The precipitation of magnesium carbonate by the reaction of MgCl2 with Na2CO3, under the influence of polyacrylamide (PAM) was studied. Factors that affect the precipitation of magnesium carbonate, such as PAM concentration, reaction temperature, and stirring speed, were investigated comprehensively. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) methods were used to characterize the carbonate precipitate products. PAM concentration, reaction temperature, and stirring speed have significant effects on the morphology of the carbonate products. The product weight increases slightly with the increase in the amount of PAM added, but decreases slightly with the increase in the reaction temperature, and is almost irrelevant to the stirring speed. The products obtained at 25 and 50 degrees C were all identified as nesquehonite, MgCO(3 center dot)3H(2)O. At 75 degrees C an unidentified amorphous product forms. The use of an additive is found to be an effective method to adjust the morphology of magnesium carbonate. The information gained in this study would be helpful for the preparation of magnesium carbonate or other magnesium compounds with specific morphology. (C) 2010 Elsevier B.V. All rights reserved.