alumina in the form of granules having many fine pores, used to adsorb water and various gases.
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British Dictionary definitions for activated alumina
a granular highly porous and adsorptive form of aluminium oxide, used for drying gases and as an oil-filtering material and catalyst
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012