Water → 5,12-Dihydro-2,9-dimethylquino(2,3-b)acridine-7,14-dione

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To 200.0 g of polyphosphoric acid (118%) was added in portions with stirring at 80° C. 50.0 g (133 mmol) of 2,5-bis(p-toluidino)terephthalic acid. The stirred mixture was irradiated in the microwave oven for 2.0 minutes, during which time the temperature rose to 230° C. The reaction mixture was cooled to 150° C. and drowned in 400 g of methanol with vigorous stirring. The resultant methanol suspension was heated at reflux for one hour, cooled to 60° C., added to 800 g of water, and heated at 60° C. for 30 minutes. The solid component was collected by filtration, washed with 12.0 liters of water, and reslurried with water. [A sample of the crude pigment was collected at this point for X-ray analysis.] After 50.0 g of 50% aqueous sodium hydroxide was added, the alkaline slurry was heated at 90-92° C. for two hours. The solid component was collected by filtration and washed with 12.0 liters of water. The resultant presscake (280 g total, with a pigment content of 40.0 g) was reslurried with water. After adjustment of the pH to 9.0, the slurry was heated for two hours in an autoclave at 140° C., then cooled to room temperature. After adjustment of the pH to 4.5, the slurry was treated with an emulsion of 2.0 g of an anionic surfactant, 25 g of a petroleum distillate, and 40 g of water and stirred for three hours at 45° C. The solid component was collected by filtration and washed with 6.0 liters of water. The presscake was dried overnight in an oven at 60° C. to give 38.0 g of pigmentary quality 2,9-dimethylquinacridone. X-ray diffraction patterns of both the dried acid crude (collected as described above) and the finished pigment were similar to the diffraction pattern of a commercially available 2,9-dimethylquinacridone pigment (i.e., QUINDO Magenta RV-6832 from Bayer Corporation) prepared by a conventional heating method.

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