5.0 g of crude 1-nitroanthraquinone containing dinitroanthraquinones having a purity of 81% and containing 8% of 1,5-dinitroanthraquinone, 4% of 1,8-dinitroanthraquinone and 7% of other dinitroanthraquinones and being free from anthraquinone and 2-nitroanthraquinone (0.016 mole of 1-nitroanthraquinone and 0.0032 mold of all the dinitroanthraquinones) was hydrogenated in the same way as in Example 5. The reaction was stopped when the amount of hydrogen absorbed reached 0.0816 mole, and the inside of the flask was purged with nitrogen. The amount of hydrogen absorbed corresponded to the sum of the amount of hydrogen required to convert the nitro group to an amino group (0.0672 mole) and 90% of the amount of hydrogen required to convert 1-aminoanthraquinone to its hydroquinone derivative (0.0144 mole). The reaction mixture was filtered in a stream of nitrogen to separate the catalyst and insoluble materials from it. The filtrate was oxidized with air at 20° to 30° C. for 2 hours with stirring to afford 3.2 g of 1-aminoanthraquinone having a purity of 98%. The yield of the product was 88% on a purity basis. The resulting 1-aminoanthraquinone contained about 1% of 1,8-diaminoanthraquinone and only traces of other diamino isomers.
