The kinetic and thermodynamic simulations suggest that the dimerization process in neutral waters is facilitated by this fourth species. In the reaction zone, the formation of OSAZ was found to be energetically more favored than H3SiO4 -. Thus, it is proposed that the neutral pH dimerization rate depends on the formation of OSAZ, whose concentration is influenced mainly by ionic strength. Only upon the elevation of pH where the concentration of H3SiO4 -attains a sufficient level that the basic mechanism takes over. . Figure . Auto-ionization with salt present. Mechanism from OSAZ (H) to H3SiO4 -+H3O + (J) optimized with the B3LYP method. Atoms depicted by ball-and-stick are centers that use the higher level 6-311++G(d,p) basis sets. The rest of the atom centers use 6-31+G(d) basis sets. Corresponding energy changes are shown in Table . Figure . PES Diagram. The letters correspond to configurations in Figure and 8. Energies are in kJ/mol. Solid lines are for uncorrected internal energies and dashed lines are for zero point corrected internal energies. All energies are referenced to the internal energy of configuration G.