Table also shows that the inhibitory effect of additive Ca 2+ ions on CaCO 3 growth decreases with increasing C P and β. When β = 0.5 and C S = 10 mM, the particle hydrodynamic size increased by approximately 200 nm with each 25 mM increase in C P (Table ). This is due to the nucleation of more crystals at higher C P and β, which would require the presence of more additive Ca 2+ ions for improved growth inhibition. However, the concentration of additive Ca 2+ ions are limited as they irreversibly adsorb on the precipitates. The growth-inhibitory effect thus diminishes faster in higher C P and β conditions. Consequently, particles obtained in relatively high C S and β conditions form large aggregates to lower their interfacial tension and achieve equilibrium. They also sediment the moment the experiment ended.