Specific Surface Area Particles obtained in lower pH conditions are larger, and would have higher surface areas; however, Figure shows the BET SSA decreased with decreasing pH. This indicates the particles are less porous in low pH conditions, which is also evident in the SEM micrographs (Figure ). The micrographs show the particle surfaces become smoother with decreasing pH. It suggests the ability of additive Ca 2+ ions to attack growth sites on the crystals diminishes with decreasing pH. The presence of pores in particles syn- thesized in high alkaline pH environment is further confirmed in Figure (inset). This is the N 2(g) adsorption-desorption isotherm of CaCO 3 particles obtained without pH adjustment (pH = 12.5). It is a Type IV isotherm, having a H3 hysteresis loop, indicating the presence of mesopores. The average pore size was measured as ∼5 nm.