The invention relates to an improved process for obtaining Precipitated pure Calcium carbonate usable in pharmaceutical and related purposes from impure hydrated lime by Ammonium Chloride Route. In this process of formation of pure Calcium Carbonate, Ammonium Chloride and Carbon-di-oxide are used for purification and segregation. In this process of purification, Ammonium Chloride from Solution tank is allowed into the Reaction tank to react with the hydrated limo containing impurities like Iron oxide, Alumina, Silicate etc., and the end products ammonia, Calcium Chloride and water formed are processed through the filtration for removing the solid impurities and all the aludge and unwanted materials are separated and discharged. Then by introducing Carbon-di-oxide from Carbonation tank, the chemical reaction takes place to obtain pure Calcium Carbonate and Ammonium Chloride. Then Ammonium Chloride so separated is diverted back into the Solution tank for re-use in the system and Calcium Carbonate is washed, and filtered to obtain moisturized calcium Carbonate which is then dried to obtain pure, clean, dry and precipitated Calcium Carbonate with low impurity content suitable for direct use in Pharmaceutical Industry.