Solubility of corundum in supercritical water

Isothermal (670–700°C) solubility of corundum in supercritical water, within the stability range of corundum as a phase of the system Al₂O₃-H₂O, has been determined by the weight loss method. Experiments were performed in the pressure range 2.5 to 6 kbar in cold seal hydrothermal equipment at 670 ± 5°C using gold tubing. The overall uncertainty of the solubility values obtained was 8%. Experiments in the pressure range 10 to 20 kbar were performed in a piston cylinder apparatus at 700°C using sealed gold capsules held by supporting steel containers. The overall uncertainty of the solubility values obtained was estimated to be 10%.All data could be fitted by the linear equation S_ppmAl2O3] = ?12.37 + 7.24 · p_kbar] with correlation coefficient r = 0.9963. Separate fits of hydrothermal and piston cylinder results yielded a small difference between the two data sets, which is due rather to the experimental uncertainty than to the small temperature difference.