corals, some animal shells and soil contain calcium. Calcium chloride in seawater accounts for 0.15%.
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The main group of the family of the Periodic Table of the Elements. Silverish white is slightly softer
Metal, shiny. Insoluble in benzene, slightly soluble in alcohol, soluble in acid, liquid ammonia.
Calcium ( atomic mass unit: 40.078(4)) has a total of 24 isotopes, of which 5 are stable.
It reacts directly with most non-metals when heated, such as with sulfur, nitrogen, carbon, hydrogen to form Calcium Sulfide CaS, calcium nitride Ca 3N 2, calcium carbide CaC 2, and calcium hydride CaH 2.
Reacts with carbon dioxide when heated. It is chemically active and forms an oxide or nitride film on the surface of the air to slow down further corrosion.
It can be combined with oxygen to form calcium oxide, and combined with nitrogen to form calcium nitride Ca 3N 2, combined with fluorine, chlorine, bromine, iodine, etc. to form the corresponding halide, and hydrogen to form calcium hydride under the action of 400 °C catalyst.
It reacts with water at room temperature to form calcium hydroxide and emits hydrogen. It reacts with dilute sulfuric acid such as hydrochloric acid to form salt and hydrogen and reacts with carbon at a high temperature to form calcium carbide CaC 2.
Almost all metal oxides can be reduced upon heating, and many metal chlorides can be reduced upon melting.
Compound: Calcium is important compounds calcium hydride, calcium oxide, calcium peroxide, calcium chloride, calcium fluoride, calcium carbide, calcium hydroxide, calcium cyanamide, calcium carbonate, calcium hypochlorite, calcium sulfate and the like.
Calcium reacts with liquid ammonia to form Ca (NH 3) 6, which is a metallic solid conductive solid, calcium ions can form a chelate [CaEDTA] 2 — ( EDTA is ethylene diamine tetraacetic acid), calcium ions and containing N The compound with O atom can form a complex and form a macrocyclic complex with the crown ether and the hole ether.
Calcium fluoride CaF 2 is white crystal or powder, density 3.18 g / cm 3, melting point 1,418 °C, boiling point 2,533.4 °C, hardly soluble in water, soluble in strong concentrated inorganic acid to release hydrogen fluoride.
Natural calcium fluoride minerals are fluorite or fluorspar, often in the form of gray, yellow, green, purple and the like.
In the industry, calcium fluoride and hydrofluoric acid are commonly used for neutralization to prepare calcium fluoride, the waste gas obtained by using water to absorb calcium magnesium phosphate fertilizer is neutralized with lime milk, and calcium fluoride can also be obtained.
Calcium peroxide (CaO2) is a yellow-white crystal and belongs to the tetragonal system, density 2.9 g/cm3, heated to 275 ° C explosion decomposition easy to deliquesce, slightly soluble in water, and dilute sulfuric acid to form hydrogen peroxide.
Adding hydrogen peroxide and ammonia water to the calcium chloride aqueous solution, or dissolving calcium hydroxide and ammonium chloride in water, and then adding hydrogen peroxide, both reactions are carried out at about 0 °C, and CaO 2·8H 2 O crystals are precipitated, Dehydrated and dried at 150 to 200 °C to obtain anhydrous calcium peroxide.
It reacts violently with water at room temperature to form calcium hydroxide (lime) and hydrogen water.
Ca + 2H2O ==== Ca (OH)2 + H2 ↑(displacement reaction)
Soluble in acid, can decompose water and release hydrogen.
