. How can sodium chloride be purified
Answer: The salt obtained by various manufacturing processes is contaminated. Hence, to purify sodium chloride, it is first of all treated with ammonium carbonate to precipitate down the carbonates of calcium and magnesium.
The solution is filtered to remove these precipitates and through the filtrate, hydrochloric acid is passed. As a result, sodium chloride settles down. This is found to be quite pure. Only KCl is present as impurity which is removed by repeated crystallisation