Abstract: Dicarboxylic acids, e.g., adipic acid, are prepared by reactively distilling and hydrolyzing admixture of a C.sub.1 -C.sub.4 alkyl aliphatic dicarboxylate and water, e.g., dimethyl adipate/water admixture, in liquid phase, in a distillation column, the lower end of which distillation column being charged with a gel of a crosslinked styrene/divinylbenzene resin bearing sulfonic acid substituents, the amount by weight of divinylbenzene comprising such resin ranging from 1% to 12% based on the total weight thereof and such resin having an exchange capacity of from 3 to 6.5 milliequivalents H.sup.+ /gram of dry resin, and including introducing the dicarboxylate/water admixture into the middle region of the column, withdrawing dicarboxylic acid from the base thereof and overhead distilling the alcohol of hydrolysis.