SOLUBILITY OF ALUMIMA IN HYDROXIDE - SALT MELTS Oleg G. Zarubitskii and Igor N. Skryptun V.I.Vemadskii Institute of General and Inorganic Chemistry National Academy of Sciences of the Ukraine, 32-34 Palladina Ave, Kiev-142, Ukraine, 03680 ABSTRACT Used method of isothermal saturation solubility of aluminium oxide in alkali and alkaline-salt melts has been investigated at temperature range 673 - 873 K. It was determined that solubility of AI2O3 in the order of melts LiOH - KOH - NaOH - (0.5KOH - 0.5NaOH) are increased. The effect of temperature on the AI2O3 solubility in alkali melts are described of the equation of straight line In C = A - B/T, where C is concentration of the AI2O3 in the melts, mole fract., A and B are constants. It was indicated that when alumina is dissolved in alkali melts, the solutes are alkaline meta-aluminates. The salt additions of sodium chlorine, potassium chloride, sodium carbonate and sodium, nitrate to sodium hydroxide melt are decreased the solubility of alumina. It was calculated the thermodynamic parameters of process solubility of aluminium oxide in alkali hydroxide melts. INTRODUCTION In the past melts of alkali hydroxides and their mixture with salts were widely used in industry for removing alumina-based ceramics from metal surfaces (1). Besides the regularity of process solubility these systems are of interest for ionic melts chemistry. Only a few papers addressing the interaction of aluminium oxide with alkali metal hydroxides have been published (2 - 6). Goret and Tremillon (2) measured the solubility of alumina in a molten eutectic mixture of sodium and potassium hydroxides at 500 K. They proposed that alumina dissolved with chemical interaction and production of sodium meta-alumunates. In (3 - 6) the kinetics of interaction of aluminium oxide with alkali hydroxides by differential thertmogravimetric method are reported. It was shown that in this process the only products are alkaline meta-aluminates. However, in the literature there are no data on the solubility of alumina in alkali and alkaline-salt melts. This investigation was undertaken to examine the process in this systems. Proceedings of The Electrochemical Society, PV 1999-41, 368-375 (1999) DOI: 10.1149/199941.0368PV © The Electrochemical Society ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 207.241.231.83 Downloaded on 2019-04-29 to IP