Sodium chloride A.R. & B.P. from marine salt

Abstract

The major impurities in marine salt are magnosium sulphate,magnesium chloride and calcium sulphate.the manufacture of analar and british pharmacopoeia (R.P.) grade sodium chloride must involve the quantitative removal of all the impurities from salt. various methods have been described for the removal of calcium, magnesium and sulphate ions. in one method , calcium and magnesium are removed by treatment with disodium hydrogen phosphate and sodium carbonate, followed by the elimination of sulphate ions by barium chloride.in another method barium chloride is used to precipitate sulphate ions: hydrogen peroxide is employed to oxidise iron, and sodium carbonate, to remove alkaline earth metals. the ph is then adjusted to 6.5 to ramove aluminium, magnesium and silicon compounds, followed by fractional crystallisation to obtain pure sodium chloride pure sodium chloride is olso obtained by the treatment of saturated salt solution with chlorine, followed by two successive precipitations by hydrochloric acid, and fusion of air dried product.