0.05-0.1mg. of organic dibasic acids was placed in a small test tube with 1-2mg. of polyphenols, such as resorcinol, cathecol, hydroquinone, phloroglucinol and pyrogallol, one drop of conc. sulfuric acid added and heated in an oil bath of 130° for 5 minutes. The reaction product was dissolved in a small amount of alkali and submitted to paper partition chromatography (solvent, BuOH:H₂O:AcOH=5:4:1, allowed to stand quietly for 4-5 days after shaking). In the case of resorcinol, phloroglucinol and pyrogallol, strong fluorescent substance of fluorescein- or umbelliferon-type is assumed to be produced and Rf value and spot of fluorescence specific to each organic acid were shown by radiation of ultraviolet rays. Among over 20 substances tested, the strongest spot of fluorescence was shown when 1, 2-dicarboxylic acid, such as citric, maleic, phthalic, succinic and tartaric acids, was reacted with resorcinol. When the reaction products which are known for their color reaction are put to paper chromatography, more accurate identification can be carried out.