Sodium chloride, chemical formula NaCl, colorless cubic crystal or fine-grained powder, containing salt. The appearance is white crystal, which is the main component of salt. Its source is mainly seawater, which is soluble in water and glycerol, slightly soluble in ethanol and insoluble in concentrated hydrochloric acid. Impure sodium chloride deliquesces easily in the air. Good stability. In industry, saturated sodium chloride solution is generally used to produce hydrogen, chlorine and caustic soda, and it can also be used for ore smelting, preparing physiological saline in medical treatment and flavoring in life.
physical features
Appearance and properties: colorless crystals or white powder.
Density: 2. 165g/cm? (25℃)
Refractive index: 1.378
Water solubility: 360 g/L (25? c)
Stability: stable under normal transportation and loading and unloading conditions.
Storage conditions: low temperature, ventilation and dryness in the warehouse.
Steam pressure: 1 mm? Hg？ (865 degrees Celsius)
Melting point: 80 1℃
Boiling point: 1465℃
Sodium chloride is a white and odorless crystalline powder. The melting point is 80 1℃ and the boiling point is 1465℃. Slightly soluble in ethanol, propanol and butane, it becomes plasma after being mixed with butane, but it is soluble in water, and its solubility in water is 35.9g (room temperature). NaCl can form colloid when dispersed in alcohol, and its solubility in water is reduced by the presence of hydrogen chloride, and it is almost insoluble in concentrated hydrochloric acid. Odorless, salty and deliquescent. Soluble in water, soluble in glycerol, almost insoluble in ether.
chemical property
Sodium chloride crystals form stereo symmetry. In its crystal structure, the larger chloride ions are arranged in the cube with the densest packing, and the smaller sodium ions fill the octahedral gaps between chloride ions. Each ion is surrounded by six other ions. This structure also exists in many other compounds, called sodium chloride structure or halite structure.
Sodium chloride test
First, the silver nitrate solution acidified by nitric acid was dropped into the sodium chloride solution to produce white precipitate, which proved that there was Cl-.
Second, dip a small amount of solution in platinum wire and burn it on an alcohol lamp. The flame is yellow, which proves that it contains Na+.
Third, in order to eliminate interference, it is advisable to add saturated barium hydroxide to the original test solution until it is obviously alkaline. At this time, most cations and PO43? 、AsO43？ The same ion will be precipitated. Ba2+ introduced into the test solution should be removed by ammonium carbonate, and finally ammonium salt should be removed by burning. After hot water extraction of the residue, acidify the solution with HAc, add zinc uranyl acetate reagent according to the number of drops 1:8, and rub the pipe wall with a glass rod. If there is lemon yellow crystal precipitation, it means that Na+ exists.
preparation method
1, industrial method
Introducing seawater into the salt field, drying in the sun, concentrating and crystallizing to obtain a crude product. Alternatively, seawater can be heated by steam, filtered by sand filter, concentrated by electrodialysis with ion exchange membrane to obtain brine, evaporated to separate brine gypsum, centrifugally separated to obtain sodium chloride over 95%, and then dried to obtain salt. Rock salt and salt lake brine can also be used as raw materials, and the raw salt can be dried. It is made from underground brine and well salt by three-effect or four-effect evaporation concentration, crystallization and centrifugal separation.
2. Laboratory methods
Dissolve crude salt in water, remove insoluble impurities, and add refined agents such as sodium hydroxide and sodium carbonate. Precipitating soluble impurities such as SO42-, Ca2+ and Mg2+, filtering to remove, finally adjusting the pH to 7 with pure hydrochloric acid, and concentrating the solution to obtain pure sodium chloride crystals. The preparation method in the laboratory is to mix equal amounts of hydrochloric acid and sodium hydroxide to generate sodium chloride solution. And then distilling the solution to obtain sodium chloride crystals.
Storage method
1. Precautions for operation: close the operation and strengthen ventilation. Operators must be specially trained and strictly abide by the operating procedures. It is recommended that the operator wear a self-priming filter dust mask, chemical safety glasses, gas-proof overalls and rubber gloves. Avoid dust. Avoid contact with oxidants. When handling, handle with care to prevent the packaging and containers from being damaged. Equipped with leakage emergency treatment equipment. Empty containers may leave harmful substances behind.
2. Precautions for storage: Store in a cool and ventilated warehouse. Stay away from fire and heat sources. Should be stored separately from oxidant, and should not be mixed. The storage area should be equipped with suitable materials to control leakage.