No abstract

No abstract

The effect of pH and temperature of aqueous solution on hydration of MgO in a batch laboratory reactor was investigated. The experiments were carried out at the temperatures of 120 and I40 "C, pH of cool solution was changed from 10 to 13. It was found that even a small amount of added base substance influences remarkably the size of Mg(OH), crystals. Increasing of pH of aqueous environment causes the decrease of the size of crystals. The increase of the temperature increase dimensions of crystals. This effect is more important at higher alkalinity of the solution.

The diffusion coefficient of Cr(III) determined by chronopotentiometry in the molten system NaF-AlF 3 -CrF 3 was found to be D(Cr(III)) = (5.28 ± 0.14) × 10 −5 cm 2 s −1 . The molar ratio CR = n(NaF)/n(AlF 3 ) was 1.4, which allowed us to perform measurements at 900 • C. When oxygen anions were present in the melt, chromium was deposited simultaneously with aluminium at the cathode, and the apparent diffusion coefficient related to Cr(III) was too high by two orders of magnitude. This may be explained by the formation of oxofluoro complexes of chromium and aluminium. The solubility of Cr 2 O 3 was studied in the above-mentioned melt at 900 • C by two methods: chemical analysis of solidified samples and by chronopotentiometry. It was found that saturation was achieved after several hours, and the concentration of chromium was (177 ± 6) ppm, corresponding to (258 ± 9) ppm Cr 2 O 3 .

No abstract

No abstract

No abstract

No abstract