Adding water to dissolve crude salt; Pour the supernatant into a funnel and filter; Put the filtrate in an evaporating dish and heat it to evaporate. This is a simple treatment, and the obtained salt crystals need to be further purified (crude salt generally contains many impurity ion compounds and halogen simple substances or compounds). The steps of crude salt purification in extended data

First of all, we filter the crude salt, which can remove insoluble impurities in the crude salt, add excessive barium chloride and remove sodium sulfate. Because of adding excessive barium chloride, barium chloride impurities are introduced.

Adding excessive sodium hydroxide to remove magnesium chloride, sodium hydroxide impurity is introduced due to excessive addition, and sodium carbonate impurity is introduced by adding excessive sodium carbonate to remove calcium chloride and residual barium chloride.

Then, an excessive amount of hydrochloric acid is added to remove the remaining sodium hydroxide and sodium carbonate, and the final step is huge evaporation and crystallization. Wait. So it's done.

Experimental phenomenon of crude salt purification

Dissolution: the crude salt solid is gray, and the liquid obtained by adding it into water is turbid.

Filtration: the filtrate is a colorless and transparent liquid, and the residue on the filter paper is black.

Evaporation: with heating, the amount of liquid in the evaporating dish decreases; When it evaporates to a certain extent, there is solid precipitation at the bottom of the evaporating dish. The solid obtained by evaporation is white.