The different behavior of 5-hydroxytetracycline from tetracycline on the complex formation in spite of the similarity of both complexes in X-ray diffraction patterns, and the difficulty of complex formation of 7-chlorotetracycline, are suggestive of the hindrance effect of 5-hydroxy or 7-chloro group for the formation of complex lattice. Applying the above properties, tetracycline is separated from 5-hydroxytetracycline as the sulfate-succinimide complex, and tetracycline and 5-hydroxytetracycline are separated from 7-chlorotetracycline as their oxalic acid, sulfate-oxalic acid, sulfate-hydantoin and sulfate-succinimide complexes. 7-Chlorotetracycline is recovered as the hydrogenmaleate or the hydrochloride from the mother liquor.

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