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The calcium carbonate(CaCO3) is one of the most abundant biominerals.In addition CaCO3 has such industrial fields as rubber,dentifrice,polish,paint,dye,ink,paper,cosmetic,composite materials,etc.The application of CaCO3 particles is determined by a number of strictly defined parameters,such as morphology,structure,size,specific surface area,brightness,oil adsorption,chemical purity,and so on.One of the most important parameters is particle morphology.In this study,aragonite was synthesized using the calcium chloride process and calcium sulfate process,a liquid-liquid reaction.Especially,Mg2+,which was known to be the most effective ion for aragonite synthesis,was added th investigate th synthesis characteristics of aragonite.Morphology of calcium carbonate was changed by temperature and concentration of additives.Distilled water was used in this work.The precipitation of CaCO3 was carried out in 500ml glass beaker at different temperature according to the method reported by literatures respectively.First,A solution of Na2CO3(0.05M,100ml) CaCl2(0.05M,100ml) and Na2SO4(0.05M,100ml) (NH4)2CO3 was prepared as stock solutions.A solution of MgCl2(100ml) was injected into a solution of CaCl2(0.05M,100ml).Then a solution of MgCl2(0.05M,100ml) was injected into the Na2CO3(0.05M,100ml) solution and Na2SO4(0.05M,100ml) solution for 10min.The solution was kept under static conditions of 24hour before the product was collected for characterization.Separated particles by the membrane filter were dried in the oven(JOHNSAM).The products were characterized using scanning electron microscopy(SEM) and X-ray diffraction(XRD).When magnesium chloride was added,aragonite were formed Na2CO3(0.05M,100ml) CaCl2(0.05M,100ml) and Na2SO4(0.05M,100ml) (NH4)2CO3.As the concentration of magnesium chloride was increased,the production of calcite decreased rapidly and aragonite production increased.In particular,aragonite Na2SO4(0.05M,100ml) (NH4)2CO3 process was batter then Na2CO3(0.05M,100ml) CaCl2(0.05M,100ml) processs for aragonite production ratio.