A mixture of 70 g. (0.36 mole) of pure 1,4-aminonaphthol hydrochloride and 2100 cc. of water at 30° in a 5-l. flask is stirred for a few minutes in order to dissolve most of the material and then treated with 100 cc. of concentrated sulfuric acid. The mixture is heated to the boiling point until all the precipitated amine sulfate has been brought into solution. The solution is somewhat pink. The hot solution is poured rapidly through a large funnel (without a paper), which has been warmed on the steam bath, into a 5-l. round-bottomed flask containing a filtered solution at room temperature of 70 g. (2.4 moles) of potassium dichromate in 1 l. of water. The flask is shaken to mix the contents thoroughly. The quinone separates at once as a mass of fine, yellow needles. After cooling to 25° the material is collected, washed with water, and dried at 30–40°. The crude product is dull yellow; it melts at 124–125° to a dark liquid and weighs 53–55 g. (Note 1).

The crude naphthoquinone is warmed gently on the steam bath with 1.5 l. of ether, when it rapidly dissolves and leaves in suspension a slight amount of dark, fluffy material. The solution is shaken for ten minutes with 10 g. of decolorizing carbon; it is then filtered, and the ether is distilled from a steam bath until crystals begin to form. The solution is then allowed to cool undisturbed, and the clear canary-yellow prisms which separate are collected and washed with ether. The mother liquor is clarified by shaking as before with 7 g. of decolorizing carbon, filtered, and evaporated to a small volume until crystals begin to separate. The crystals are again washed with ether, and the mother liquor is clarified and evaporated once more. The final crop of material is dull in color but yields a pure product on recrystallization. All the material is of a high quality and melts at 124–125° to a clear yellow liquid; the yield is 44–46 g. (78–81 per cent of the theoretical amount) (Note 2).