In the purification of NaCl, an impure solution is saturated with HCl gas. The principle involved is:
Common ion effect and low solubility of MgCl2 and CaCl2 when compared to NaCl
Common ion effect and high solubility of MgCl2 and CaCl2 when compared to NaCl
KSP of NaCl is greater than that of MgCl2
KSP of NaCl is greter than that of CaCl2 but less than that of MgCl2
As Cl− concentration increases precipitation takes place.