was refluxed by vigorous stirring at this point the amorphous phase converted to a boehmite suspension after continuous vigorous stirring for about two hours a stable sol solution is obtained the stirring could be ceased without inducing instability in the sol solution the resulting sol was stable and clear it had a ph of 3 25 equal quantities of atsb and deionized water containing a small quantity of nitric acid were separately dissolved in equal quantities of s butyl alcohol the two solutions were mixed together by dropping slowly the water phase into the atsb phase slowly while vigorously stirring the solution was then aged for an additional two hours finally the sol solution was obtained the solution was not completely stable the concentration of aluminum ions was 0 2m which was the same composition of water molecules contained within the sol the sol solutions obtained from each of the above two methods were transferred to plastic petri dishes which were uncovered and placed in a humidity controlled box at room temperature the slow drying thus initiated was continued until transparent xerogels were formed the dried gels were fired at 500 u00b0 c for at least two hours non transparent unsupported al 2 o 3 membranes were obtained.