Properties:
NaCl, the main component of table salt, is an ionic compound. Pure sodium chloride crystals are colorless and transparent cubic crystals. Due to the presence of impurities, sodium chloride is generally white cubic crystals or fine crystal powders with a specific gravity of 2.165 (25/4°C) and a melting point of 801°C. Boiling point is 1442°C, relative density is 2.165 g/cubic centimeter, salty taste, easy to deliquesce when containing impurities; soluble in water or glycerol, insoluble in ethanol, insoluble in hydrochloric acid, aqueous solution is neutral and conductive.
Solid sodium chloride does not conduct electricity, but molten sodium chloride conducts electricity. Solubility in water increases slightly with increasing temperature. When the temperature is lower than 0.15 ℃, the dihydrate NaCl·2H2O can be obtained. Sodium chloride exists in large quantities in seawater and natural salt lakes. It can be used to produce chlorine, hydrogen, hydrochloric acid, sodium hydroxide, chlorate, hypochlorite, bleaching powder and metallic sodium, etc. It is an important chemical raw material;
It can be used for food seasoning, marinating fish, meat and vegetables, as well as for salting out soap and tanning leather, etc.; highly refined sodium chloride can be used to make physiological saline for clinical treatment and physiological experiments, such as sodium loss, loss of sodium, etc. Water, blood loss, etc. Sodium chloride can be produced by concentrating crystalline seawater or natural salt lake or salt well water.
Crystal structure: The unit cell is a face-centered cubic structure, and each unit cell contains 4 sodium ions and 4 chloride ions.
Uses:
Salt has a wide range of functions: sterilization, tooth protection, beautification, skin cleaning, decontamination, medical treatment, important chemical raw materials, edible...
1. Can react with silver nitrate to obtain silver chloride precipitation;
2. Solid table salt can be heated with concentrated sulfuric acid to obtain hydrogen chloride gas;
3. Electrolysis of chlorine Chlorine, hydrogen and sodium hydroxide can be obtained from sodium chloride solution;
4. Electrolysis of molten sodium chloride can obtain elemental sodium and chlorine.
Extended information
Related production methods
In industry, seawater is used to dry salt (also called salt field method) or well water or salt lake water is used to boil salt to make table salt. Crystals precipitate. The table salt produced in this way contains more impurities and is called coarse salt. Refined salt can be obtained from coarse salt through dissolution, precipitation, filtration and evaporation. There are also many people who add iodine in order to supplement more salt.
Physiological effects
Salt is indispensable in people’s lives. The total amount of sodium ions contained in the adult body is about 60 g, 80% of which is present in extracellular fluid, that is, in plasma and intercellular fluid. Chloride ions are also found mainly in extracellular fluid. The physiological functions of sodium ions and chloride ions mainly include the following points:
1. Maintain the osmotic pressure of extracellular fluid
Na and Cl are the main ions that maintain the osmotic pressure of extracellular fluid ; K and HPO4 are the main ions that maintain the osmotic pressure of intracellular fluid. Among the total cations in the extracellular fluid, Na accounts for more than 90%, and among the total anions, Cl accounts for about 70%. Therefore, salt plays an important role in maintaining osmotic pressure and affects the movement of water in the human body.
2. Participate in the regulation of acid-base balance in the body
Sodium bicarbonate formed from Na and HCO3 has a buffering effect in the blood. There is also a balance between Cl and HCO3 between plasma and red blood cells. When HCO3 penetrates from the red blood cells, the anions in the red blood cells decrease, and Cl enters the red blood cells to maintain the electrical balance. Vice versa, the same is true.
3. Chloride ions participate in the generation of gastric acid in the body
Gastric juice is highly acidic, with a pH of about 0.9 to 1.5. Its main components are pepsin, hydrochloric acid and mucus. Parietal cells in the corpus gastric glands secrete hydrochloric acid. Parietal cells transport HCO3 into the blood and secrete H into the gastric juice. At this time, Cl enters the gastric juice from the blood through the parietal cells to maintain electrical balance. Why can such strong hydrochloric acid not corrode the stomach wall in the stomach?
Because there is a kind of mucus cell in the gastric body gland, the secreted mucus forms a mucus layer about 1 mm to 1.5 mm thick on the surface of the gastric mucosa. This mucus layer is often called the barrier of the gastric mucosa. , under the attack of acid, the gastric mucosa will not be digested by digestive enzymes and form ulcers. However, drinking alcohol will weaken the barrier function of the gastric mucosa, often increasing the possibility of causing gastric ulcers.
In addition, salt also plays a role in maintaining the normal excitability of nerves and muscles.
When a large amount of extracellular fluid is lost (such as excessive bleeding, excessive sweating) or there is a lack of salt in the food, the content of sodium ions in the body is reduced, and potassium ions enter the blood from the cells, resulting in thickening of the blood, oliguria, and yellowing of the skin. and other diseases. The human body's requirement for salt is generally 3 g to 5 g per person per day. Due to different living habits and tastes, the actual salt intake varies greatly from person to place. The average person in my country consumes about 10 g to 15 g of salt every day.
Reference: Baidu Encyclopedia salt entry