Colloidal pathways of amorphous calcium carbonate formation lead to distinct water environments and conductivity

Materials

All solutions were prepared using Milli-Q water that was degassed by bubbling N₂ through the solution overnight to remove dissolved CO₂. 20 mM CaCl₂ and 20 mM NaOH solutions were prepared by dilution of CaCl₂ stock solution (1.0 M, VWR, AVS Titrinorm volumetric solution) and NaOH stock solution (0.1 N, Carl Roth), respectively. Carbonate buffer solutions were freshly prepared before each experiment by dissolving Na₂CO₃ (Sigma-Aldrich, ACS grade, 99.95–100.05%) and NaHCO₃ (Sigma-Aldrich, ACS grade, >99.7%) in appropriate ratios for the desired pH value (pH 9.0, 9.4, 9.8,…