PREPARATION OF NAPHTHALIC ACID

PURPOSE:To recover an expensive dichromate easily and improve the purity of the aimed substance useful as an intermediate for a dye, pigment, etc., by oxidizing an acenaphthene with an aqueous solution of the dichromate, and reducing the unreacted hexavalent chromium after the reaction. CONSTITUTION:One mole acenaphthene is oxidized with preferably 1.7-3mol dichromate in an aqueous solution thereof, and the unreacted hexavalent chromium in the reaction solution is then reduced to give the titled compound of high purity. The reduction is carried out by using a reducing agent, preferably an alcohol. The amount of the reducing agent is the theoretical amount or more alcohol based on one mole dichromate expressed in terms of the dichromate of the remaining unreacted hexavalent chromium and 30/n moles or less (n is the number of the hydroxyl groups in the molecular formula).