Steps for purification of crude salt: 1, dissolution; 2, filtration (to remove insoluble impurities ); 3, add a slight excess of barium chloride; 4, filtration (to remove SO42- ions); 5, in the filtrate add sodium carbonate and sodium hydroxide; 6, filtration (to remove calcium, magnesium, and barium ions); 7, add an appropriate amount of hydrochloric acid to remove carbonate ions and hydroxide ions; 8, evaporation and crystallization to get pure sodium chloride crystals.

Steps for purification of crude salt

1, prepare equipment

Pallet balance (with weights), measuring cylinder, beaker, glass rod, medicine spoon, funnel, filter paper, iron stand (with iron ring), evaporating dish, alcohol lamp, crucible tongs, rubber-tipped burette. mortar, pestle and pestle, matches, a number of the same small pieces of paper

2. Dissolve

Weigh 2 grams of crude salt (to the nearest 0.1 gram) on a tray balance. Measure 10 ml of water with a measuring cylinder and pour it into a beaker. Take a spoonful of the coarse salt with a medicine spoon and add it to the water and stir with a glass rod; then add the coarse salt, stirring with the glass rod as you go, until the coarse salt is no longer dissolved.

3. Filtration

Adjust the ferrule to the proper position and place the beaker and filter. Glass rod leaning against the three layers of filter paper, funnel lower end of the mouth of the tube close to the inner wall of the beaker, beaker mouth leaning against the glass rod to divert the flow, the edge of the liquid surface is lower than the edge of the filter paper (in the production of filters, the filter paper should be close to the funnel) if the filtrate is turbid can be filtered again.

4, add a little too much BaCl?

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

5, add an excess of NaOH

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

6, add excess Na2CO3

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

7, Na2CO3+BaCl2=BaCO3↓+2NaCl

8, filtration

To the filtrate, add an appropriate amount of HCl (to remove excess NaOH, Na2CO3, optionally with a pH paper to control the amount added, or direct evaporation)

9, evaporation and crystallization to get pure sodium chloride crystals.