The relevant chemical equation for calcium:
Ca + 2HCl = CaCl2 + H2 ↑ (displacement reaction) N2 + 3Ca = Ca3N2 (combination reaction) 3C + CaO = CaC2 + CO ↑ (redox reaction) 2HNO3 + CaCO3 = Ca(NO3)2 + H2O + CO2 ↑(metathesis reaction) 2Cl2 + 2Ca(OH)2 = CaCl2 + Ca(ClO)2 + 2H2O (redox reaction) 2HF + CaCl2 = CaF2 + 2HCl (metathesis reaction) SiO2 + CaO = CaSiO3 (combination reaction) Ca(HCO3)2 = heating = CaCO3 + H2O + CO2 ↑ (decomposition reaction) CaCO3 = high temperature = CaO + CO2 ↑ (decomposition reaction)
Electrolysis Method: The dried anhydrous calcium chloride is put into the electrolytic cell, and the raw material beside the anode (graphite) in the electrolytic cell is sprayed with an oxyacetylene flame, that is the cooling water is opened, and the cathode (round steel) is put down, and the contact material is discharged.
The surface of the liquid is supplied with current. The molten feed is directed to the cathode to close the circuit. After the raw material is mostly melted, the new material is continuously added until it is 2 to 3 cm away from the tank, and the temperature is normal.
Metallic calcium is deposited on the cathode at a current of 350 to 450 A and a voltage of 20 to 25 V. The current should be reduced by 50 to 100 A before the metal calcium deposited on the cathode is struck.
After the metal calcium to be knocked is placed in the oil, the cathode is contacted with the electrolyte liquid surface, and the current is increased by 50 to 100 A.
In order to maintain the temperature of the electrolytic cell, the material should be continuously fed. Chlorine gas escapes from the anode and is recycled.
Calcium can be obtained by electrolysis and aluminothermic reduction. The molten salt of electrolytic calcium chloride has a purity of only 90%.
The thermal reduction method uses aluminum to reduce calcium oxide at a high temperature, and the product has a high purity (99%). The process is also relatively simple and is the method adopted in recent years.
First, CaO is obtained by calcination of calcium carbonate CaCO3. Aluminum is preferably a small particle or flake. The molar ratio of calcium oxide to aluminum is 3:2. The ingredients are mixed to form a preform.
The pressure of the manual hydraulic press can be lower than the pressure of the magnesium silicon preform.
Metallic calcium can be used to electrolytically melt calcium chloride at 780–800 °C.
The electrolytic cell may be graphite crucible, the anode is graphite, and the iron rod or graphite rod is used as a cathode. The current density of the cathode was maintained at 100 A/cm2.
As the metal calcium precipitates, the cathode is gradually increased. The metal calcium covers a layer of molten calcium chloride solidified in the air to prevent oxidation.
The calcium purity is 98% to 99%, and the impurities are iron, silicon, aluminum, trace amounts of carbon and some chlorine.
The limestone CaCO reacts with hydrochloric acid to obtain calcium chloride:
Causes of calcium deficiency:
Anorexia, partial eclipse not easy to fall asleep, easy to wake up; easy to catch a cold; hair thinning; mental retardation; toddler, late teeth or irregular teeth; paroxysmal abdominal pain diarrhea; X or O-leg; chicken breast.
Insufficient energy; easy to fatigue; back pain; low immunity; tooth decay or tooth dysplasia.
Pregnant women and lactating women
Cramps are weak; joint pain; dizziness; anemia and prenatal hypertension syndrome; edema and insufficient milk secretion.
Senile skin disease itching; heel pain, lumbar vertebrae, cervical vertebra pain, loose teeth, shedding, obvious hunchback, height reduction, loss of appetite, digestive ulcer, multiple dreams, insomnia, irritability, irritability, etc.
Scientific Calcium Supplementation:
Calcium supplement first depends on the calcium source, safety is the key, from the calcium source, there are mainly chemical calcium agents obtained by means of synthesis, extraction, etc. (calcium carbonate, calcium gluconate, calcium hydrogen phosphate, amino acid chelated calcium, bone calcium, etc. ) and two kinds of natural food calcium agents such as milk.
Milk is recognized as the best source of natural food calcium. It is a combination of mineral salts derived from calcium, dehydrated, degreased and dried.
Its ingredients include calcium citrate, calcium phosphate, and ionized calcium. Milk calcium does not require too much stomach acid to participate in the body to separate and present the ionic state, which is then directly absorbed and utilized by the human body, rapidly regulating blood calcium balance and enhancing physical fitness.
