How do you obtain pure sodium chloride from a crude sample?

Explanation

Crude sodium chloride, generally obtained by crystallisation of brine solution, contains sodium sulphate, calcium sulphate, calcium chloride and magnesium chloride as impurities. To get pure sodium chloride first the crude sodium chloride is dissolved in minimum amount of water and filtered to remove insoluble impurities.
Now into the saturated solution of sodium chloride hydrogen chloride gas is passed. Then pure sodium chloride crystallises. The other compounds which are present in small amounts such as `MgCl_(2)` and `CaCl_(2)` remain in solution.