synonymNA(Chemical element sodium) generally refers to sodium (metal element)
Sodium is a metal element with the element symbol Na, and its English name is Sodium.In the periodic table, it is located in the third cycle, Group IA, and is the representative of alkali metal elements. It is soft and can react with water to generate sodium hydroxide, which emits hydrogen. Its chemical properties are relatively active.
Sodium is widely distributed in land and sea in the form of salt. Sodium is also one of the important components in human muscle tissue and nerve tissue.Sodium in the body is about 77~100g, accounting for 0.15% of the body weight, of which extracellular fluid accounts for 45%~50%, intracellular 9%~10%, and bone 40%~47%.
After Volt invented the battery at the beginning of the 19th century, chemists all over the world succeeded in using the battery to decompose water.Humphrey David, a British chemist, has been persistently engaged in experimental research on the use of batteries to decompose various substances.He melts by electrolysissodium carbonateObtained inMetallic sodium[1]。 David named sodium Sodium, because sodium is obtained from sodium carbonate (Soda), which still remains in English.The chemical symbol Na of sodium comes from its Latin name Natrium.
Sodium explodes in soil
Physical and chemical properties
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physical property
Sodium is a silver white cubic metal, soft and light, which can be cut with a knife, and its density is 0.968g/cm less than that of waterthree, melting point 97.72 ℃, boiling point 883 ℃.Its crystal structure is a body centered cubic lattice which is combined by sodium atoms through metal bonds.Since each sodium atom has only one valence electron, its solid molar atom volume is large, so the metal bond bonding force in its crystal is weak, which makes the metal sodium have very low density, hardness and melting point.The new section has silvery white luster, which turns to dark gray when oxidized in the air.Sodium is a good conductor of heat and electricity, with good magnetic conductivity. Potassium sodium alloy (liquid) is a heat conductor for nuclear reactors.There are more active free electrons in the metal crystal of sodium, so it has good conductivity.Under the action of light, electrons gain energy and escape from the metal surface to produce photoelectric effect[2]。Sodium also has good ductility and low hardness, and can be dissolved in mercury and liquid ammonia to form blue solution.Hardened at - 20 ℃[3]。
There are 22 kinds of sodium isotopes found, including Na-18 to Na-37, of which only Na-23 is stable, and other isotopes are radioactive[4]。
Cutting metal sodium
chemical property
Sodium is one of the most active metal elements in the periodic system, which has high reactivity.It can directly interact with nonmetallic elements with greater electronegativity, such as oxygen, sulfur, nitrogen, hydrogen, halogen, etc., generally forming ionic compounds.Combined with oxygen at room temperature and heating (4Na+Otwo2NatwoO，2Na+OtwoNatwoOtwo）, react violently with water (2Na+2HtwoO2NaOH+Htwo↑), explosion occurs in case of large quantity.Sodium can also be burned in carbon dioxide (2Na+2COtwoNatwoCOthree+CO), and liquid ammonia with weak ionization ability can also react (2Na+2NHthree（L）2NaNHtwo+Htwo↑）。
The outermost layer of sodium atom has only one electron, which is easy to lose, so it has strong reducibility.Therefore, sodium has a very active chemical property, which can react with a large number of inorganic substances, most non-metallic simple substances and most organic substances, and act as a reducing agent when oxidation-reduction reactions occur with other substances.At high temperatures, sodium can capture oxygen in oxides or chlorine in chlorides and reduce metals.For example: TiC1+4NaTi+4NaC1.Although sodium is expensive, it is still used in the production of rare metals as a reducing agent.Sodium is used as a reducing agent in organic synthesis. It can react with alcohol, ether and other organic reagents to produce sodium organic compounds.（2Na+2ROH2RONa+Htwo↑）
Sodium and its ions have the characteristic flame color yellow, so flame reaction is often used to test them in analytical chemistry.
Sodium reacts with water
Industrial use
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1. As a reducing agent: in the national defense industry, it is used to reduce titanium, zirconium, niobium, tantalum and other metals from their molten halides[5]。
2. As chemical raw materials: it is used to produce a variety of sodium containing compounds, including sodium butadiene rubber, sodium hydride, sodium peroxide, sodium cyanide and sodium carbonate. These compounds are used in many industries such as food, biology, pharmacy, rubber, leather, chemical, fire protection, ceramics, glass and water treatment[5-7]。
3. Alloy manufacturing: sodium amalgam of sodium and mercury alloy is used as a reducing agent for organic synthesis, sodium lead alloy is used for the production of gasoline antiknock agent, and sodium potassium alloy is used as a coolant and heat exchanger for nuclear reactors.
4. As an electric light source, high-pressure sodium lamp is widely used for highway lighting because of its yellow light and fog penetration.
