What are the steps of crude salt purification? What is the principle of impurity removal? What is the sequence of adding reagents to remove impurities?

Filtering: Adjust the iron ring to a proper position and put it into a beaker and filter. The glass rod leans against the three layers of filter paper, the nozzle at the lower end of the funnel leans against the inner wall of the beaker, and the mouth of the beaker leans against the glass rod to drain water. The edge of the liquid level is lower than the edge of the filter paper (the filter paper should be close to the funnel when making a filter). If the filtrate is turbid, it can be filtered again.

The clarified filtrate insolubles remain on the filter paper.

HCl is added first, and then excess BaCl2 is added.

White precipitate BaSO4↓ appeared.

BaCl2+NaSO4= BaSO4↓+NaCl

Filter, and then adding excess Na2CO3.

White precipitate BaCO3↓CaCO3↓ appears.

Na2CO3+ BaCl2= BaCO3↓+NaCl

Na2CO3+Ca(OH)2= CaCO3↓+H2O+CO2

Filter, and then add excess NaOH.

White precipitate Mg(OH)2↓ appeared.

Sodium hydroxide+magnesium chloride = magnesium hydroxide ↓+sodium chloride

Filter and add HCl.

Burst out suddenly.

HCl+ Na2CO3= NaCl+H2O+CO2

Hydrochloric acid+sodium hydroxide = sodium chloride +H2O

(1) The "Four Principles" are: 1. No increase (no new impurities are added in the purification process); Not reducing (not reducing the substance to be purified); Three easy separation (purified products and impurities are easy to separate); Easy to recycle (the purified substance should be recycled).

Order:

Adding excessive BaCl2 (removing sulfate ions) SO42-+Ba2+=BaSO4↓

Add excess NaOH (remove magnesium ions) Mg2++2OH-=Mg(OH)2↓

Adding excessive Na2CO3 (removing calcium ions and barium ions in BaCl2)

Ca2 ++ CO32-= CaCO3↓Ba2 ++ CO32-= BAC O3↓