countercurrent extraction

However, as a pure raffinate can be obtained with countercurrent extraction, it is not necessary to apply a temperature gradient to the lower part of the column.

Fractionation of liquid mixtures can be achieved by countercurrent extraction and this can be improved by imposing a temperature gradient on the column which causes refluxing to occur.

After unsuccessful experiments with complex countercurrent extraction machines and liquid-liquid chromatography methods where the liquids move in opposite directions, Martin hit on the idea of using silica gel in columns to hold water stationary while an organic solvent flows through the column.