2,2′-Biquinoline-4,4′-dicarboxylic acid dipotassium salt trihydrate is a hydrated dipotassium salt of 2,2-biquinoline-4,4-dicarboxylic acid.2,2′-Biquinoline-4,4′-dicarboxylic acid dipotassium salt trihydrate (dipotassium salt of 2,2 -biquinoline- 4,4 -dicarboxylic acid trihydrate) may be used as ligand in the aerobic oxidation of alcohols (primary, secondary and benzylic) in the presence of palladium catalysts. 2,2′-Biquinoline-4,4′-dicarboxylic acid dipotassium salt trihydrate is a hydrated dipotassium salt of 2,2-biquinoline-4,4-dicarboxylic acid. 2,2′-Biquinoline-4,4′-dicarboxylic acid dipotassium salt trihydrate (dipotassium salt of 2,2 -biquinoline- 4,4 -dicarboxylic acid trihydrate) may be used as ligand in the aerobic oxidation of alcohols (primary, secondary and benzylic) in the presence of palladium catalysts.