Rock Salt from salt production methods performed by Akram fresh water to dissolve salt in Rock Salt. Then pump the slurry was purified by adding NaOH solution with Na2CO3 to get rid of Ca2 + and Mg2 + in reaction Mg2 + (AQ) + 2OH- (AQ) ® Mg (OH) 2 (s) Ca2 + (AQ) + CO32- (AQ) ®. CaCO3 (s)