First, the experimental steps:

1, measure 10 ml of water with a measuring cylinder and pour it into a beaker. Add the crude salt into the water with a medicine spoon and stir it with a glass rod to observe the phenomenon. Then add the crude salt and stir it with a glass rod while adding it until the crude salt is no longer dissolved. Observe whether the solution becomes turbid.

2. Add excessive BaCl2 (to remove sulfate ions). BaCl2+Na2SO4==BaSO4↓+2NaCl.

3. Add excess NaOH (remove magnesium ions) MgCl2+2NaOH==Mg(OH)2↓+2NaCl.

4. Add excessive Na2CO3 (to remove calcium ions and barium ions in BaCl2) Na2CO3+CaCl2==CaCO3↓+2NaCl.

5、 Na2CO3+BaCl2==BaCO3↓+2NaCl

6 filtration

Add an appropriate amount of HCl to the filtrate (to remove excess NaOH NaOH,Na2CO3, you can choose to control the added amount with pH test paper or directly evaporate).

7. Evaporative crystallization

Second, the experimental phenomenon:

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

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

3. 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.

Third, the experimental conclusion

In the purification of crude salt, the residues on the filter paper are BaSO4, Mg(OH)2, CaCO3 and sediment. The filtrate is colorless and transparent.