Fig. 9: The change in Si concentration with time in multi-stage experiment KGDB-70-1. The solid line is a fitting of equations (23) and (29) to the experimental data of stage B (stirred) and C (non-stirred), respectively. The regression coefficient of the fitting, R2 is 0.94. The dotted and the dashed lines illustrate the sensitivity of the fitting to the value of the product of the dissolution rate of the ultra-fine particles and their specific surface area (see text).