15. A portion of kaolin weighing 0.2480 g was dissolved, after separation of silicic acid, the solution was diluted to 250 ml in a volumetric flask. Aluminum 8-hydroxyquinoline was precipitated from 20.00 ml of the resulting solution. After drying, a precipitate weighing 0.1038 g was obtained. What is the mass fraction (%) of aluminum oxide in kaolin? Mol. mass (Al(C9H6ON)3) 459.44; they say mass (Al2O3) 101.96.

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