The raw salt is complex in composition, mainly composed of sodium chloride, and usually contains insoluble impurities such as precipitate and soluble impurities such as K+, Ca2+, Mg2+, SO42- and CO32-. The steps of crude salt purification are divided into:

1, dissolved;

2. Filtering (removing insoluble impurities);

3. Add a little excess barium chloride;

4. Filtering (removing SO42- ions);

5, adding sodium carbonate and sodium hydroxide into the filtrate;

6. Filtering (removing calcium, magnesium and barium ions);

7. Add a proper amount of hydrochloric acid to remove carbonate ions and hydroxide ions;

And 8, evaporating and crystallizing to obtain pure sodium chloride crystals.