2 3 pyridine or quinolinedicarboxylic acid diester with an acid having an ionization constant pk a of less than 3 0 followed by isolation of the product as the free acid or an acid salt application_number US 63159490 A description one of the embodiments of the present invention relates to a method for the preparation of acid salts of formula i substituted and unsubstituted 2 3 pyridine and quinolinedicarboxylic acids by hydrolyzing a formula ii 2 3 pyridine or quinolinedicarboxylic acid diester in the presence of water and an acid having a pk a of less than 3 0 at a temperature between about 50 u00b0 c and 110 u00b0 c cooling the heated mixture to a temperature between about 20 u00b0 c and 40 u00b0 c washing the cooled mixture with a volatile chlorinated hydrocarbon an ether or a water immiscible alcohol adding to the washed mixture 1 1 39 oxybis 2 methoxyethane 2 5 8 11 tetraoxadodecane or 2 5 8 11 14 pentaoxapentadecane and separating water to obtain the formula i 2 3 pyridine or quinolinedicarboxylic acid as the acid salt and optionally dispersing said acid salt in water or aqueous base to obtain the formula i 2 3 pyridine or quinolinedicarboxylic acid the method of the present invention is especially.