Crude salt purification

Steps

1. Take salt, dissolve

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

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

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

5. Na2CO3+BaCl2==BaCO3↓+2NaCl

6 Filtration

Add appropriate amount of HCl (to remove excess NaOH, Na2CO3, you can choose to use pH paper to control the amount added, or direct evaporation)

7. Evaporation of crystals

The specific process of evaporation

The obtained clarified filtrate was poured into the evaporation dish. Place the evaporating dish on the iron ring of the iron stand and heat it with an alcohol lamp. At the same time, the filtrate is constantly stirred with a glass rod (uniform heating to prevent splashing of the liquid).

Wait until a large amount of solid appears in the evaporating dish and stop heating. Use the residual heat of the evaporating dish to vaporize the filtrate.

Experimental phenomena

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

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

Evaporation: the amount of liquid in the evaporating dish decreases as it is heated; when it evaporates to a certain extent, a solid precipitates from the bottom of the dish. The solid obtained by evaporation is white in color.