A mass restriction principle has been applied for the synthesis of precipitated calcium carbonate (PCC) with particle sizes from nanometer to micrometer via a simple emulsion liquid membrane (ELM) process. The internal liquid droplets in ELM were designed as individual microreactors in which the concentration and the total mass of the reaction chemicals were carefully mediated. Instrumental analysis, such as Fourier transform infrared (FTIR), wide X-ray diffraction (WXRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis, confirmed a predominant calcite form of the final product via this process. The comparison of calculated particle sizes with that obtained from experimental measurements using dynamic light scattering (DLS), transmission electron microscopy (TEM) and SEM analysis suggested that approximately one PCC particle was formed in one water-in-oil (w/o) droplet. (C) 2004 Elsevier Inc. All rights reserved.