step

1. Take the salt and dissolve it.

2. Add excessive BaCl2 (sulfate ion removal) BaCl2+Na2SO4==BaSO4↓+2NaCl.

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

4. Add excessive Na2CO3 (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 addition amount with pH test paper or directly evaporate).

7. Evaporative crystallization

The specific process of evaporation

Pour the obtained clear filtrate into an evaporating dish. Place the evaporating dish on the iron ring of the iron frame and heat it with alcohol lamp. At the same time, the filtrate is continuously stirred with a glass rod (evenly heated to prevent liquid splashing).

When a large number of solids appear in the evaporating dish, stop heating. The waste heat of the evaporating dish is used to evaporate the filtrate.

Experimental phenomenon

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

Filtration: the filtrate is 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.