Effect of pH and Type of Stirring on the Spontaneous Precipitation of CaCO3 at Identical Initial Supersaturation, Ionic Strength and a(Ca2+)/a(CO32?) Ratio

CaCO3 precipitation is physical-chemical basis of biomineral formation hard tissue (shells, skeletons) in marine calcifying organisms (=biomineralization). Processes controlling biomineralization are still not fully clarified, so the study influence pH on basic processes should contribute to better understanding under climate change. This paper reports effect initial (pH0) and type stirring (mechanical magnetical) spontaneous phase composition, size morphology spontaneously precipitated formed at identical supersaturation, ionic strength a(Ca2+)/a(CO32?) ratio. The varied a range 8.50 ? pH0 10.50 included values relevant for mimicking conditions related organisms. In all systems two polymorphs were found: calcite and/or vaterite. increase favoured rhombohedral no matter stirring. was exclusively influenced by systems’ (other parameters identical). Furthermore, caused change vaterite from cauliflower-like spheroids regular spherulites. mechanically stirred produced larger particles higher content calcite.