An improved apparatus for dual-flow countercurrent extraction was constructed. Further, a simple method to evaluate the extractor was developed, by which the effective plate number could be calculated by a couple of measurements of fractional recoveries. To find the optimum operation condition, an apparatus with a shorter column (10 cm in length) was prepared, the efficiency of which was evaluated as being about one plate per cm of the column length by the method. It was also shown that the distribution constant of a compound could be calculated from the fractional recoveries measured by dual-flow countercurrent extraction. The distribution constants, thus obtained, agreed with values determined independently by liquid-liquid chromatography, which settled theoretical correlations between chromatography and extraction.
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