FIELD: chemical technology. SUBSTANCE: invention proposes a method of countercurrent positive displacement of aliphatic carboxylic acid (carbon number is from one to five) from filtering "press cake" containing aliphatic carboxylic acid. Mother liquor retaining by aromatic polycarboxylic acid has concentration of aliphatic carboxylic acid 5 000 p. p. m. by weight or less (as measured by weight of the presence aromatic polycarboxylic acid). This method is useful for production of crude terephthalic acid which is used after refining for synthesis of complex polyesters. The latter are used in textile and plastic industry. EFFECT: improved method of producing. 5 cl, 4 tbl
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