Calcium is recognized as the highest bioavailability food-grade calcium supplement in all calcium, because there is a proper amount of protein and reasonable calcium and phosphorus ratio in the milk calcium 2.1, at the same time, because there is no production process, there is no burden on the gastrointestinal tract in any chemical composition or process.
Therefore, milk calcium is the most suitable source of calcium for infants, pregnant mothers, children and the elderly.
After reading the calcium source, see the dosage form: There are more than forty kinds of calcium nutrition fortifiers. The dosage forms mainly include solid tablets, powders, granules, capsules, liquid liquids, emulsions, etc.
Since solid calcium must be decomposed by gastric acid, calcium is released from the complex and released into a soluble ionized state to facilitate absorption.
Therefore, generally solid calcium will have hidden dangers of a stomach injury, and there are gas, nausea and another discomfort. In comparison, liquid calcium is simpler, more direct, more easily absorbed, and safer because of the calcium ion release procedure.
A small number of multiple doses: according to the characteristics of the intestines “high intake, low absorption, low intake, and high absorption”, when taking calcium products, it is advisable to take more meals.
The amount of calcium to be taken is different depending on the age of the person, and the amount of each meal is generally suitable within 50 to 100 mg. Infants and young children should not exceed 50mg per meal, and adults and pregnant women should not exceed 100mg per meal. And choose to take between meals to reduce the interference of other foods.
Calcium supplementation method that is often overlooked:
The eggshell contains extremely high calcium. You can grind the eggshell into a powder and then sprinkle it into food or put it in white water to eat or drink, which is convenient for the body to absorb calcium.
Let’s take a look at the function and deficiency of calcium in the body.
99% of calcium is distributed in bones and teeth. Before the age of 20 is the growth stage of the bones, when you are a long time. People have two peak growth periods: before the age of 1 (calcium deficiency in children will lead to stunting, dysplasia, such as late teething, late toddler, and chicken breast) and 12 to 14 years old (small stature, growth pain).
After 20 years of age, bone quality is still increasing. 35 to 40 years old, bone density peaked. After the age of 40, bone calcium is gradually lost (the elderly will accelerate the loss of bone calcium, resulting in shorter body, osteoporosis and bone hyperplasia).
1% of calcium is distributed in the blood, interstitial fluid, and soft tissue. Maintaining blood calcium levels plays an important role in maintaining normal human life. The human body has a mechanism to maintain blood calcium levels.
There are two sources of blood calcium: calcium absorbed through the digestive tract and calcium in the bones (the bones are large reservoirs of human calcium, and when the calcium intake is insufficient, the warehouse emergency is used), which all secretes ascending blood calcium through the parathyroid glands. And calcitonin to regulate.
Calcium deficiency reduces the elasticity and toughness of soft tissues. Skin lack of elasticity appears loose, aging; eye lens lacks elasticity, easy to myopia, presbyopia; vascular instability and easy to harden.
Reducing the excitability of nerve cells, so calcium is a natural sedative. Calcium deficiency can cause neurological migraine (10%-20% of women), irritability, and insomnia. For babies, it can cause night terrors, nightingales and night sweats. Calcium deficiency can also induce ADHD in children.
Strengthen the conduction function of the nervous system. For example, if your hand touches a glass of water, it is very hot and will be put down very quickly. There is a nervous system in the middle: sensor (skin) — afferent nerve — central nervous system — efferent nerve — effector (muscle). How do feelings and impulses pass to nerve cells, and how do nerve cells pass out? There is a substance called neurotransmitter in the middle. Calcium contributes to the production and release of neurotransmitters.
Maintain normal stimulation of the muscles. Such as increased blood calcium can inhibit the excitability of muscles and nerves; when the blood calcium is lower than 70mg / L, the excitability of the neuromuscular is increased, and convulsions appear. Intestinal syndrome, dysmenorrhea in girls, and calcium deficiency are an important cause.
Reduces (regulates) the permeability of cells and capillaries. Calcium deficiency can lead to allergies, edema and so on.
