Industrial methods
Seawater (with an average content of 2.4% sodium chloride) is introduced into the salt pan, dried by the sun, concentrated and crystallized, and crude products are prepared. Seawater can also be heated by steam, filtered by sand filter, and concentrated by ion exchange membrane electrodialysis to obtain brine (containing sodium chloride 160~180 g/L) by evaporation to precipitate salt halide gypsum, centrifugal separation, and more than 95% sodium chloride (2% moisture) prepared by drying. Rock salt and salt lake brine can also be used as raw materials, and the raw salt can be prepared by sun drying. When underground brine and well salt are used as raw materials, they are prepared by three-effect or four-effect evaporation and concentration, precipitation crystallization, and centrifugal separation.
Laboratory methods
The crude salt is dissolved in water to remove insoluble impurities, and then refined preparations such as sodium hydroxide and sodium carbonate are added to make soluble impurities such as SO42-, Ca2+, Mg2+ and other soluble impurities become precipitates, filtered and removed, and finally the pH is adjusted to 7 with pure hydrochloric acid, and the concentrated solution is pure sodium chloride crystallization.
In the laboratory, the preparation method is to mix an equal amount of hydrochloric acid with sodium hydroxide to produce a sodium chloride solution. The solution is then distilled to obtain sodium chloride crystals. Main reaction: HCl + NaOH = NaCl + H20.
In addition, sodium metal ignition in the environment of chlorine gas will also produce sodium chloride, the chemical equation is: 2Na + Cl2 = 2NaCl.
