PURPOSE: To economically obtain the title high-purity compound useful as a chelating agent for separating a small amount of metal by taking advantage of being ampholyte by making crude hydroxyquinolinecarboxylic acid into an aqueous solution, adjusting the solution to a pH in a specific range to remove impurities, further changing pH, precipitating and separating hydroxyquinolinecarboxylic acid.
CONSTITUTION: Crude hydroxyquinolinecarboxylic acid consisting of hydroxyquinoline, hydroxyquinolinecarhoxylic acid, a mixture of alkaline metallic salt thereof, etc., is first made into an aqueous solution. The amount of water added is 3-50 times, preferably 5-20 times as much as the reaction mixture by weight. The aqueous solution is adjusted to pH6.5-10, preferably pH7-9 to precipitate unreacted hydroxyquinoline. Then hydroxyquinoline is removed from the aqueous solution, the aqueous solution is incorporated with a water-soluble acid such as sulfuric acid and made into pH2-6, preferably pH2-4. Consequently, the aimed compound is precipitated, separated and obtained in high purity.
MITAMURA SHUICHI
INOUE HIROHARU
NIPPON STEEL CHEMICAL CO