Promote the activity of various enzymes in the body. In the absence of calcium, the secretion of gland cells is weakened. Calcium is also an activator of enzymes.
Maintain acid-base balance.
Participate in the blood coagulation process. Coagulation of blood is a complex process, one of which is prothrombin, active thrombin, in which calcium is required for activation.
Calcium deficiency at different ages:
Children: night terrors, nightingale, irritability, night sweats, anorexia, square skull, rickets, skeletal dysplasia, low immunity, easy infection.
Adolescents: soft legs, cramps, poor physical performance, fatigue, irritability, lack of energy, partial eclipse, anorexia, tooth decay, poor tooth development, susceptibility to colds, and allergies.
Young adults: regular burnout, fatigue, cramps, back pain, easy to catch a cold, allergies.
Maternal: calf licking, back pain, joint pain, edema, pregnancy-induced hypertension, etc.
Middle-aged and elderly: back pain, calf spasm, osteoporosis, and bone hyperplasia, osteomalacia, various types of fractures, hypertension, cardiovascular and cerebrovascular diseases, diabetes, stones, tumors, etc.
To determine the method of calcium deficiency in children:
The 6-month-old hair is white and fat. In recent days, she often cries and does not stop. Her performance is not as lively as before. My mother took him to the hospital for examination. The doctor decided that the hair was deficient in calcium. Why is this?
Because children grow rapidly, and there are few outdoor activities, less sun exposure, often cause insufficient absorption of calcium and lead to various calcium deficiency. Whether children are deficient in calcium can be judged from the following aspects:
1 Often manifests as sweating and has nothing to do with temperature, especially after sweating on the head, so that the head of the child is constantly rubbing the pillow, and the pillow is visible behind the skull.
2 Mental irritability, not interested in the surrounding environment, sometimes parents found that children are not as lively as before.
3 Night terrors, often suddenly wake up at night, crying.
4 The children after the age of 41 showed that the teeth were late, some children still had no teeth when they were 1 and a half years old, and the front door was closed late, often not closed after 1 year and a half.
5 The forehead is high, forming a square skull.
6 Often have beaded ribs, due to the lack of vitamin D, costal cartilage hyperplasia, cartilage hyperplasia of each ribs are like a bead-like, often pressure on the lungs, so that children with poor ventilation, prone to bronchitis, pneumonia.
When the child is severely deficient in calcium, the muscle-tendon is relaxed. If the muscles of the abdominal wall and the muscles of the intestine are loose, it can cause gas accumulation in the intestinal lumen and form an abdominal enlargement such as a frog belly. If the tendon of the spine is slack, a hunchback can occur. Calcium deficiency
After 1 year old, children learn to walk. If calcium is deficient, the bones will be softened. When standing, the bodyweight will bend the lower limbs. Some of them will be “X” shaped legs, some will be “O” shaped legs, and they are prone to fracture.
Eat more foods with high calcium content, such as milk, yogurt, cheese, loach, river bream, snail, shrimp, shrimp, kelp, fried fish, oysters, peanuts, sesame, tofu, pine nuts, kale, broccoli, cabbage, rape, etc.
Do more sports: exercise can pull muscles together, strongly stimulate bones, strengthen blood circulation and metabolism, and reduce calcium loss, delay bone aging, and help the body to absorb calcium in the diet.
More sun exposure: UV can promote the synthesis of VD in the body and facilitate the absorption of calcium. However, ultraviolet rays cannot penetrate the glass, so they cannot be exposed to the sun through the glass. Or use the ZZ-2 UV therapy device to illuminate the skin to promote calcium absorption.
Eat a good breakfast: the body has the strongest absorption of calcium in the morning.
For vegetables containing more oxalic acid, first, destroy the oxalic acid and then cook. Such as cabbage, broccoli, spinach, leeks, spinach, mustard, snow, bamboo shoots.
According to the 2002 “Nature Nutrition and Health of Chinese Residents” survey, the calcium deficiency in Chinese is still very serious. The daily intake of calcium in residents is 391 mg, which is only 41% of the recommended intake.