Purification of coarse salt:

First dissolve the coarse salt in water,

then filter (note one stick, two low and three stick),

Then add excess bacl2 solution to remove na2so4: bacl2 na2so4==baso4↓ 2nacl

Then add excess naoh solution to remove mgcl2: mgcl2 2naoh==mg(oh)2↓ 2nacl

Then add excess na2co3 solution to remove cacl2 and bacl2 (two reaction equations): na2co3 cacl2==caco3↓ 2nacl

na2co3 bacl2==baco3↓ 2nacl

Filtration

Finally, add an appropriate amount of hydrochloric acid dropwise until gas is no longer produced, and remove naoh and na2co3 (you can use pH test paper to detect the pH, and there are also two reaction equations): hcl naoh==nacl h2o

2hcl na2co3==2nacl h2o co2↑

Evaporate the solution and precipitate nacl crystals.