Formation process of calcium carbonate from highly supersaturated solution

Abstract The precipitation process of calcium carbonate from highly supersaturated solutions was observed in situ by mixing CaCl 2 and Na 2 CO 3 aqueous solutions at about 20°C under an optical microscope and an infrared microspectroscope. After an amorphous phase forms, spherulitic vaterite and calcite in a rhombohedral shape nucleate simultaneously but separately, and grow by forming the precipitate-free zone around them. This transformation is solvent-mediated, and the measurement of the growth rate suggests that the rate-controlling process is the diffusion of elements in the earlier stage of this process, which then changes to surface kinetics.