5. As an isotope: Na-24 is radioactive and used for radioactive tracer analysis in biological research.
6. Application in the food industry: as a neutralizer and leavening agent, it is used in the production of amino acids, soy sauce and flour products, as well as in the neutralization of microorganisms in the process of noodle making[7]。
7. Application in glass industry: it is used for making water glass, sodium dichromate, sodium nitrate and other chemicals, and it is also one of the key raw materials for glass production[7-8]。
8. Application in metallurgical industry: used as smelting flux, flotation agent for mineral processing, and desulfurizer for steelmaking and antimony smelting.
9. Application in leather industry: used for degreasing of raw hides, neutralizing chrome tanned leather and improving the alkalinity of chrome tanning liquor.
10. Application in printing and dyeing industry: used as water softener.
Physiological function
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Sodium is an important inorganic element in the human body. Generally, the content of sodium in adults is about 3200 (female) - 4170 (male) mmol, accounting for 0.15% of the body weight. The content of sodium in the body is mainly in extracellular fluid, accounting for 44% - 50% of the total sodium, 40% - 47% in bones, and only 9% - 10% in intracellular fluid.
1. Sodium is the main positively charged ion in extracellular fluid, participating in water metabolism, ensuring the balance of water in the body, and regulating water and osmotic pressure in the body.
2. Maintain the balance of acid and base in the body.
3. It is a component of pancreatic juice, bile, sweat and tears.
4. Sodium is related to the production and utilization of ATP (adenine nucleoside triphosphate), muscle exercise, cardiovascular function, and energy metabolism. In addition, sodium is also involved in sugar metabolism and oxygen utilization.
5. Maintain normal blood pressure.Reducing sodium intake in diet is positively related to lowering blood pressure[9]。
6. Enhance neuromuscular excitability.The balance of sodium, potassium, calcium and magnesium ions plays an important role in maintaining neuromuscular excitability[9]。
Sodium generally exists in all kinds of food. Generally, animal food is higher than vegetable food. However, human sodium mainly comes from table salt, sodium or sodium containing compounds (such as glutamic acid, sodium bicarbonate, etc.) added in the process of food processing and preparation, as well as soy sauce, salted or pickled meat or smoked food, pickled vegetables, fermented bean products, salty snack food, etc.
Manifestations of sodium deficiency
In general, sodium in the human body is not easy to lack, but in some cases, such as fasting, eating less, dietary sodium restriction is too strict and intake is very low, or high temperature, heavy physical labor, excessive sweating, gastrointestinal diseases, repeated vomiting, diarrhea causes excessive sodium excretion and loss, or some diseases, such as Addison's disease, cause kidney unable to retain sodium effectively,When parenteral nutrition is deficient or low in sodium, sodium deficiency can be caused by the use of diuretics to inhibit renal tubular reabsorption of sodium.The lack of sodium is not obvious in the early stage, which is manifested as fatigue, indifference, apathy, and even fainting when standing up.When sodium loss is more than 0.5g/kg body weight, nausea, vomiting, decreased blood pressure, painful muscle spasm may occur, and no chloride is detected in urine.
Manifestation of sodium excess
Normally, too much sodium intake does not accumulate, but in some special cases, if salt is added to baby milk powder by mistake as sugar, it may cause poisoning or even death.Long term excessive dietary sodium intake may be manifested as hypertension.Long term intake of high amount of salt increases the risk of gastric cancer.Acute sodium overdose can be manifested as thirst, irritability, edema, delirium, and even death[9]。Acute poisoning can lead to edema, increased blood pressure, increased plasma cholesterol, decreased fat clearance, and damage to gastric mucosal epithelial cells.One gram of salt contains about 400 milligrams of sodium.The appropriate intake of sodium for adults is 2200 mg/d, that is, 5.5 grams of salt.The recommended daily intake of salt for international and Chinese diet is less than 5g.
Storage method
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Immersed in liquid paraffin, mineral oil and benzene series and sealed for preservation, a large number of them are usually stored in iron drums filled with argon for sealing preservation.Metal sodium cannot be preserved in kerosene because it reacts with organic acid and other substances in kerosene to form organic acid sodium and other substances (yellow) and adheres to the sodium surface[10]。When stored in paraffin oil, the oxygen in the air will also enter the paraffin oil, making the surface of metal sodium gray and forming an oxide film.
In case of small amount of storage with low purity requirements, it can be soaked in kerosene, such as laboratory storage.Store in a cool and dry place, away from kindling, heat source and flammable substances.A small amount is usually kept in liquid paraffin.It is stored and transported separately with oxidants, acids and halogens.
Fire extinguishing: graphite powder, sodium carbonate powder and calcium carbonate powder can be used.Water and halogenated hydrocarbon fire extinguishing are prohibited.
