『Abstract
　The dissolution and precipitation rates of boehmite, AlOOH, at 100.3℃ and limited precipitation kinetics of gibbsite, Al(OH)3, at 50.0℃ were measured in neutral to basic solutions at 0.1 molal ionic strength (NaCl + NaOH + NaAl(OH)4) near-equilibrium using a pH-jump technique with a hydrogen-electrode concentration cell. This approach allowed relatively rapid reactions to be studied from under- and over-saturation by continuous in situ pH monitoring after addition of basic or acidic titrant, respectively, to a pre-equilibrated, well-stirred suspension of the solid powder. The magnitude of each perturbation was kept small to maintain near-equilibrium conditions. For the case of boehmite, multiple pH-jumps at different starting pHs from over- and under-saturated solutions gave the same observed, first-order rate constant consistent with the simple or elementary reaction: Al(OOH)(cr) + H2O(l) + OH^-⇔Al(OH)4^-.
　This relaxation technique allowed us to apply a steady-state approximation to the change in aluminum concentration within the overall principle of detailed balancing and gave a resulting mean rate constant, (2.2±0.3)×10^-5 kg m^-2 s^-1, corresponding to a 1σ uncertainty of 15%, in good agreement with those obtained from the traditional approach of considering the rate of reaction as a function of saturation index. Using the more traditional treatment, all dissolution and precipitation data for boehmite at 100.3℃ were found to follow closely the simple rate expression:
　Rnet,boehmite = 10^-5.485{mOH-}{1 - exp (ΔGr/RT)}, with Rnet in units of mol m^-2 s^-1. This is consistent with Transition State Theory for a reversible elementary reaction that is first order in OH^- concentration involving a single critical activated complex. The relationship applies over the experimental ΔGr range of 0.4-5.5 kJ mol^-1 for precipitation and -0.1 to -1.9 kJ mol^-1 for dissolution, and the pHm三-log(mH⁺) range of 6-9.6. The gibbsite precipitation data at 50℃ could also be treated adequately with the same model: Rnet,gibbsite = 10^-5.86{mOH-}{1 - exp (ΔGr/RT)}, over a more limited experimental range of ΔGr (0.7-3.7 kJ mol^-1) and pHm(8.2-9.7).』

1. Introduction
2. Materials and experimental methods
　2.1. Materials
　2.2. Experimental procedure
3. Data analysis and results
　3.1. Boehmite dissolution/precipitation rates
　　3.1.1. Kinetic analysis from relaxation technique
　　3.1.2. Kinetic analysis from TST
　3.2. Gibbsite precipitation rates
　3.3. Discussion
4. Summary and conclusions
Acknowledgments
Appendix a. Boehmite rate data
Appendix B. Gibbsite rate data
References